MACBETH Color Chart RGB Values

I would like to fine tune a Macbeth color chart I got on the internet with Photoshop 5.0 ELements. I got the RGB values for each patch no. Can anyone advise me on how to modify each patch that I have to the correct patch. For example, my patch no 18 reads RGB 0, 134, 169 and the correct is 0, 148, 189. How do change mine to the correct RB values?
Do I go to hue saturation and do trial and error?
Is there any place I can type in the correct values and have the patch turn out correct.
Can I make my own chart by typing in the correct values and have Photoshop make the colors?
Thanks for any advice on this, Rick

On 19 Dec 2003 07:59:55 GMT, (Stromer2) wrote:

I would like to fine tune a Macbeth color chart I got on the internet with Photoshop 5.0 ELements. I got the RGB values for each patch no. Can anyone advise me on how to modify each patch that I have to the correct patch. For example, my patch no 18 reads RGB 0, 134, 169 and the correct is 0, 148, 189. How do change mine to the correct RB values?
Do I go to hue saturation and do trial and error?
Is there any place I can type in the correct values and have the patch turn out correct.
Can I make my own chart by typing in the correct values and have Photoshop make the colors?
Thanks for any advice on this, Rick

Rick, I hope you get some good answers for this. What model Macbeth unit are you using? Is this like a pressroom color density unit (reflection densitometer) used for determining dot gain and color densities? It would be nice to know what the process is for creating an ink/paper ICC profile through the use of a spot color densitometer. Too bad these Macbeth color charts are so expensive ($80), they'd also be of value in checking for color shift in digital cameras/lenses.

I don't know what Model it is. I got it of the internet. 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?
Another reply gave me a link to a site that shows many different versions - different RGB values for each patch.
Thanks for the reply, Rick

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

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