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Dental Learning Centers - www.DLCenters.com - (425) 557-7788

Dental Learning Centers | Dental Vision - Dental Photography Resource eNewsletter - September 2010
Dennis Braunston

Dennis Braunston

Founder,
Dental Learning Centers

Experienced, concise, and over 18 years of digital dental camera technology experience, the founder of Dental Learning Centers brings new meaning to dental photography education. As a Nationally recognized mentor, speaker, product developer and author, Dennis has lectured and conducted AGD digital dental photography workshops at various national and regional dental conferences.

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Dental Learnign Centers

Dental Learning Centers
www.DLCenters.com
(425) 557-7788

Dental Learning Centers

Dental Photography Challenges:
Unusual lighting situations.

Controlling your camera

Imagine pushing a magic button that allows you to see three dimensionally through a tooth...you see caries, cracks, and more...

I was recently giving a photography course at Dr. Ernie Casares, San Diego, California. When we were finished he showed me a very cool gadget called a MicroLux TransIlluminator. He puts its condensed LED light behind the patients tooth. It turns the tooth from opaque to translucent, revealing cracks, craze lines and fissures. The event is a real wow! The tooth lights up like a translucent Jack-O-Lantern. It is said to reveal cracks, caries, sub-gingival calculus and root canal orifice. I am not a dentist but might find it thrilling to see a root canal orifice. Oh well...but I digress...

We thought it would be exciting and informational to take a picture of the event for documentation and patient show and tell. But we found it to be challenging.

MicroLux Transilluminator LED Light placed behind tooth Illuminated tooth

You have to have some working knowledge of the cameras controls and translate what the picture is telling you. In essence, we were trying to photograph a bright light, like a star in the night sky. The images using the cameras close up settings did not provide a good picture but after several attempts and adjustments, we figured out the camera's optimal settings:

I knew right away to turn the camera's flash off but the tooth was "blown out," too bright (over exposed) to see anything of value. It was also true viewing it with my eyes; it was a bit too bright to see a lot of detail.

The camera has two controls; these are aperture and shutter speed. In combination they affect depth of field and how much light is allowed to come through. We put the camera in "aperture" priority (Av) which tells it the size of the opening that lets light come in (like the size of your pupil) and the camera decides on the shutter speed. Initially, the camera results were not good; it caused the lighted tooth to be over exposed. We want to see the correct exposure on the bright light but the camera was balancing the entire picture. So the tooth was over exposed.

An analogy would be a performer on a stage being lit by a spotlight. A majority of the surrounding stage is dark. You take a picture and find that the performer, the subject you want to see, is over exposed, they look white. It is not the cameras fault; it simply balances the amount of white to dark and sets an exposure. The opposite occurs when the background has a majority of a white background and your subject in the final picture looks too dark. This may occur when you are in the snow or have white sand behind the subject. [Turn the Exposure Compensation to the plus side]

The solution was to use the cameras "exposure compensation [Ev]." This feature over-rides the shutter speed and or aperture settings, making them either shorter or longer than what is normal for the camera. So, if you want the picture darker, which was the case because the lit tooth was over exposed (too white), you go from zero to the minus side. We went -2 (minus 2) and got great results. In the snow, turn the Ev to the plus side.

Settings:

  1. Aperture priority (put your camera in Av or A)
  2. F-stop 5.6
  3. ISO was 80
  4. Flash Off
  5. Exposure compensation at -2 or close to that
  6. Normal lighting in the operatory
  7. Stay steady due to slower shutter speed
  8. Zoom to see about 8 teeth

Other situations where camera knowledge comes to play are VelScope Photography and taking portraits of people with darker complexions.

http://digital-photography-school.com/ev-compensation-explained