Neutral Balance Sample Size.

[Dinarius]

While most RAW image processors offer 5x5 as the typical sample size for the white/grey neutralization picker, CS3 offers sample sizes up to 100+.

If you process in, say, ACR4 or Flexcolor (as I do) and open a Levels adjustment layer in CS3 and hold the grey picker over the grey card (or whatever you use) the difference in the readings is radical, to say the least.

Indeed, if you take a sample at, say, 101x101, your image will alter considerably.

I'm usually in a situation where I'm relying very heavily on a combination of grey card (the excellent basICColor card, in my case) and a Gretag Macbeth Color Checker, since a lot of what I do is on location and colour critical (fine art documentation for catalogues).

I guess that the colour temp reading after a grey sample is the most telling indication of the correct sample size. Or is it?

Do others use the standard small size or use Photoshops larger options?

D.

[madmanchan]

Camera Raw's white balance picker is not fixed in size; it depends on what zoom level you're on. So if you want CR to average more pixels, zoom out and then do click-WB.

That said, if you're seeing lots of variation, then it means your image is probably noisy. Try shooting your CC / gray chart images at the lowest possible ISO and out of focus as well, to prevent surface imperfections from screwing up the click-WB process.

[Dinarius]

Try shooting your CC / gray chart images at the lowest possible ISO and out of focus as well, to prevent surface imperfections from screwing up the click-WB process.
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Interesting suggestion about shooting out of focus.

I shoot everything at 100 ISO.

Most of my work is on a H3D39Mp with strobe. Noise isn't usually a problem.

Thanks.

D.

[Raw shooter]

Camera Raw's white balance picker is not fixed in size; it depends on what zoom level you're on. So if you want CR to average more pixels, zoom out and then do click-WB.
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I wonder if the new ACR 5.x (CS4) does offer an enlargable sample option (right click?) for White Balance.  I'm with the OP on this one - as my work is also based on proper and accurate WB.  This would make for a great upgrade for many.

[madmanchan]

I'm confused as to what the issue is. If you shoot the CC 24 a little out of focus (to hide surface imperfections) at low ISO and you really have minimal noise, then it should not matter how many samples you use, nor where you click within the patch, in terms of what the WB is. It should be spot-on perfect. You can even be zoomed in to 400% or zoomed out to 25% and get the same results. You could then open the image in PS and manually check every pixel to make sure they have equal RGB components (should be within a single 8-bit level).

(BTW my recommendation is to use the 2nd patch from the left in the 4th row, not the 1st (white) patch.)