Basic Techniques of Clinical Photography

Liu, Feng; Li, Yi; Shi, Xiaorui

doi:10.1007/978-981-13-1622-7_4

Feng Liu²,
Yi Li² &
Xiaorui Shi²

1331 Accesses

Abstract

The excellent clinical photography requires coordination among the photographer, assistant, and the patient. Only fine coordination lead to the efficient photography and reducing discomfort of the patients.

Access provided by Autonomous University of Puebla. Download chapter PDF

Intraoperative Photography

Standardization in Photographic Documentation

Photographic Principles of Medical Documentation

The excellent clinical photography requires coordination among the photographer, assistant, and the patient. Only fine coordination lead to the efficient photography and reducing discomfort of the patients.

Standard clinical images can be taken by the clinician or the trained assistant following the clinical photography criteria. However, in order to reflect special needs in diagnosis, treatment planning, and execution, the clinician must be the photographer to convey the thought process.

The photographer: have to be acquainted with dental clinical photography criteria, cameras and auxiliary tools, clinical tools, parameters and skills. In addition, an adequate sequence should be developed to minimize application of the instruments such as retractor, contrastor, and mirror to reduce the discomfort of patients. The photographer should be able to guide the assistant for preparing and assisting during dental photography.

The assistants should possess the basic knowledge of dental photography and be familiar with axillary tools for clinical photography. In addition, the assistants should be determined but gentle during retraction, reflection, and other procedures. At the same time, the assistants should comfort the patients to acquire their cooperation during clinical photography.

The patients compliance plays an important role in the process of taking oral clinical images. The necessary images can be affected by the location, modality, and the types of restorations etc. The size of orifice, the range of mouth opening, and the degree of coordination can determine the quality of many clinical images as well.

Basic Procedures of Dental Clinical Photography

In order to take excellent dental clinical images, we need to know basic photographic techniques and the criteria.

A series of preparations should be carried out before shooting to make the process in an order. For an overall understanding of clinical photography, the basic processes should be introduced prior to learning specific techniques.

Basic procedures of dental clinical photography include [1, 2]:

1.
Preparations
1. (a)
  Communicate with patients, create a harmonious environment, patients consent for clinical photography.
2. (b)
  Determine images to be taken and plan the sequence of shooting based on the individual case.
3. (c)
  Assure the camera at working condition and correct setting.
4. (d)
  Arrange all the auxiliary supplies in a convenient location
2.
Photography
1. (a)
  Adjust the lens to the appropriate ratio according to the desired frame.
2. (b)
  Adjust the aperture, shutter speed, and flash intensity to control the exposure and field of depth
3. (c)
  Arrange the patient to a comfortable and appropriate position for dental photography
4. (d)
  The photographer and the assistant take the appropriate position for photography.
5. (e)
  The photographer guides the assistant(s) to expose the target field by with the retractors, contrastors, mirrors, and other auxiliary tools
6. (f)
  The soft and hard tissue, contrastors, mirrors, and other auxiliary tools should be kept clean and dry
7. (g)
  The photographer evaluate and visualize the field and guide the assistant to make necessary adjustment.
8. (h)
  The photographer evaluate the field through the viewfinder, pay attention to the layout and perspective
9. (i)
  With a manual focus setting, adjust the distance between the camera and the object to achieve clear focus through the viewfinder
10. (j)
  Magnify the image to check the focus and composition of the image, retake aif necessary.
3.
Arrange images after shooting
1. (a)
  Export, group, and classify the images according to the patient and treatment process
2. (b)
  Evaluate and minimally adjust the images with the Photoshop software without alteration of originality.
3. (c)
  Both original and the adjusted images must be kept
4. (d)
  Share the images with the patient, dental technician, and provider(s) as needed for effective communications.

The Frame and Ratio

How to decide the oral clinical photography is standard? The most direct and simple judgment standards are as follows. First, the content of the images is reasonable. Second, the images can reflect the lesion situation, the diagnosis, design and treatment accurately. Third, the viewer would clearly know the information photographer want to convey. In fact, it is a matter of the scope of photographic composition. It is the most basic issue of photographic composition.

The Frame

Composition design is the soul of photography, it can reflect the photographer’s thoughts. A completely different effect can be obtained by different selections and frames for the same object.

The essence of the composition scope is comprehension and concision. Comprehension refers to the a sufficient frame for the composition, including all the information, which is relatively easy to achieve in the composition. Concision means intentional controlling the frame to discard the unnecessary information. The common problem in the composition is complexity. The subject will be submerged in the complex foreground and background and the photo losses its effectiveness when the frame is overextended (Figs. 1 and 2).

The purpose of dental clinical images is to reproduce the patients’ oral and maxillofacial soft and hard tissue accurately to include in medical record and promote communications between doctor, patient and technician. The “concision” principle should always be kept in mind when shooting. Images, which are not concise, could not clearly and accurately convey the ideas of the photographer (Figs. 3 and 4).

With the rapid increase of the resolution of the DSLR cameras, Images that were captured by a high resolution digital cameras can be cropped more extensively without compromising the final resolution and quality. This feature has reduced the difficulties of photography.

However, one should intentionally learn to assess the frame if the goal is continuous improve in clinical photography, because it is the first step of photographic composition. In order to assess correct frame, in detail understanding of the subject prior to photography is necessary such as patient’s basic information, diagnosis, design, and treatment plan, so that the photographer determines the core information to be captured and expressed. Only when the frame is fully controlled can we further study and apply the principle of more in-depth photographic composition.

The image should reflect the photographer’s idea.

Image is determined by the mind of the photographer, rather than by the cameras in hand.

For the macro lenses used in clinical photography, the ratio is an important parameter to control the frame [3].

The Ratio

The ratio, also known as magnification ratio, is the ratio between the size of the projection in the image and that of the object.

