Choose best method to focus images

Depending on the type of camera you are using, you have two choices when it comes to focusing on an image - manual or auto.

Depending on the type of camera you are using, you have two choices when it comes to focusing on an image - manual or auto. The switch for changing between manual and auto focusing is found on the lens, not the camera body. Both methods have advantages and disadvantages. I will discuss both, and describe how I use them.

Manually focusing on an image is the traditional method used by most dentists, especially if they have used a 35mm camera before they switched to a digital camera. Manual focusing involves a photographer turning and adjusting the focusing ring (or rings) on the lenses so that the image captured will be sharp and crisp. The focusing ring can be preset to points such as 1:1 for a close-up image, or 1:10 for a portrait style image. Organizations such as the AACD have standard settings based on these ratios for the different photographic views required for accreditation. These ratio settings can be found on the barrel of the lens. As the focusing ring is turned, the ratio setting can be noted. The advantage of using manual focusing is that a constant image can be achieved for each setting. This means that both the “before” and “after” images will have the same view. A 1:1, 1:2, etc., setting will give a photographer the same image each time the setting is used with a particular patient. While a constant image view is an advantage to using a manual setting, it also requires a photographer to determine the correct distance from the subject to the lens - the focusing distance. A photographer must position the camera lens the correct distance from a patient’s smile, or arch, so that the image will be in focus. This can be accomplished by noting a photographer’s position, including the position of his or her feet. Each time a particular view is taken (whether it be 1:1, 1:2, etc.), the same stance is duplicated. This will ensure the proper distance from the lens to the image each time.

Using the auto focus feature of the lens allows the camera to focus the lens instead of a photographer doing so. This allows for a focused image regardless of the distance from the camera lens to the image. When the shutter button is engaged halfway, the camera will rotate the focusing ring inside the lens until a focused image is obtained. The camera will alert a photographer once an image is in focus, usually with a “beeping” sound. After hearing this sound, a photographer then engages the shutter button completely to capture a focused image. By using auto focus, a photographer can pay more attention to the subject and not worry as much about taking a blurry image. With auto focus, a photographer usually can take images at a faster pace. The disadvantage of using auto focus is that a second image of the same view may be slightly different if the distance of the lens to the image is not the same. This happens since the image is in focus regardless of the distance.

Are you not sure yet whether to use manual or auto focus? Let’s try to put this matter in simpler terms. If a dentist takes a photo of a patient’s smile that spans from the distal edge of tooth number 7 to the distal edge of tooth number 10 using manual focus, both “before” and “after” images will show the same view if the dentist uses the same ratio setting. In this instance, a dentist has to be the same distance from a patient’s smile for both images to be in focus. If a dentist uses auto focus, he or she does not have to be the same distance for both images. The first (before) image may show lateral to lateral while the second (after) may show canine to canine and still be in focus. As long as a dentist maintains the same distance from camera lens to subject, it does not matter if he or she uses manual or auto focus. The images will be the same. Thus, the issue to address is the importance of both images being the same.

While I use both methods, I keep my lens preset on auto focus. I move to the same position for each view that I take. I focus manually if the camera does not immediately focus. Since I am preset on auto focus, if a patient or I move - or if my eyes are tired - the camera will make small corrections to ensure proper focusing.

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. Soileau 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. Contact Soileau at (337) 234-3551, or at tony@tonysoileau.com. For more regarding digital technology, visit www.tonysoileau.com or www.dentalblogs.com.

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