Exposure in dental photography

This article is part of chapter 1 of the Book “Layers” By Dr. Jordi Manauta and Dr. Anna Salat, available in September 2012 by Quintessence Books. The difference between a beautiful picture and a terrible picture reside most importantly on the lighting.

Regardless the camera, objective or flash brand, every modern “reflex” camera comes with a lightning exposure regulator.

Our suggestion on the equipment is to have a reflex camera capable of communicating with a TTL flash, of course a TTL flash (point flash or ring flash depending on anterior or posterior) and a 105mm objective.

We will do an easy exercise to optimize and understand the lighting in our pictures, this task requires a 10min exercise with the camera and a model or a patient.

We should start programming the camera at f32 (diaphragm), 1:1.5 (focal distance) and 1/200 (speed).

Then we will take 25 to 50 pictures depending on the camera.

The camera should be set at -3.0EV (flash compensation) and take a picture, then move to the next step -2.7EV, take another picture, then at -2.5EV, -2,3EV and so on, until we reach +3.0EV.

Fig.1

The result is a series of pictures from the darkest to the lightest, from these pictures we will choose the best lightning for color analysis and the best lightning for picture presentation and or publication.

Fig.2

One of the first images that is useful for us is found in the “dark” spectrum of the exposure curve. To be more precise we say that the picture is sub-exposed (-0,7EV). In aesthetic dentistry this kind of pictures offer us a clear sight of chromatic structures, more contrast and precise shape event thou the picture is not beautiful.

Fig.3

The same picture with the right exposure (0EV), this image is ideal for documentation and lecturing purposes. We can still see the chromatic properties of the tooth, but not in an optimal way.

Fig.4

An over exposed picture (+0,7EV) is not suitable for any purpose, not for the color matching nor for presentations or documentation, the pictures are completely ruined in this stage because all the colors mix into white.

Fig.5

Taking the optimal “under-exposed picture” on the computer, we can digitally increase the contrast and decrease the brightness and obtain full detail of the color characteristics. The gums will look as if they are about to bleed, but the characteristics on the teeth arise in an awesome way.

Fig.6

With the computer we can make the brightness/contrast trick to better analyze the color in many situations, as shown here with the shade guide.

Fig.7

Fig.8

With the computer we can make the brightness/contrast trick to better analyze the color in many situations, as shown here with the shade guide.

Bibliography

1. Salat A, Manauta J, Devoto W. Achieving a precise colour chart with common computer software for excellency in anterior composite restorations, Eur J Esthet Dent. 2011 Autum, to be released

2. Naoki Hayashi La fotografía digital. Dental Dialogue Spanish edition 2009; vol 3 pg 47-58.

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