When the size of the projection on the photoelectric sensor the same as the actual object, the magnification ratio becomes 1:1. If the size on the sensor is the half of the actual size, the shooting ratio is 1:2. And so on. There are many ratios available e.g. 1:2.4, 1:18 and so on.

The ratio determines the absolute size of the projection formed on the photoelectric sensor. For example, a 10 mm object, the 1:1 projection on the sensor will be 10 mm, and in 1:2 it will be 5 mm on the sensor, and the 1:2.5 image will be 4 mm on the sensor, and so on.

The frame is also directly related to the area of the photoelectric sensor. The area of film SLR camera and full frame (FX) photoelectric sensor of digital SLR cameras are both 36 mm × 24 mm. Images taken by these two cameras in 1:1 ratio is the object size of 36 mm × 24 mm. And 1:2 images is the object within the size of 72 mm × 48 mm.

The digital SLR cameras that were widely used in clinical photography have minor difference in size of the sensors depending on the manufacturers (Fig. 5). The sensor of Nikon DX format cameras is 24 mm × 16 mm, both the length and wide are 2/3 of the FX format. So there is 1.5:1 difference between the frame of DX and FX format. 1:1 image taken by DX format camera is the object area of the 24 mm × 16 mm, 1:2 image captures the area of the 48 mm × 32 mm.

The sensos are smaller in Canon DX format, 22.3 mm × 14.9 mm, and the difference between the FX and DX format is 1.6:1. Images taken at 1:1 ratio are the object within the area of 22.3 mm × 14.9 mm, 1:2 image are the object within the area of the 44.6 mm × 29.8 mm.

Based on the specific camera, one can assess and set up the magnification ratios for standard clinical photography. For example, Nikon D300s (DX) can be set to 1:18 for frontal profile, 1:3 for full arch frontal, 1:2.4 for maxillary anteriors frontal, 1:1 for closeup tooth images (Fig. 6).

How to Decide the Frame

The content and the frame of each image should be determined by the photographer based on the individual cases. For doctors who do not have the experience of clinical photography, “standard of clinical photography” of dentistry or similar field can be great references.

1.
In the field of oral medicine, the first routine clinical images were taken in the orthodontic doctors. And the orthodontic profession has a very mature image specification (Appendix 1);
2.
For professional cosmetic dentistry, American Academy of Cosmetic Dentistry (AACD) standard of beauty image specification is a relatively highly recognized in the international arena. It is worthy of reference. The images listed in this specification can reflect the information of cosmetic dentistry (Appendix 2);
3.
The European Society of Cosmetic Dentistry (ESCD), another influential international aesthetic dental association, has formulated a specification more focused on the overall diagnosis and design. It is obviously different from the AACD specification and recognized by many European doctors (Appendix 3);
4.
Chinese society of esthetics medicine (CSED) drew up the first set of the standard of oral esthetics in China in 2016. The author of this book, along with his team, has been responsible for the drafting of the standard. He also helped founding the Committee composed of 29 experts. The expert of CSED and the Standing Committee discussed and established the specification, and popularized it through around the country by nationwide lecture series (Figs. 7 and 8).

Clinicians can refer to these specifications when they lack of experience in assessing the frame and composition. But in the specific application, they should summarize a suitable frame and ratio based on the equipment they use. Because different camera has a different size, which will directly affect the magnification ratio and the frame.

The method is very simple. As previously mentioned, with the understanding of the concept of the shooting ratio, the relationship between the camera sensor and the shooting ratio, you can calculate the actual frame of different cameras at each magnification ratio (Table 1

Table 1 Frame (or image frame) of different of cameras corresponding to different magnification ratio

Full size table

). No matter what the object is, the frame can be directly determined by the magnification ratio.

In actual operation, we can also try this: we try to capture an image according to the standard, when we should note the settings when an “ideal” photo was taken. Each macro lens has a window (Fig. 9) that shows the magnification ratio and the object distance. These parameters should be memorized. For example, we shoot an image with parameters read from windows 1:2 and 0.4 m (Fig. 10). Next time when taking the same image, we only need to rotate lens and determine the ratio of 1:2, then focus and take photo. As long as there is no change in ratio, we should get a clear image at 0.4 m distance. The image should be at adequate frame.

Of course, when you are experienced, you can shoot flexibly by adjusting the frame and composition according to the actual situations. Thus images will reflect the characteristics of the case and doctor’s idea to the maximum extent.

Moreover, in order to reserve space for cropping, we can set the frame slightly oversized. For example, the most appropriate smile image magnification ratio should be 1:2.4, but in order to make room for the future adjustment, we can shoot with the ratio of 1:2.5 to get a slightly larger image.

Exposure and Depth of Field

The Basic Principles of Exposure Settings

Exposure refers to the total amount of light received by the photoelectric sensor (CCD or CMOS). Appropriate exposure is the most basic requirement to meet the standard of clinical application.

The details can be accurately expressed with an image with appropriate exposure. From the brightest region to the darkest, all the details are visible with gradual transition. When the photoelectric sensor receive excessive amount of light, it will lead to overexposure and too bright image (Fig. 11); While if the photoelectric sensor received too little light, it will cause underexposure and the image is dark (Fig. 12). Either overexposure or underexposure will result in loss of details and unsatisfactory images [4].

As explained in the previous chapter, four factors affect the exposure: ISO, aperture, shutter speed, and illumination (flash lamp). The following principles have to applied during setting the exposure parameters in dental clinical photography:

1.
In order to achieve the best image quality, the ISO is usually set to the lowest value.
2.
Dental clinical photography requires sufficient depth of field. The smaller aperture, typically smaller than F22, should be maintained during photography.
3.
A tripod is impractical in clinical photography due to postural restriction. In order to prevent fuzzy images caused by unstable hands, the shutter speed should be faster than 1/100 s in general, 1/125–1/180 s for the best.
4.
Achieve appropriate exposure with appropriate illumination.

