In past columns, I have discussed different methods of controlling the amount of light that reaches a camera’s computer chip in order to capture an image. This refers to the brightness of the image, whether it be too bright, too dark, or just right. This brightness is controlled primarily by four systems. The first system, the flash, can vary the amount of light reflected off the subject (whatever you are taking a picture of such as a tooth, smile, portrait, etc.). After the light from the flash bounces off the subject, it passes through a second system, the aperture. This system is the “size” of the window on the end of the lens. The third system that the light penetrates is the shutter. The shutter refers to the “door” that the light passes through, and is located just inside the camera body. The longer the door stays open, the brighter the image will be. The fourth system that the light will make contact with is the computer chip. The computer chip can be made more or less sensitive to the light. The more sensitive the chip is, the brighter an image will be.
The mode the camera is in affects how the camera jointly controls the aperture and shutter systems to affect how bright an image is. On a single lens reflex (35 mm) digital camera, there are usually six modes from which a photographer can choose. The first mode is Full Auto. This is usually represented by a green rectangle or square. In this mode, the camera evaluates the subject and sets both the aperture and shutter settings to give the best image. The second mode is Program, which is is represented by a “P.” In this mode, a photographer can set either the aperture or shutter system. The camera will then set the system that the photographer does not set. The third mode is Shutter Priority, which is represented by “TV.” In this mode, a photographer sets the shutter speed, and the camera chooses the aperture setting to give the best image. The fourth mode is Aperture Priority, which is represented by “AV.” In this mode, a photographer sets the aperture setting, and the camera picks the shutter speed to give the best image. The fifth mode is Manual, which is represented by “M.” In this mode, a photographer selects both the aperture and shutter setting. The sixth mode is Auto Depth of Field, which is represented by “A-Dep.” In this mode, the camera chooses the aperture setting to give the greatest depth of field for a subject.
The mode used depends on the photographer and the type of photo. For dental photography, the two most common modes are Manual and Aperture Priority. My next few columns will discuss different techniques for taking photos of dental subjects. When I graduated from dental school, I was confused because every lecturer claimed his or her technique from composite fillings to root canals was best. I did not know who to believe. Digital photography is much the same today. Some dental photographers have strong views regarding which mode, camera, lens, etc., is best. My advice is to remember that, no matter the mode, a perfect image can be captured regardless of the subject. You must know how to handle the camera so that you can select the right settings. I would suggest trying different techniques, and then use the one that works best for you - even if you are told this technique is not the best.
My favorite setting, when using a Canon D series SLR digital camera, is Aperture Priority or AV. The Canon D series has a custom function that allows you to “fix” the shutter speed so it stays constant in Aperture Priority mode. This means the flash, shutter speed, and computer chip all remain at a constant setting. I simply change the aperture setting (the f-stop), based on whether I am taking a full-face image, smile, or intraoral images. For a full-face image, I use an f-stop of 6.7. For any other image - whether it be a smile, retracted smile, or intraoral image - I set my f-stop to 22. Thus, at my practice, there is a need to remember only two settings for all our clinical images. Tom Hedge, a dentist and master photographer who practices in Ohio, uses the Manual mode for his photography. He prefers to adjust both his aperture and shutter speed for his clinical images. Despite using different modes, the images from Tom’s practice and my practice look nearly identical. So, again, I recommend trying different methods, and choosing the one that works the best with the camera in your hands. This will be the correct setting.
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.
