I may be jumping into the middle of a conversation I don't understand..... but....

Why would you (If you do) assume the photographed MacBeth chart would include an absolute white and black? All of the (6 on mine) grayscale steps should be non clipped and reasonable nuetral in a well exposed and well white balanced capture/file. But, the black should NOT be "0,0,0" and the white should NOT be "255,255,255".

Something LIKE (not exact) "10,10,10" for black and "245,245,245" for the white would indicate a good color balance and exposure/contrast.

There are things to be photographed brighter than white paper! The relection in water or metal of the lightsource (as an example). There are things darker than black paper to be photographed, just look into deep shadows.

The darker of the two middle grays (on mine) is close to 18%. I'm NOT sure it is meant to be exactly 18%.

Older MacBeth charts came with LAB values for each patch, you can convert them to RGB here:
http://www.colorpro.com/info/tools/convert.htm

Newer ones include RGB values (or so my friend bragged).

Hope that helped. Hope I haven't confused things or miss-understood.

In article <UzjFb.18381$>, Linda Gregory
wrote:

I just want to correct the patches. For example, the white to black patches are not accurate

because the white is not white and the black is dark grey. Also, what
grey

patch is 18% grey?

Are you sure THEY'RE not right and your monitor/printer wrong?
That's the idea behind their posting it, to show you the correct colors/contrast and you adjust your equipment to match. If you only print on your computer/printer set up and do not take it elsewhere, then you're fine, but you need to calibrate to match the Greytag/Macbeth so you can take your work elsewhere.

Linda

Tom Ferguson

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MACBETH Color Chart RGB Values