If the preliminary image is underexposed, exposure can be increased by reducing the aperture index F (increasing the aperture), slowing shutter speed, or increasing the intensity of flash intensity. Conversely, if it was overexposed, it can be decreased by increasing the aperture index F (reduce aperture), or increasing the shutter speed, or decreasing the intensity of flash. Adjustments should be made until a satisfactory image was obtained.

It is worth mentioning that any of the exposure parameters is changed, the others should be adjusted accordingly. The macro flash is an important variable in clinical photography. A ring flash is relatively stable and easy to control and is a better option for beginners. Macro twin flash is more complicated. Even with consistent intensity of twin flashes, the lighting will change with the distance, the angle of the flash head, the reflection methods, and other conditions. It is relatively difficult to obtain a consistent exposure condition.

Moreover, there are no absolute objective criteria for appropriate exposure. In daily photography, we can use a light meter to test the light conditions to obtain a relatively “correct” exposure conditions. However, we feel it with our eyes more often. Just like people have different feelings about beauty, each person’s feeling about accurate exposure will be different. “Relatively accurate exposure” and “special exposure effect” of the image can give people different feelings, but also can reflect the photographer’s idea and mentality (Figs. 13 and 14).

“Correct exposure” in oral clinical photography should be “close to reality”.

“Histogram” function of LCD display can help us to relatively objectively evaluate the exposure. The histogram displays image exposure accuracy by waveform on axes. The horizontal axis represents the brightness level, from the left to the right is 0 (dark) to 255 (bright), 256 levels in total. The vertical axis represents the number of pixels of each brightness level, the higher peak means the number of pixels of this brightness level is more, which means this brightness level takes up more area in the image. Connect the vertical axis point forms a continuous waveform histogram. From the histogram of the horizontal and vertical axes, we can reasonably assess the proper exposure, whether the image is well balanced, and whether it is beyond the dynamic range of digital camera.

An image with proper exposure will show a curve distribution from left to right without pixel overflow to both ends of the histogram (Fig. 15). The peak of a histogram of an underexposed image will be skewed to the left. Since most of the pixels are clustered on the left side, the right wing is decreased significantly to form a “right slope” (Fig. 16). On the contrary, overexposed images’ histogram is skewed to the right. The left side of the pixel is little or none, there is a blank from 0 (the dark) to the point the curve starts. Image is very bright and may have light reflection area, known as the “left slope” (Fig. 17).

There is a way to compensate the risk of inaccurate exposure, using RAW format to shoot.

Generally, image saved in JEPG format file is a compressed file with loss of information. The format is smaller, easy to store, copy, but the image details will be lost and can not be edited and adjusted. TIFF format is an uncompressed file but too large to operate. The image details are not lost but additional editing the adjusting are not allowed. The RAW file contains the original information after the image generated by the photoelectric sensor and prior to camera processor. The images in RAW format can be processed by graphics processing software, including adjustment of exposures.

However, compare to the commonly used JPEG and TIFF format, RAW files takes more time to open and process. In order to solve this problem, many digital cameras allow users to take images in JPEG and RAW format at the same time (Fig. 18).

As the camera processing speed became faster and the memory card capacity getting larger with more affordable prices, this approach is more widely accepted. Take images in JPEG and RAW format image at the same time, allow us to use the conventional image processing software to organize and edit JPEG files. When you need to get fine edit or process defected images (such as images with bright or dark details missing caused by incorrect balance or exposure), you may use the RAW file to solve the problem.

Selection of the Exposure Mode

As mentioned before, the exposure mode of the SLR digital camera usually includes automatic mode (Auto mode), programmed mode (P mode), shutter priority mode (S mode), aperture priority mode (A mode) and full manual mode (M mode). And many cameras also have portrait, vision, movement, night scene and so on, which is so called “point and shoot” mode for exposure. The low level and intermediate camera does not have shoulder screens generally and the exposure mode can be selected by rotating the dial (Fig. 19). The higher end camera has the MODE button for selecting shooting mode and shows the current status on the shoulder LCD screen (Fig. 20).

Auto mode and P mode are both automatic exposure mode with the camera automatically adjusting the aperture and shutter speed to achieve appropriate exposure. The camera in these two mode usually automatically set exposure parameters at intermediate value, especially aperture is moderate or large in general. Instead of being less than F22 which we desire, most of the time the aperture will be set up in F5.6, F8. So the depth of field is often compromised when shooting with Auto mode and P mode (Fig. 21). Therefore, only the beginners who are completely not familiar with the operation of the camera can try the automatic mode at first. Then gradually give up the automatic mode after you know the camera well, and learn other shooting modes.

In shutter priority mode (S mode), the shutter speed is set by manual and the camera automatically detects the illumination to determine the aperture. This model still could not effectively control the aperture resulting in either too big aperture or too small depth of field. So it is not recommended.

In the aperture priority mode (A mode) refers to setting the aperture based on the need of depth of field, then the shutter speed will be automatically set by the camera to obtain a proper exposure. Aperture priority mode assures the depth of field and relatively easy to handle, so it can be a good option for beginners.

But in some cases, the shutter speed automatically selected by camera in aperture priority mode (A mode) is too slow and cause trembling when shooting. The full manual mode (M mode) is recommended under this situation. Moreover, some special effect, such as intentional under or over exposure, can only be achieved by full manual mode (M mode). Hence, it is very necessary to master the full manual mode (M mode).

Full manual mode (M mode) refers to manually setting the aperture, shutter speed, flash, and other conditions to get ideal exposure. Full manual exposure mode (M mode) combined with the concept of manification ratio may allow standard exposure achievable i.e. consistent exposure on the same object at different time [5].

Exposure Parameters and Shooting Scope

Full manual exposure mode is recommended in oral clinical photography. Each set of exposure parameters can get the best exposure effect only at one certain shooting distance, i.e., each set of exposure parameters corresponds to one shooting distance.

