When measuring ambient light with a gray or white card
for white balance, keep in mind that your camera does not need to focus on the
card. In white balance ambient
light reading mode—or whatever your camera calls this mode—it will not
focus anyway since it is only trying to read color temperature values, not take
a picture.
The important thing is to put your lens close enough to
the card to prevent it from seeing anything other than the card. Three or four
inches (about 75 mm to 100 mm) away from the card is the correct distance for
most lenses.
Be careful that your lens
does not cast a shadow onto the card in a way that lets your camera see some of
the shadow. This will make the measurement less accurate. Also, be sure that
your source light does not make a glare on the card. This problem is not as
common because most gray cards have a matte surface; however, it can still
happen. You may want to hold the card at a slight angle to the source light if
the light is particularly bright and might cause glare.
Finally, when the light
is dim, use the white side of the card (if your camera supports white) since it
has more reflectivity. This may prevent a bad reading in low light. The gray card may be more accurate for
color balancing but might be a little dark for a good measurement in dim light.
If you are shooting in normal light, and your camera supports it, a gray card
is best for balancing. You might want to experiment in normal light with your
camera to see which you prefer.
Keep on capturing time...
Darrell Young
Darrell Young
See my Mastering The Nikon DSLR books at:
http://www.photographywriter.com/NikonBooks.asp
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