Canon MR-14EX Quick Start Manual page 5

PhotoMed Quick Start Guide
Exposure settings for Before & After bleaching photos
Canon's E-TTL flash metering system is a
terrific convenience when shooting the
wide range of dental photos:
posterior vs. anterior, direct vs. mirror
shots. The camera determines how much
light is necessary and controls the flash
output for a proper exposure.
Before and After (B&A) bleaching photos are the exception to
the rule. We obviously want to show the dramatic change in
the brightness of the smile, but if we use the camera controlled
flash system, the Before photo will be brighter than it actually
is and the After photo will not show the level of brightness
achieved. This is due to the camera detecting that the Before
photo needed more light and the After photo was reflecting
quite a bit more light.
The only way to show the true degree of bleaching in B&A
photos is to set the camera to manual mode and use pre-
determined settings to ensure that the camera cannot attempt
to control the exposure. Listed below are the steps necessary.
Once you have gone through the steps, you can easily set your
camera in a matter of seconds.
1. Set your camera to the M mode (see photo). Set the shutter
speed to 250 by turning the MAIN DIAL (see photo page 1).
2. Set the flash in the M mode by pressing the MODE button
on the back of the flash power pack (see photo page 1).
3. Set the lens to MF (see photo page 3). Decide which lens
magnification you would like to use for your anterior shots
(see photo page 3). For the 40D, a lens magnification of 1:3 is
a good starting point. Once you decide which magnification
works for you, always use this setting. This ensures that the
We suggest that you become familiar with the layout of the LCD displays. Before taking a photograph, glance at the displays and
ensure that the shutter speed, f-stop and flash mode are correct. If you get in the habit of doing this, you will catch any instances
where a button gets pushed or the MAIN DIAL gets turned accidentally before you take the photo at an incorrect setting. Thank
you again for your purchase of the Canon 40D Digital Clinical System.
If you have any questions, please call one of our technical experts at 818-908-5369.
PhotoMed
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I N T E R N A T I O N A L
© 2008, PhotoMed International. All rights reserved
40D - Canon MR-14EX
distance to the patient is always the same and the exposure
will be the same.
Now, the testing begins:
4. Set the f-stop (see photo page 1) to 32 by turning the QUICK
CONTROL DIAL (see photo page 2).
5. Put your eye to the camera viewfinder and move towards and
away from your subject until you see the image in sharp focus.
Press the SHUTTER BUTTON to take a photo. Evaluate the image
on your computer and compare the image to your subject.
If the image is TOO BRIGHT: press the SEL button on the back
of the flash power pack and then press the - (minus) button to
change the power to 1/2. Repeat the photo and evaluate. Keep
lowering the power until the exposure is correct.
If the image is TOO DARK: turn the QUICK CONTROL DIAL to
change the f-stop to a lower number (i.e., from 32 to 29).
Repeat the shot and evaluate. Keep opening the f-stop (to a
lower number) until the exposure is correct.
If the image is JUST RIGHT: make note of the f-stop number
and flash power setting. These are now the settings that you
should always use for your B&A bleaching photos. Be sure to
always use the same lens magnification that you used during
this test. If you change the magnification, your distance to the
subject and your exposure will be different.
page 5
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