ExpoImaging ExpoDisc Reference Manual for Digital Cameras - Manual (Page 12)

ExpoDisc Instruction Manual
v. 4.0. 05/06
12
Check the camera’s instruction manual to ensure you are correctly following the custom
white balance procedure. Simple procedural errors frequently lead to inconsistent
results and colorcasts. User defined camera settings can also affect results, such as
color, tone and hue. Firmware updates, monitor calibration and print settings should
also be considered and evaluated when troubleshooting color problems.
3.b. Camera Rejects the Custom White Balance Reading
If a digital camera takes a reading without taking an exposure (e.g., Nikon, Fuji, etc.) in
the custom white balance procedure, then the camera may reject the reading (No Good)
if the custom white balance capture is over, or under exposed. If this rejection occurs,
then adjust the exposure and repeat the custom white balance procedure until the
camera accepts the reading.
The camera may also reject the custom white balance reading if the color temperature of
light is outside the range and capability of the camera to balance (No Good, Over/Under
Error). See 1.k. Poor Color Saturation. Modify the color temperature of light to bring it
within the specified custom white balance range of the camera.
3.c. Correcting for Colorcasts
Because the ExpoDisc is a professional tool it must be treated like any other professional
tool, with a proper respect of what it can do when used properly, and what can result if
used improperly.
Taking a picture with an improper white balance will yield an undesirable colorcast.
Red, Green, Blue, Cyan, Magenta or Yellow colorcasts may result from improper use of
the ExpoDisc. Most colorcasts result from improperly aiming the camera while setting
the custom white balance, or from failing to properly follow the camera’s custom white
balance procedures.
In general, a bluish colorcast will appear in the image if the custom white balance
capture incorporated warmer light than that which illuminated the subject at the time of
image capture. Conversely, a red or yellow colorcast will occur if the custom white
balance was set to a cooler light source than that which illuminated the subject at the
time of image capture.
3.d. Photographing in Mixed Light
White balance settings are stored as color temperatures, and digital cameras are limited
to setting a single white balance color temperature for any given shot. Using an
ExpoDisc, a photographer can set a single white balance to an average color temperature
of two or more divergent light sources. However, an individual light source may still
dominate the color of light illuminating particular portions of an image. To the extent
that any portion of an image is illuminated by light that differs from the camera’s set
white balance, that portion may show a colorcast.
In a diffused mixed light environment, aim the camera in a direction that will expose the
ExpoDisc to the multiple light sources during the custom white balance capture.