As mentioned before, the distance and magnification ratio of macro lens is closely related. Macro lens window not only shows the shooting ratio, but also shows the corresponding shooting distance (Fig. 10). So in fact shoot ratio and the exposure parameters is corresponded, too. Furthermore, when using the same digital SLR body, the shooting scope and the shooting ratio is also one-to-one match. So the exposure parameters and the shooting scope are also corresponded.

Basically, when the photographer decides the range of the object for shooting, the shot ratio and shooting distance have been determined. And there is also a set of optimum exposure parameters to achieve the most suitable depth of field and exposure. For different cameras, the exposure parameters for the same shooting scope will be different. We can explore, determine the most appropriate exposure parameters in each scope for specific equipment. Then remember them and form personalized standards.

In actual shooting, the photographer should determine the shooting scope first according to the specific situation. Then convert it to shooting ratio and corresponding exposure parameters. Rotate camera lens to this shooting ratio, set the corresponding exposure parameters and then shoot. Images taken by this method may have a consistent level of exposure. This is meaningful for store the data of the multiple treatments, preoperative and postoperative and follow-up clinical data is very significant (Figs. 22 and 23). Otherwise, if the exposure parameter of each time is different, the data will lack of comparability and scientific nature.

Position and Holding

Patient Position

Before taking a clinical image, you need to choose a position that is comfortable for the patient, and also conducive to the operation of the assistant and the photographer.

Sitting on a dental chair is not a good choice for taking a facial portrait cause it is likely to cause a head tilt. Let the patient to stand or sit in a chair, keep the head, back, shoulder integrity. Image captured this way could correctly reflect the relationship between aesthetics and the horizontal plane (Figs. 24 and 25).

When taking close up extraoral images, the patient can still maintain this posture. You also can make the patient lying on the dental chair adjusted to 45°, but ensure the head and shoulder are straight (Fig. 26). Ask the patient turn left or right when shooting the left and right side image according to the needs. The photographer can also adjust the position to obtain suitable shooting angle.

When taking intraoral images we need to let the patient lying on the dental chair adjusted to 45°. In this position we can take most of the images: the frontal and Lateral occlusal images, the anterior and posterior dentition images, the individual anterior and posterior tooth images etc.

When taking maxillary dental arch occlusal view image, anterior arch incisal view image or shadematching image, you need to adjust the chair as down as possible, make the patient almost flat, which is more conducive to shoot (Fig. 27).

The Position of Photographer and Assistant

According to the patient’s position, the photographer and the assistant have to find their position that are convenient to take images and comfortable.

If the patient is upright or sitting on the dental chair reclined 45°, the photographer can simply find the appropriate height in front of the patient (Figs. 28 and 29). If the image demands retractions in this position, the assistant stands on the other side of the chair to retract the cheek to expose sufficient area.

In the position that is slightly higher than the previous one, you can continue to take the mandibular dental arch occlusal view image. While the patient slightly raise the chin, the photographer stands on one side of the dental chair and shoots from the front. The assistant holding the mirror stand on the other side and keep the view clean and dry with gental air from three way syringe. The second assistant or patient can assist with retractions (Fig. 30).

When taking maxillary full arch occlusal view image, adjust the chair to the patient in an almost flat position. The photographer stands on patient’s 12 o’clock position and shoots from the top. The assistant holding the mirror stands on one side and keep the view clean and dry with gental air. The second assistant or patient can assist retraction. Due to the large frame, the lens has to keep a certain distance from the patent to make the image accommodate the entire dental arch. So the dental chair should be as low as possible to create enough focus distance. If the photographer is too short, standing on a small stool would help (Fig. 31).

When taking the reflected image, the position of the mirror is very important. Only when the mirror and the camera are in a suitable angle, can an image with good composition be obtained. When the assistant holds the mirror, sometimes will have the problem that mirror need to be adjusted or the photographer and the assistant have trouble in coordination. If the photographer has very rich experience in shooting and can hold the camera very stable, he can hold the camera in one hand and hold mirror in the other hand. He can adjust the two hands at the same time to find the best position and angle for the photo. The assistant can provide retraction, defog the mirror, and other auxiliary work.

For left lateral shot of intercuspal position, the patient lays down with head straight and gently pulls the right lips with retractors. The assistant stands on patients’ left side, retracts the left cheek with mirror as far as possible to form a 45° angle to the buccal side of the arch without contact. The photographer should stand on the patient right to shoot (Fig. 32). For right lateral shot of intercuspal position, the patient turns slightly to the right, gently pulls the left lips with the retractor. The assistant stands on patients’ back, retracts the right cheek with mirror as far as possible to form a 45° angle to the buccal surface without contact. The photographer is still standing on the right side to shoot (Fig. 33).

For the lingual or palatal shots of posterior teeth with mirror, the photographer stands on the right. The assistant stands on the left, holds the mirror in position, and blows gently to keep dry, while the patient retract the lip. The patient’s head can be adjusted accordingly to get the best shooting angle (Fig. 34). If the photographer had the ability to hold the camera with one hand and the mirror with the other hand, it will be more convenient to shoot.

Anterior teeth overbite and overjet images are very important in aesthetic dental treatment. The images could be taken while patient standing, sitting or lying on the chair. Make the patient lying with head straight, keep the teeth occluded. The assistant retracts the bilateral lips posteriorly to fully expose the upper and lower anterior teeth. The photographer positions on the patient’s right on one knee, shooting from the horizontal direction. This ensures the stability during photography to get accurate overbite and overjet relationship of anterior teeth (Fig. 35).

As long as no bright subjects present at near left side, the conventional background will appear to be black due to limited depth of field and will not affect the image. Unless severe asymmetry presents, which requires bilateral shots, only one anterior overbit overjet photo is needed.

In the Chap. “Basic Images of Dental Clinical Photography”, we will describe the patient position and assistant position of each image in detail.

