In my last column, I talked about different flash systems. The purpose of the flash is to throw light on whatever it is you are photographing. Once light has bounced off a subject, it has to be channeled to the camera’s sensor to capture the image. This is the job of the lens, to channel the light. The lens can do other things, too.
Let’s start with a typical digital camera setup for dentistry. The standard type of lens is a macro lens, usually 100 mm in focal length. For purposes of this column, I will be discussing the Canon EF (electronic focus) 100 mm Macro USM (ultrasonic motor) lens. Depending on the brand of camera, your lens may be 105 mm, or something similar. Using the Canon 100 mm Macro lens as our base unit, we will compare other lenses to it. When a lens is referred to as a macro type, this means that the lens is designed to take closeup views of small objects such as flowers, insects, and teeth. For dentistry, the ability to focus closely on small objects is essential. The 100mm length allows us to be eight to 20 inches from a patient yet still take a closeup view, such as a single incisor. A macro lens can take a portrait image that looks just like any other lens was used. But, since the macro lens is designed to focus up close, you need to stand six to eight feet from a patient to get a view of the entire face.
The Canon 100 mm Macro lens is also in the class of lenses rated USM. The lens is driven by electronically controlled magnets that are very smooth and fast. Thus, when the lens - not the camera body - is set to auto-focus instead of manual-focus, it will focus on the subject quickly and smoothly. Another advantage of this type of lens is its ability to be focused manually while in auto-focus mode. This is a huge advantage because, if the patient moves, the lens will make the slight correction for you. This is why I recommend setting the lens to auto-focus even if you manually focus the lens. This assumes that your lens has this capability. Otherwise, you may strip the gears. But, like all things, these advantages come with a price. The first is weight. At my hands-on course, the first thing that team members tell me after they pick up an SLR camera is how heavy it is. Most of the weight comes from the lens. The second disadvantage is price. The Canon 100 mm Macro lens costs approximately $600. There are cheaper macro lenses available that will give you the same quality of image. Sigma makes a 105 mm macro lens that costs about $400. While I do like this lens, it is not smooth enough for me and takes too long to focus. But it is not UL so it is not designed to focus quickly. It is simply a less expensive lens with fewer features. This is how nondental camera stores can sell cheaper packages that sound just as good. Remember that you get less when you pay less.
Another less expensive macro lens is the Canon EF 60 mm Macro USM lens, which comes with the Canon Rebel 350. This camera is a watered-down version of the Canon 20D. Both camera and lens are very nice for the person on a tight budget. But there is something to keep in mind. The 60 mm focal length means that you will have to get close to the patient to take the images, and I mean very close. This could make some patients uncomfortable unless you warn them. Also, since the flash is just about an inch from the patient’s face for some views, be sure to remind the patient to close his or her eyes.
For portrait-type photography, there are more lenses to choose from than I could describe in 100 columns. I have lost track of how many lenses I own and use, but I’ll share two to give you an idea of what’s available. For a simple, inexpensive portrait lens I like the Canon EF 28-80 mm USM lens. It is very light, has quality glass, and focuses quickly. For all-day shooting or just simple team and patient portraits, this is a great lens. My favorite portrait camera, which I consider to be the master of all lenses, is the Canon EF 24-70 Macro USM lens. I use this lens for professional shoots such as swimwear, model portfolios, etc. Because it is a macro, I can get close to the product the model is wearing yet still pull away for full-body poses. This is one lens that does it all. But it has disadvantages. First, the lens is heavy. In fact, it is significantly heavier than other lenses. But, if I have to choose between one lens or bringing a camera bag and changing lenses for each shot, then I don’t mind the weight. At approximately $1,150, it also costs quite a bit as compared to other “dental” lenses. But, if you want an all-purpose lens for portrait, not clinical photos, this is the best one I have found.
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.
