On Jun 10, 2014, at 7:14 AM, Andrew Rodney <andrew@digitaldog.net> wrote:
On Jun 10, 2014, at 8:04 AM, Roger Breton <graxx@videotron.ca> wrote:
A few years ago, I purchased such a white material for dirt cheap from BabelColor. Been using it successfully in all my reproduction work ever since.
As far as my testing of such products, it was the best of that type available. In terms of neutrality and Lstar value, it was (is) amazingly good! Too bad it was so expensive to produce and thus is no longer available.
I have a BabelColor WatchYourWhite target, and it really is quite good. Anybody who wants something comparable...for a mere $500, you can buy a 2" square of Spectralon. And for less than $5,000, you can buy a 5" x 5" multi-step Spectralon target with 12%, 25%, 50%, and 99% swatches. (Prices have increased radically. I seem to remember just a few years ago that the multi-step target was closer to $1,000.) However...both the WatchYourWhite target and Spectralon are overkill for almost all photographic purposes. A styrofoam coffee cup is similarly spectrally flat, but about 80% reflective. Better, because of its near-conical shape, you can use it to sample light from all angles with a single exposure. And you can fit it over the lens to integrate the light from the entire scene. If you're making your own profiling target, PTFE thread seal tape, layered sufficiently that it's opaque, makes a great patch to include in the target. It's not Spectralon and it's quite delicate...but your camera won't know the difference. But, lastly...well, the most effective objective way to normalize white balance and exposure both is by shooting a chart (the ColorChecker Passport is perhaps ideal), profiling a UNIWB gamma 1.0 development of that chart, and querying the resulting profile to determine where the white point lies. You can then re-develop the image with the figures the profile tells you and have a perfectly white balanced, perfectly exposed photograph. ...but, alas, not with Adobe's RAW development engine.... Cheers, b&