Basic Skills in Holding Camera

Whether the photographer is holding the camera properly is closely related to the image is clear or not. When shooting clinical images, holding camera with one single hand to take images is not recommend for most people. It is more secure to hold the camera with both hands. The general principle is handy, convenient and stable.

Photos for oral photography are banner images in general. To take banner images, the photographer usually use the right hand to press the shutter, the palm of the left hand to hold camera, fingers to adjust aperture, focus and other work.

When taking clinical images, the standardized way is adjusting the aperture, shutter and other settings, moving back and forth to focus accurately. So the left is completely used to control and grasp the camera without any adjustment action. So you can hold the bottom of camera body with the palm of left hand and hold the lens with thumb and index finger. Because of the macro lens and macro flash lamp are very heavy, plus a variety of accessories such as shovel bracket, reflective lens direction, significantly increased the weight, the left index finger should be stretched forward as far as possible to make the camera stabile. To enhance stability further, you may also keep the upper arms down naturally and close to the body. Don’t shrug your shoulders. The shoulders will be fatigue when shooting with a shrug of the shoulders for a long time and make it more difficult to stabilize the camera (Fig. 36).

When shooting vertical image, generally left hand is on upper side, right hand is on lower side. You should also pay attention to keep the left arm close to the body.

It is better to hang camera strap on the neck when shooting. Even if the camera is directly held in your hand, you should also wrap the camera strap around the wrist. The specific method is wrapping the camera strap on the wrist, gripping in the part of the hand between the thumb and the index finger and winding two circles and pulling tight. The camera and the right hand are bind together, which can not only reduce the hand tremor, but also avoid accidentally dropping the camera with bumps.

Since most of the clinical images are shot while the photographer standing, the standing posture also has a certain impact on stability. The feet should be slightly open, one-up, one-back, so that the weight of the whole body equally disperse on the feet. If you can rely on some fixed objects, such as the side of the dental chair, and so on, it is better.

Pulling and Exposure

It is necessary for the photographer and the assistant to cooperate with each other when taking intraoral images. If the assistant is skilled, gentle, using pull and reflective plate effectively, maintaining the view dry and clear, it is helpful to take images successfully and reduce the patient’s discomfort.

In general the photographer will take face portrait and extraoral images prior without assistants. Assistants should use this time to prepare accessories for later shooting, such as retractors, background panels and other related accessories, such as mirror panels. This will make the shooting progress go well.

When taking intraoral images, it should find the proper position for the patient as well as the photographer and assistant first. The photographer should set the shooting mode and corresponding shooting ratio, aperture, shutter speed, flash intensity and other parameters according to the specific image and then apply retractors, contrastors and mirrors.

Placing Retractors

When taking an intraoral image, a retractor is usually needed to fully expose the visual field. Proper pulling is the basic skill for the assistant to master.

First you need to select the appropriate retractor with proper shape and size. If the retractor is too large, it is difficult to put it into the patient’s mouth, and also will increase the discomfort feelings.

Although a small retractor is easy to the placed into the mouth, but is not conducive to the exposure of visual field.

In principle, it should choose the smallest retractor that is able to clearly expose the visual field. Small finger-shaped retractor is relatively minimal and will decrease the discomfort of the patient. Thus it is preferred in many images.

Retractor can make the patient uncomfortable. Doctors should apply some Vaseline or oil on patients’ lips painted to avoid laceration. When placing and rotating the retractor, you should pay attention to avoid jamming teeth or oppressing gum or mucosa. As for large retractor, never pull from the side directly, no matter what the final position is. Allow the patient to slightly open mouth, place the retractor into the mouth from the lower and front direction of corner of the mouth (Fig. 37), and then gently rotate and pull the device to desired position (Fig. 38).

For beginners, who must repeatedly practice how to place a variety of retractor into their own mouths. Learn how to place, how to pull to avoid pain and discomfort. Try to shorten the time of application of retractors and other auxiliary equipment and reduce the times of putting in and pulling off to reduce the patient’s discomfort when shooting in clinical practice. All products should be placed in the reach of the assistant. Try to avoid the situation that one device has been placed in the mouth, while the other one is not available.

Sometimes we can try to teach the patients to pull themselves, which makes patients to actively participate in the shooting procedure and avoids pain due to improper pulling. It would let the assistant operate contrastor and mirror more liberally and keep the visual field clean and dry.

Full Pulling

In order to fully expose the soft and hard tissue in the mouth, it is necessary to use a device to pull the lip, cheek tissues way. The retractor should be way from the teeth, so to make better exposure of buccal space and allow the light reach the posterior teeth to make the anterior and posterior teeth in the image clear (Fig. 39). The retractor would be large enough to pull lateral and front lips at the same time. Or else the lips will form dumbbell-shaped, this will affect the image (Fig. 40).

When using black contrastor to take dentition image, we need to use the retractor to pull the lip and buccal tissue. When taking maxillary image, pull the lip and buccal angle upward. As for the mandibular image, pull toward angle below. Try to expose the gingival tissue as much as possible but also to avoid the formation of “dumbbell type central gum”. Patient do not opens mouth too wide, as long as the black background board can be placed would be enough (Figs. 41 and 42).

Pulling for the Image of Arch Image

To photograph the image of the dental arch occlusal plane, it is also required to use the retractor to pull the lip and buccal tissue. With the use of reflective plate to make sure the entire arch can be reflected.

The modified semilunar retractor is useful for this image. Put the long side toward the work side and put it into the mouth to proper position. You can let the patients pull themselves. If you shoot the upper dental arch, pull the retractor angle upper outward; if you take the lower dental arch, pull it angle downward (Figs. 43 and 44). You can also use small finger-shaped retractor, O fork retractor or o fork black background board and other auxiliary equipment to take the image to get better results (Figs. 45, 46, and 47).

