In my past columns I have written about the different methods of controlling how much light reaches the computer chip to capture the image. This refers to how bright the image is, too bright, too dark, or just right. This brightness of the image is controlled by primarily by 4 systems. The first is the flash which can vary the amount of light reflected off the subject (what your taking a picture of, tooth, smile, portrait, etc.). After the light from the flash bounces off the subject it passes through the second system which is the aperture. This system is the “size” of the window on the end of lens. The third system the light passes through is the shutter. The shutter refers to the “door” the light passes through 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 contact is the compute chip. The computer chip can be made more or less sensitive to the light. The more sensitive the chip is the bright the image will be.
The mode the camera is in affects how the camera controls the aperture and shutter systems together to affect how bright the image is. There are usually 6 modes for the photographer to choose from on SLR (35mm type) digital cameras. The first mode is Full Auto. It 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. This mode is represented by a “P”. In this mode the photographer can set either the aperture or shutter system. The camera will then set whichever system the photographer does not set. The third mode is Shutter Priority. This mode is represented by “TV”. In this mode the photographer sets the shutter speed and the camera chooses the aperture setting to give the best image. The fourth mode is Aperture Priority. This mode is represented by “AV”. In this mode the photographer set the aperture setting and the camera picks the shutter speed to give the best image. The fifth mode is Manual. His mode is represented by “M”. In this mode the photographer chooses both the aperture and shutter setting. The sixth mode is Auto Depth of Field. This mode is represented by “A-Dep”. In this mode the camera chooses the aperture setting to give the greatest depth of field to have for the subject.
Which mode is used depends on the individual photographer. The two most commonly chosen modes for dental photography are Manual and Aperture Priority. My next few columns will discuss different techniques for photographing dental subjects. I remember when I had graduated from dental school I was confused because every lecturer claimed their technique from composite fillings to root canals was best. I did not know who to believe. Well, I am afraid digital photography is the same way today. Some dental photographers have very strong views as to which mode, camera, lens, etc. is best. My advice is to remember that a perfect image can be captured regardless of the subject, in every mode. You just have to know handle the camera to chose the right settings. I would suggest trying different techniques and using the one that works best in your hands, even if you are told it is not the best way.
My favorite setting, when using a Canon D series SLR digital camera, is Aperture Priority, AV. The Canon D series has a custom function that allows me 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, f-stop, according to whether I am taking a full face image or a smile or intra-oral images. For a full face image I use 6.7 for my f-stop. For any other image, whether it be a smile, retracted smile, or intra-oral image, I set my f-stop to 22. This means both myself and my team only have to remember two settings for all of our clinical images. Tom Hedge, a dentist and master photographer who practices in Ohio uses the Manual mode for all his photography. He prefers to adjust both his aperture and shutter speed for his clinical images. Our mages look identical. We just use two different methods to capture them. So try different methods and chose the one that works the best in your hands. That will be the correct settings.