ExpoImaging ExpoDisc Reference Manual for Digital Cameras - Manual (Page 5)

ExpoDisc Instruction Manual
v. 4.0. 05/06
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2. Set the indicated exposure with the camera in the “M” manual exposure mode.
3. Take an exposure, or reading through the ExpoDisc to set the custom white
balance. (See 1.f. Where to Aim the camera.)
If your camera does not capture an image in the custom white balance procedure, e.g.
Nikon cameras, then you may want to take an additional exposure through the ExpoDisc
to examine its histogram.
Examine the in-camera histogram of the ExpoDisc image file to verify the exposure is
not clipped in either the highlight or shadow areas. If the histogram appears acceptable,
then you have an acceptable exposure for custom white-balance purposes.
Note. Setting a custom white balance under strobe illumination at an exposure setting
other than that with which you will photograph your subject may produce an incorrect
white balance and colorcast. The difference in exposure could alter the ratio of ambient
light to strobe light, which would effectively change the color temperature of your
custom white balance exposure.
1.h. Where to Aim the Camera for the Custom White Balance Capture
Using the ExpoDisc to set an accurate custom white balance requires the light
illuminating the subject to pass through the ExpoDisc to your camera’s image sensor.
This is easily accomplished in studio, under ambient light, and in certain on-camera
flash applications. Point the camera towards the main light source in studio, or under
ambient light in a direction that will capture the direct and reflected light illuminating
the subject for the custom white balance capture.
1.h.1 Ambient/Mixed Lighting
Point the camera in a direction that allows the light you wish to balance (the light
illuminating your photographic subject) to strike the front of the ExpoDisc. In other
words, stand in similar lighting as your subject and point the camera back towards the
position from which you will take the picture. Using this technique will allow you to
balance the average color temperature of ambient light illuminating your subject,
including light reflected off nearby surfaces, e.g. green lawn, red brick patio, brightly
colored walls, etc.
1.h.2. Landscape Photography
Although the ExpoDisc is an incident tool, the landscape photographer will find it
invaluable in correcting for extreme lighting conditions, e.g. snow scenes, high
elevations, early evenings, etc. Because a landscape photographer’s subject is a vista
encompassing many color temperatures of light, it is impossible to balance to a single
light source. Therefore, it is best to balance to the scene itself, by aiming the camera
towards the scene to be photographed. This technique allows the camera to establish an
average color temperature for the scene, and to preserve the varying shift in warmer and
cooler tones throughout the scene.