Try to select the convex shaped mirror, it is more likely to take a complete image of the arch (Fig. 48). When placing the reflecting board, the back end of the mirror should not contact to the teeth, otherwise the double image can be formed (Figs. 49 and 50). We also should keep the mirror from damage by avoid friction between the mirror and the teeth.

Retracting for the Posterior Occlusion Image

Complete posterior occlusion image might be the most difficult one to take; it often makes the patients feel uncomfortable. Choosing auxiliary tools properly and proper placement can reduce discomfort to a certain extent.

Taking posterior occlusion image with buccal retractor is a relatively easy way (Figs. 51 and 52). The buccal retractor’s ability to expose buccal gingival tissue is weak than that of mirror. But the shooting difficulty will be substantially reduced, and the feelings of patients will be significantly improved. We should try to use the buccal retractor to shoot if possible.

For the cases of Orthodontics and prosthodontics focus on “teeth”, the buccal retractor is recommended. While as for the cases of periodontics and implantodontics focus both on teeth and gingival tissue, the buccal mirror is the right chioce.

The right way to put the buccal mirror is very important:

The correct operation is: put the mirror in when mouth is open, and then let the patient bite the teeth together, then turned the mirror to buccal side.

If it is necessary for the case and the actual patient’s oral conditions permit, we should try to take the most complete images include the distal of second molars. The buccal mirror must be used to pull buccal soft tissue to the side, but may not contact with the buccal side of teeth. Keep the buccal mirror away from the buccal side of second molar. It should also choose the mirror with maximum width that the patient can bear, so as to make it easier to get the most comprehensive reflection. If the mirror is narrow, it is very easy to cause the direction of mirror and the tooth inconsistency and caused incomplete image.

Using a larger retractor to pull the opposite side lips, the purpose of this pulling is just to keep the lips stable, so there is no need to pull very hard (Fig. 53). If there is no pulling, the opposite side lips may be sinking, forming a triangle shape, which will affect the shooting results (Fig. 54).

Before composed with the camera, the photographer should composed with eyes first by observing the reflection. Tell the assistant to adjust the mirror to the most appropriate position. Usually this coordination between doctor and assistant is rather difficult. If you can hold camera with one hand and hold the mirror to pull and adjust with the other hand, it will slightly reduce the shooting difficulty.

Of course, no matter buccal retractor or mirror, if the actual conditions do not allow or the cases do not ask, it is of no need to shot the most complete image. If the second molar is not included in treatment, most of the time it is not necessary to capture the second molars, or else it may increase the pain to the patients, resulting in their fear, sick or even refusing to cooperate with shooting afterward.

Retracting for Lingual, Palatal Images of Posterior Teeth

Mirror and the retractor are also needed when taking lingual, palatal images of posterior teeth. It is only need to pull the lips and bucccal tissue on working side. You can let the patient pull himself after retractor is placed. Gently pull the lips and buccal tissue as far as possible to avoid contact with the teeth. The assistant or the photographer put the mirror on the lingual or palatal to reflect and the teeth. Adjust the angle of the mirror according to the need of the reflection. When taking lingual image of the mandibular teeth, use the mirror to push the tongue (Figs. 55 and 56).

Keep the Visual Field Clean and Dry

It should try to keep the visual field clean and dry whatever the image is taking. This is an important work of the assistant.

In general, the assistant placed the retractor, had the patient pull, then gently blow the teeth to keep them dry. This move is to remove the saliva and bubble to avoid stain, black spot or reflective point in the image. But do not blow too hard, otherwise will cause dehydration or sensitivity.

When using the mirror, we must gently discontinuously blow it with air to remove the water mist, otherwise it will affect image. You can soak the mirror in warm water before use, this will help to prevent the formation of water mist.

Composition and Focus

After the preparation, the photographer should first compose with eyes. If you could not get an ideal composition image with eyes, you may not get it with camera either. You need to guide the patient and the assistant to adjust. Only when you see the appropriate composition with eyes, can you use the camera to capture.

Composition

In addition to shooting scope, clinical photography should also pay attention to shoot from the “horizontal vertical” perspective.

It should arrange the main part of the object in the middle of the image, and keep it horizontal vertical. This composition method might be a little dull, inflexible, lack of beauty for common photography, but it is the most standardized and rigorous for serious clinical medical case. In the cases of aesthetic treatment, the composition will help to observe and analyze the aesthetic factors, but will not cause human error.

The optical viewfinder of SLR camera usually has a cross mark for focusing, which will assist in composition (Fig. 57). Firstly, put the subject in center and avoid the image offset, keep it bilateral symmetry by referring to the pupil line and facial midline (Fig. 58). Secondly, try to keep the occlusal plane horizontal and the dental midline vertical, prevent the image deflect (Fig. 59). Because the doctor usually stands on the side of the dental chair, he turn his body to place the camera in the relatively proper position with the teeth (Fig. 60).

It is very likely that there is a certain level of horizontal angulation in actual shooting. In order to standardize the image, it should be rotated and cut in the post process. As mentioned before, it is possible to spare room for the post processing when determining the shooting ratio. For example, when you need take images with 1:2.4 shooting ratio, you can shoot with 1:2.5 to spare room for the precise adjustment later.

It is necessary to emphasize that the cutting and rotating work of post processing will result in the loss of the pixel. And if the deflection angle is too large (Fig. 61), it is impossible to cut out of complete image, so the composition scope will have to be reduced, which sometimes will affect the shooting result (Fig. 62). Therefore, we should try to keep horizontal vertical as far as possible to get a standardized image, reduce the dependence on the post processing.

It should be noted that the “horizontal vertical” principle of composition means three-dimensional “horizontal vertical” (Fig. 63). First the projection of the dentition in coronal plane should be “flat”. The shooting angle should also be parallel with “sagittal” and “horizontal” plane at the same time. These too points are very important, which is the matter of “perspective”.

