Using Gray Card to correct image color balance

G
Posted By
Greg
Dec 11, 2008
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527
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4
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Closed
Using a Canon dslr and CS2; I frequently take a close shot of a gray card to aid in balancing subsequent images taken immediately following the gray card shot, and then in Photoshop I have the gray card image on the monitor along with an image I want to balance.

Till now I have selected a small part of the gray card and dragged it onto the image, flattened the layers and used the gray eyedropper in Curves to correct the gray card portion to neutral gray, which of course corrects the image as well.

Subsequently I crop off the gray card portion, but sometimes when I do not want to crop the image, I cannot put a gray card area onto the image. I suppose I could increase the canvas size and put the gray card segment there, and crop it off later

Looking at the ‘Match Color’ control caused me to wonder if there is any way to correct the gray card and have the image follow suit, without actually having to transplant part of the gray card onto the image and then crop it off again. This ability would considerably speed up processing a number of images if it can be done.

Colin D.

How to Master Sharpening in Photoshop

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MR
Mike Russell
Dec 11, 2008
On Fri, 12 Dec 2008 00:20:51 +1300, Colin.D wrote:

Using a Canon dslr and CS2; I frequently take a close shot of a gray card to aid in balancing subsequent images taken immediately following the gray card shot, and then in Photoshop I have the gray card image on the monitor along with an image I want to balance.

Till now I have selected a small part of the gray card and dragged it onto the image, flattened the layers and used the gray eyedropper in Curves to correct the gray card portion to neutral gray, which of course corrects the image as well.

Subsequently I crop off the gray card portion, but sometimes when I do not want to crop the image, I cannot put a gray card area onto the image. I suppose I could increase the canvas size and put the gray card segment there, and crop it off later

Looking at the ‘Match Color’ control caused me to wonder if there is any way to correct the gray card and have the image follow suit, without actually having to transplant part of the gray card onto the image and then crop it off again. This ability would considerably speed up processing a number of images if it can be done.

Hi Colin,

Try this: use a curves adjustment layer on your gray card image, then drag the adjustment layer onto your other images.

BTW – there are limitations to using the gray eyedropper. You may have noticed, for example, that it does not correct a color cast in the highlights to the same extent that it does in the mid-tones. There are ways to deal with this.

Mike Russell – http://www.curvemeister.com
G
Greg
Dec 12, 2008
Mike Russell wrote:
On Fri, 12 Dec 2008 00:20:51 +1300, Colin.D wrote:

Using a Canon dslr and CS2; I frequently take a close shot of a gray card to aid in balancing subsequent images taken immediately following the gray card shot, and then in Photoshop I have the gray card image on the monitor along with an image I want to balance.

Till now I have selected a small part of the gray card and dragged it onto the image, flattened the layers and used the gray eyedropper in Curves to correct the gray card portion to neutral gray, which of course corrects the image as well.

Subsequently I crop off the gray card portion, but sometimes when I do not want to crop the image, I cannot put a gray card area onto the image. I suppose I could increase the canvas size and put the gray card segment there, and crop it off later

Looking at the ‘Match Color’ control caused me to wonder if there is any way to correct the gray card and have the image follow suit, without actually having to transplant part of the gray card onto the image and then crop it off again. This ability would considerably speed up processing a number of images if it can be done.

Hi Colin,

Try this: use a curves adjustment layer on your gray card image, then drag the adjustment layer onto your other images.

BTW – there are limitations to using the gray eyedropper. You may have noticed, for example, that it does not correct a color cast in the highlights to the same extent that it does in the mid-tones. There are ways to deal with this.

Hello Mike,

Thanks very much for the info – I had completely forgotten about being able to save correction curves in Curves, and it worked very well. Thanks again.

I don’t really like using auto WB, as it can be different for each shot, so I generally use a fixed WB – sunlight, cloudy, whatever, shoot a gray card, and use the correction to fix the subsequent shots. It may not be the absolute last word, but it’s pretty close, before doing detailed work like shading and lightening various parts of the image.

Regards,

Colin D.
MR
Mike Russell
Dec 12, 2008
On Fri, 12 Dec 2008 20:10:30 +1300, Colin.D wrote:

I don’t really like using auto WB, as it can be different for each shot, so I generally use a fixed WB – sunlight, cloudy, whatever, shoot a gray card, and use the correction to fix the subsequent shots. It may not be the absolute last word, but it’s pretty close, before doing detailed work like shading and lightening various parts of the image.

Colin,

You’ve obviously put quite some original thinking into your methods.

I would propose that you try a small addition to your current procedure. After clicking the gray eyedropper, move the ends of each of the RGB curves to make the curves more straight – see if you think the look is an improvement. The idea is to propagate the effect of the gray eyedropper to reduce any color cast in the highlights.

Mike Russell – http://www.curvemeister.com
J
jaSPAMc
Dec 12, 2008
Mike Russell found these unused words:

On Fri, 12 Dec 2008 20:10:30 +1300, Colin.D wrote:

I don’t really like using auto WB, as it can be different for each shot, so I generally use a fixed WB – sunlight, cloudy, whatever, shoot a gray card, and use the correction to fix the subsequent shots. It may not be the absolute last word, but it’s pretty close, before doing detailed work like shading and lightening various parts of the image.

Colin,

You’ve obviously put quite some original thinking into your methods.
I would propose that you try a small addition to your current procedure. After clicking the gray eyedropper, move the ends of each of the RGB curves to make the curves more straight – see if you think the look is an improvement. The idea is to propagate the effect of the gray eyedropper to reduce any color cast in the highlights.

Epson’s TWAIN ‘;tool’ allows you to correct a ‘white’ highlight to ‘pure’ white. You’d see the shift of the three colours to ‘make the balance. It will affect the mid tones, so a grey balance is a second step.

How to Master Sharpening in Photoshop

Give your photos a professional finish with sharpening in Photoshop. Learn to enhance details, create contrast, and prepare your images for print, web, and social media.

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