Subject: recommended gray card vendors?
Subject: recommended gray card vendors?
- Subject: Subject: recommended gray card vendors?
- From: Don Hutcheson <email@hidden>
- Date: Sun, 17 Mar 2002 09:35:47 -0500
Jack,
Best solution may be good old DIY. I don't think you need a 'perfect' gray
(whatever that may be) so much as a repeatable one that you can obtain in
sufficient quantity and economy to throw away when it gets worn.
MY SUGGESTION
(long method):
1. At a good art supply store, buy a sampling of gray-looking artists'
boards.
2. Use a spectrophotometer and suitable software (e.g. SpectroCam) to
display the whole spectrum of each sample.
3. Find the one with the smoothest horizontal graph from UV to IR, and/or a
graph that looks closest to the graph measured from the patch you have been
using up till now - e.g. the Macbeth ColorChecker.
4. Buy a relative truck-load of the selected board. Cut a few useful-sized
pieces and store the rest safely where it won't get damaged by light,
humidity, chemicals, etc.
5. Make your profile (or whatever) using this new card to first establish
gray balance.
(short method):
1. Same as step 1. above.
2. Gray-balance your camera on the current reference (e.g. ColorChecker)
then repeat with the new samples.
3. Pick the one that makes the least change to the camera's gray balance,
i.e. the one that performs virtually the same as the ColorChecker.
4. Continue with steps 4. & 5. above.
Even if the sample you choose isn't perfectly gray, your shots should now
always have the same relative gray balance.
FWIW,
Don
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