Tim Zoltie presents a few (of the many) concepts and principles relevant to dental photography.

often see articles discussing top tips in dental photography, but I believe what must come first is an understanding of the basic principles of photography and an in-depth knowledge of the impact they may have on the depiction of the subject matter.

Aperture, shutter speed and ISO

A photographer must balance aperture, shutter speed and ISO to ensure the correct amount of light hits the camera sensor for an accurately exposed image. Each of these variables can impact the final photographic image in different ways.

An image shot at a slow shutter speed may cause motion blur, an image shot with high ISO may cause grain, and an image captured with a large aperture will create a shallow area in focus (depth of field).

While portraiture may benefit from creative application of a shallow depth of field, in dental photography we want the whole of the subject to be in focus. It is therefore important to shoot at a small aperture (eg f/22) to ensure a wider depth of field. A small aperture inevitably means there is less light coming through the lens, meaning adjustments must be made to ensure enough light gets to the camera sensor to expose the image correctly. This can be done by increasing the ISO (sensitivity of the sensor to light), slowing down the shutter speed (time the sensor is exposed to the light), or using flash. The latter is the chosen method due to its ability to be angled in to the area of interest and ability to provide a consistent colour temperature output.

Perspective, patient positioning and angle of view

Perspective in a picture is concerned with depicting the volumes and spatial relationships of the subject(s) on a flat surface. Perspective is governed by the subject to camera distance, and angle. Using a standard 50mm lens on a full frame digital single lens reflex camera (DSLR) for an extra oral view of a face for example, will result in a distorted perspective. The person’s nose will appear larger than in ‘real life.’ Shoot the same subject on a 105 or 100 mm macro lens, and the face will have a more ‘normal’ appearance.

Principles of perspective can also affect size and it is therefore important that the angle of capture is horizontal to the plane of focus. For example; simply varying the angle of capture when taking a picture of a central incisor may alter the perception and measurement of the crown length. A change in angle between the pre and post treatment photographs can therefore lead to an inability to achieve accurate comparative measurements following treatment.

Colour balance

We see in colour, and accurately re-creating colour while understanding its impact is fundamental. Accurate colour reproduction is achieved through colour balancing; the adjustment of colour intensity so that objects that appear white for example, are rendered white. For a photograph to be a true and accurate record of the subject, what the camera saw must be matched with what our brain sees. This is especially important when measuring the results of teeth whitening following aesthetic dentistry treatment.

To gain consistent and accurate colour rendition, a photographer must use a neutral grey card during the photography process. This provides a measured reference white point, which can be applied to all images taken within the same lighting scenario. A colour calibrated monitor is also recommended.

Standardisation

Standardisation is key to ensuring credibility and authenticity through the use of standard operating procedures. In dental photography, standardisation ensures that any changes appearing in a series of photographs over time are changes to the subject matter and subsequently not caused by any alterations in the capturing process.

The photographer must be able to provide a standard operating procedure that has been followed and a method of practice suitable to document treatment accurately and legitimately. This must also include variables such as scale, positioning and background.

Conclusion

There are many basic principles of photography that are valuable to learn for anyone undertaking dental photography. Many of these principles go beyond the scope of this article, however it is important to know not only how photographic techniques and settings effect an image, but why. This enables users to understand the outcomes of adjusting camera settings and to apply this knowledge in everyday practice.

Dental photography is an intriguing and in-depth profession, governed only by how the user wishes to depict his/her subject for the purpose intended. 


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