Flash systems for dental photography

June 1, 2005
In my last column, I talked about the different features of the single lens reflex digital camera that affect how light gets to the computer chip inside the camera.

In my last column, I talked about the different features of the single lens reflex digital camera that affect how light gets to the computer chip inside the camera. This month I want to expand on one of these factors - flash systems.

All digital cameras come with an “on board” flash. This is the flash located either on the top of the camera, or on the left side. For digital SLR cameras, the flash is usually a “pop up” style, and a button must be pushed to open it. Point and Shoot style cameras usually have a visible flash, which is located on the top or left side of the camera. While flash systems that come with a camera may be sufficient for recreational use, they are not always adequate for dental photography. For a digital camera to focus efficiently on a subject, it must be able to read the contrast found in the image. The better the image is illuminated, the faster the camera will focus. This is especially true for Point and Shoot style cameras. If you have ever tried to take an arch shot with a Point and Shoot style camera - and the camera just keeps hunting for the focus - then you know to what I am referring. The computer chips found in the most recently released cameras are more sensitive, and require less light to focus. But additional light is still needed for intraoral photography.

For digital cameras, the most common flash system used in dentistry is a ring flash. A ring flash emits light 360 degrees around the lens. This provides illumination to the subject from all directions. It is designed for up-close photography. This is different from the on board flash found on digital cameras. The on board flash gives additional light from only one direction, usually from the top of the lens or from the left side. This causes problems in two areas. As previously mentioned, it makes it difficult to take intraoral pictures. The light from the flash bounces off the cheek and lips while very little light actually enters the mouth. When a photo of a smile or a photo taken with retractors is used, the left buccal corridor will be fine but the right buccal corridor will be dark. The ring flash eliminates these problems. The ring flash emits light from all sides so sufficient light enters the mouth for intraoral photos. It also lights up both sides of the mouth evenly. But, as with everything, bad comes along with the good. The ring flash can do the job almost too well. While its job is to illuminate the entire field from all directions, the ring flash also will eliminate all shadows. This means the slight texture and anatomy, found particularly on anterior teeth, will not be seen. So teeth and veneers may appear to look “flat.”

A twin flash solves this problem. A twin flash has a ring that attaches to the end of the lens like a ring flash. But it only has two flashes located on opposite sides. These flashes can usually be rotated around the ring and on their own axis, so they can be located in almost any position. I keep mine at the 9 and 12 o’clock positions, and pointed straight ahead. This provides light to both sides of a patient’s smile, and provides sufficient light to illuminate an arch. But it does not remove all shadows. A photo of a smile taken with a twin flash will look much more natural than a smile taken with a ring flash. The color quality will be the same, but even the slightest texture will be visible. The down side to a twin flash is its cost. Depending on the model, a ring flash will cost between $200 and $400. Meanwhile, a twin flash will cost from $700 to $1,100. I have both Canon flash system models that I use with my Canon 20D digital SLR camera. I suggest the twin flash if it fits your budget. Both the Canon ring flash and twin flash also will fit on Canon G series Point and Shoot cameras. For compatibility of Fuji and Nikon ring-twin flashes with their respective Point and Shoot cameras, you will need to consult a camera dealer.

Another flash system that should be mentioned is the “flash diffuser” from Photomed. It is designed to fit not only on the Canon G series cameras but other models as well. You will need to contact Photomed to see if the flash diffuser will fit your camera. It is designed to evenly distribute the on board flash of a Point and Shoot style camera in much the same manner as a ring flash. The flash diffuser works well. The down side is that the unit is made only for certain cameras. If you upgrade to an SLR from a Point and Shoot camera, you will have to buy another flash.

Dr. Tony Soileau is a general dentist from Lafayette, La. He has taught digital photography at the Pacific Aesthetic Continuum in San Francisco, the Institute of Oral Art & Design in Tampa, Fla., and the Esthetic Epitome in Charlotte, N.C. He is currently a co-director for the genR8TNext digital photography program. He lectures on the use of digital photography, digital radiography and computerized case presentations, and high-tech marketing. He can be reached at (337) 234-3551, or by e-mail at [email protected]. For more information about digital technology, visit www.tonysoileau.com.

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