“Perspective” is an important issue in composition. As mentioned in previous chapters, even for the most common shooting objects, different perspectives of the photographer will bring the viewer different experiences (Figs. 66 and 67). In order to achieve the purpose of “higher than life”, the photographers usually avoid the straight composition, the most conventional perspective. They look for special and creative perspective, the images would be innovative and intriguing (Figs. 64 and 65). In recent years, UAV photography which becomes more and more popular is actually using the perspective that people usually could not reach (Figs. 66 and 67). The recently popular unmanned aerial vehicle just takes photos in a fantastic perspective out of manual reach (Fig. 68).

Different from other types of photography, medical clinical photography requires authenticity, scientific nature, reflecting the object accurately and real. Therefore, the clinical photography requires a “horizontal vertical” angle of view, to prevent the occurrence of deformation.

The shooting angle should be parallel with the horizontal plane, which is the same as the dental X-ray radiograph principle. Image taken from this perspective is realistic and objective, the occlusal plane was basically a straight line, that is the most standard clinical image (Figs. 69 and 70). When the shooting angle is not parallel with horizontal plane, the lens position is too high or too low, will the form overlooking or looking up perspective. Thus the authenticity of image will be affected due to stretching or compressing. The aesthetic evaluation based on this image will be imprecise.

When the perspective is too high, the occlusal plane becomes obvious downward convex curve (Fig. 71). Though the image was not real, but the downward convex anterior teeth cutting edge curve has been strengthened, formed an “exaggerated” appearance. Some doctors use such images from this perspective after treatment (Fig. 72).

On the contrary, when the angle is too low, the occlusal plane may be upward convex curve (Fig. 73). The image is not real, also not beautiful, anterior teeth cutting edge curve become anti arc. It is a failed image (Fig. 74). But in the actual shooting, this situation appears a lot. When the patients feel uncomfortable during the pulling, they usually raise their heads unconsciously. If the photographer did not consciously correct them, or adjust their position, this problem will be caused.

The photographer needs to guide the patients to the adductor jaw when shooting. Meanwhile pay attention to raise camera angle consciously to avoid shooting from a low perspective.

The shooting angle also need be parallel with the sagittal plane, not left or right offset, otherwise it may affect the authenticity of the image. Shooting from the offset perspective will expand the same side of the image, compression on the other side of the image (Fig. 75). It is impossible to analyze and judge the bilateral symmetry with such an image, while the symmetry analysis is the most basic baseline analysis in many aesthetic analysis and design.

The aesthetic analysis of digital smile design (DSD) is very popular in recent years. It is focus on the relationship between teeth-lips and face. The analysis about facial midline, teeth midline, tooth width proportion, length width proportion, and the position of teeth cut edge is the core of DSD analysis and design (Fig. 76).

The photographer needs to observe the patient’s face and teeth carefully before shooting. If there are asymmetric or deflection problem, it should be reflected objectively demonstrated. If the patient is symmetrical, it should try to keep the real symmetry in the process of shooting.

When taking facial images, it is recommended that the patient comb the hair back to expose the ears. When making composition, the photographer can take the ears as a reference to determine whether the shooting angle is parallel to the sagittal plane. After the shooting, we can also use the ear as a reference to check the symmetry of the image to determine whether the image can be used for aesthetic analysis and design (Fig. 77).

Doing analysis about aesthetic characteristics and parameters such as the dentition midline and tooth width proportion based on an image with poor perspective could possibly get a wrong conclusion (Fig. 78).

Focusing

As mentioned before, each set of exposure parameters has an accurate shooting distance. Therefore we need to accurately find the distance to get proper exposure and accurate composition. It requires mastering the correct focus method to achieve this goal.

Focus has two major categories: auto focus and manual focus.

The shooting scope of auto focus is random. The camera automatically adjusts the ratio to focus, which is relatively easier for most photographers. But in the oral clinical photography, object color is relatively uniform, which is not conducive to accurate auto focus. The camera is prone to repeatedly adjust the focus like a bellows.

More importantly, this process has changed the shooting ratio, also changed the composition scope. This will result in the mismatching between image range and exposure parameters, and inaccurate composition scope and exposure. In a random shooting distance, the AF mode, although can change the telescopic lens until the focus is clear, but the actual shooting distance and exposure parameters do not match, resulting in excessive exposure or insufficient exposure. Therefore, the automatic focus is highly undesirable in clinical photography.

Manual focus mode is divided into two categories: manual adjust focus ring, or adjust the shooting distance.

Manual adjustment of focusing ring is applied in most macro focusing photography. It is rapid and accurate, but will still bring the mismatch between shooting scope and exposure parameters. So it is not recommended too.

Manual focus and adjustment of the shooting distance is most recommended.

This method does not change the magnification ratio of the lens, does not change the shooting ratio. It finds the most accurate location of focus by moving the camera back and forth. This manual focus is suitable for standard oral digital image.

Specific operation method is as follows: adjust the body and lens to the manual focus mode first (Figs. 79 and 80), determine the shooting scope according to the needs, and determine the corresponding shooting ratio. According to this ratio determined a series of exposure parameters including aperture, shutter speed and flash intensity. Find the corresponding shooting distance according to the shooting ratio at the same time. Set the camera near the position, then move it back and forth until the object is completely clear, then press the shutter.

This shooting method is very rare in other areas of photography, the biggest advantage is to ensure that the standardization of the composition scope and the amount of exposure. It is a very scientific photography method.

It is important to avoid rotating the focus ring on the camera lens throughout the shooting process. Or else the shoot ratio will be changed, which will cause the change of composition scope. And the changed shooting distance does not match the preset exposure parameter, therefore caused inaccurate exposure of the image.

The photographer needs to observe with eyes to judge whether the focusing is accurate in manual focus mode. While beginners usually cannot accurately judge, resulting in a blurred image, which requires the photographer to practice, amplification the image in the computer after to observe and enrich the experience.

