I have gone through the online ACR4 HELP and if anything is written there about the Color Sampler Tool and, in particular, how many pixels it samples (e.g. 1 x 1, 5 x 5 or whatever), I can't find it!
So, what's the answer?
Secondly, in my work, I use Gretag Color Checker in just about every shot, in addition to a basICColor Grey Card. I am very careful about keeping them clean and where on the patches/card I sample from.
However, I have noticed the following:
Having sampled in ACR and the converted, when an image is opened in CS3 the 1 x 1 and 5 x 5 samples are exactly as in ACR, leading me to believe that ACR samples one of these sample sizes. But, if I increase the sample size in CS3 (this now offers four larger sample sizes) the reading get progressively worse.
I would have thought that a 31 x 31 sample from a grey card would be far more accurate than a 1 x 1 or 5 x 5? Why are they worse? Should I be resampling my CC or grey card in CS3 using a larger number of pixels?
What really concerns me is that I use the (brilliant!) HSL panel in ACR4 to correct the RGBY patches and the Grey card so that they are correct. But, when I then convert, the values are only correct in CS3 up to 11 x 11 and not above.
Why is this?
Finally, it would be good to allow the Color Sampler Tool in ACR to make much larger samples. At the very least, it should be possible to select the same 7 options available in CS3. And it should be possible to sample in % (as in Lightroom) AND(!) Lab.