On Nov 4, 2013, at 12:15 PM, Marc Sitkin <mbs@digitalmomentum.com> wrote:
I'm using a rather old color checker and RPP64 for profiling, and am getting peak errors of deltaE 11, and average errors of over 4. Is it possible this is related to the age of the target, and if so, how long should one be kept before replacing?
A lot will depend on your workflow. It would be trivial to get those kinds of errors with bad technique. If you have (access to) a spectrophotometer, you can do two things. First, you can compare your ColorChecker against any of a number of online measurements; Bruce Lindbloom's is reliable and he's got calculators and spreadsheets out the yin-yang to put the data into any format you can dream of. Second, regardless of the condition of your ColorChecker, you can (and should) use those spectrophotometer measurements for profiling instead of whatever generic values you're currently using. It's proven to be a remarkably reliable tool over the years, but there _is_ variation from batch to batch (even if minimal). I'll close by noting that 24 patches is nowhere near enough for critical work. The Passport is far superior to the classic in all respects, and the ultimate field tool for normalizing white balance and exposure. But for critical studio work, especially reprographic work, even it's not really up to the task. For that, you should either plan on spending many hundreds on a not-bad chart or many hours in making your own really, really good chart. No particular skill is required; just a fair amount of mindless work. Cheers, b&