Enough lighting will help the photographer to focus.

It should avoid the object directly exposing to strong uncertainty light in actual shooting, to ensure that the flash has become the main light source of the macro lens, to make the light intensity and white balance controllable. But it is hard to focus if the light on the object is too weak, which will cause the difficulty of accurate focusing.

Other light sources, such as the light on the dental chair, can be used as a secondary light to assist to focus. But it must be closed at the time of shooting, otherwise it may affect the color of the captured image, at the same time may increase the reflection spot on the teeth. This spot will affect the observation of the tooth details. Some of the lights have auxiliary light for focus, which will be automatically closed when shooting, will not affect the image (Fig. 81).

Many macro lens appeared in recent years have manual/automatic focusing function (M/A) (Fig. 82). Photographers with sufficient experience may try to use this feature, so that the focus is more accurate.

You need to turn the lens focus button to M/A file when using this function. The preparation and the adjustment of the shooting ratio did not change. Use manual focus to move the camera to find the clearest position. At this time, half press the shutter to start auto focus mode, the camera uses its auto focus function may have a further focus range. Since the manual focus has almost reached the focus position, the adjustment range of AF should be very small. The AF here is only to help focus more accurately, but will not have a substantial impact on the shooting ratio, shooting scope, etc.

When using this function, it is very important to set the point of focus. It shall be placed on the most important position of the object, where the color is not uniform, otherwise it may cause focus shift and impossible to take image.

To achieve precise focus, the camera must be as stable as possible. If the camera body trembled or shifted the moment you pressing the shutter, it may cause the focus inaccurate. Limited to clinical positions, most clinical images cannot use tripod. It requires the photographer to hold the camera in a right way and try to control the camera stably.

Digital SLR camera body is relatively heavy, plus the lens and the flash, they will be rather heavy. The photographer needs practice more frequently to achieve stable operation. The photographer will slightly shift when breathing, which will also affects the focusing. So the photographer needs to hold his breath when focusing and shooting.

When the image is captured, it should be immediately checked from the screen. The amplification is necessary for careful examination of the clarity, the image details, and finding possible problems in time.

When the photographer is checking the image, the assistant should not take out the retractor and mirror but keep the shooting posture does not move. If there is a problem with the image, it is convenient to adjust and shoot again. Reduce the times of putting auxiliary in and out of mouth as much as you can to reduce the discomfort of the patient.

Basic Application of Special Camera for Oral Clinic

If you could not grasp the digital SLR camera or want to make daily work more easily, the camera with light weight for oral clinic is also a good choice for the non-aesthetic cases. Eyespecial-II produced by Shofu Japan is currently the most mature oral clinical special camera.

Eyespecial C-II LCD screen has visual signs of shooting scope and shooting ratio. The photographer can use the same idea as the SLR camera. It is very easy to choose the shooting ratio, in order to control the shooting scope. The images can be consistent with the previous standard (Figs. 83 and 84).

Eyespecial C-II has automatic cutting function. It allows shooting a little ahead or behind of the accurate distance, then automatically cut the image according to the shooting ratio. Achieve accurate shooting range control. This makes it easier to grasp the whole shooting process (Figs. 85 and 86).

Eyespecial C-II automatically controls exposure through the automatic ranging and automatic light. The white balance is detected and corrected by the famous Japanese oral color expert Professor Katayama Hikokuro. It could achieve reproduction of color close to the true color. Compared with the general SLR camera system, these functions are the advantages of “medical special camera”.

Eyespecial C-II is equipped with two sets of double point flash (Fig. 87), it will automatic selection of different flash location according to the shooting distance and different objects, different shooting mode: for recent shooting distance, small shooting scope, automatically select an outside flash, reduce the influence of reflected light; for far shooting distance, large shooting scope, automatically select the inside flash, in order to provide enough light for rear arch.

Eyespecial-II has eight different shooting modes, you can choose flexibly according to the needs of clinical photography (Fig. 88):

1.
Standard mode: conventional intraoral images
2.
Surgery mode: the shooting distance is longer than that of other mode, which is beneficial to prevent the pollution of the operation area.
3.
Mirror mode: it is applied to the image when using mirror, the camera shows hints to flip image after taking, and the latter work is reduced (Fig. 89).
4.
Face mode: weak the back shadow (Fig. 90)
5.
Low glare mode: taking images at a more close shooting distance and use a group of flash far from the camera lens, reduce the reflection of the tooth surface, which is conducive to the capture and transmission of micro aesthetic information (Figs. 91 and 92).
6.
Whitening mode: bleaching agent mainly works on enamel, the bleaching effect on dentin is weak. The whitening model uses a large aperture to show color change of teeth surface, contrast effect before and after tooth bleaching records more real. Use a group of flash far from the camera lens to reduce the reflection of the tooth surface, to better present the true situation of the tooth surface.
7.
Tele macro mode: using the tele converter lens to achieve greater magnification, get macro images with more details (Figs. 93 and 94).
8.
Isolate shade mode: automatically convert red lip and oral mucosa to gray after shooting, keep the teeth color, and reduce red color’s interference with teeth (Figs. 95 and 96).

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Peking University Hospital of Stomatology, Beijing, China
Feng Liu, Yi Li & Xiaorui Shi

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Feng Liu
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Yi Li
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Xiaorui Shi
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1st Clinical Division, Peking University Hospital of Stomatology, Beijing, China
Feng Liu

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Liu, F., Li, Y., Shi, X. (2019). Basic Techniques of Clinical Photography. In: Liu, F. (eds) Dental Digital Photography. Springer, Singapore. https://doi.org/10.1007/978-981-13-1622-7_4

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DOI: https://doi.org/10.1007/978-981-13-1622-7_4
Published: 24 April 2019
Publisher Name: Springer, Singapore
Print ISBN: 978-981-13-1621-0
Online ISBN: 978-981-13-1622-7
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