Levels Eyedroppers for Removing Color Cast

PA
Posted By
pixel_a_ted
Oct 18, 2010
Views
2002
Replies
6
Status
Closed
Photographers use a grey card to remove a color cast from an image. You click on the grey card with the midtone Levels eyedropper to set the grey point, the grey card becomes the neutral grey that it should be and the rest of the image is "fixed." It appears that the adjustments extend all the way into the highlight regions.

If you then use the highlight eyedropper to set the white point, doesn’t it in some sense undo or conflict with what the midtone eyedropper did? If it’s valid to use all three eyedroppers for a given image, is there a preferred order for using them?

Thanks.
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color level remove

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J
jaSPAMc
Oct 19, 2010
pixel_a_ted found these unused words:

Photographers use a grey card to remove a color cast from an image. You click on the grey card with the midtone Levels eyedropper to set the grey point, the grey card becomes the neutral grey that it should be and the rest of the image is "fixed." It appears that the adjustments extend all the way into the highlight regions.
If you then use the highlight eyedropper to set the white point, doesn’t it in some sense undo or conflict with what the midtone eyedropper did? If it’s valid to use all three eyedroppers for a given image, is there a preferred order for using them?

Thanks.
For me … Black, White, Grey.

Image archivists usually include a step grey card against the scan.
TC
tony cooper
Oct 19, 2010
On Tue, 19 Oct 2010 09:14:38 -0700, Sir F. A. Rien
wrote:

pixel_a_ted found these unused words:

Photographers use a grey card to remove a color cast from an image. You click on the grey card with the midtone Levels eyedropper to set the grey point, the grey card becomes the neutral grey that it should be and the rest of the image is "fixed." It appears that the adjustments extend all the way into the highlight regions.
If you then use the highlight eyedropper to set the white point, doesn’t it in some sense undo or conflict with what the midtone eyedropper did? If it’s valid to use all three eyedroppers for a given image, is there a preferred order for using them?

Thanks.
For me … Black, White, Grey.

Image archivists usually include a step grey card against the scan.

For me… White, Black, Grey. I don’t think it makes any difference, though. I’d be interested to know if it does.

—
Tony Cooper – Orlando, Florida
D
DrJohnRuss
Oct 20, 2010
On Oct 19, 12:54 pm, tony cooper wrote:
On Tue, 19 Oct 2010 09:14:38 -0700, Sir F. A. Rien

wrote:
pixel_a_ted found these unused words:

Photographers use a grey card to remove a color cast from an image. You click on the grey card with the midtone Levels eyedropper to set the grey point, the grey card becomes the neutral grey that it should be and the rest of the image is "fixed." It appears that the adjustments extend all the way into the highlight regions.

If you then use the highlight eyedropper to set the white point, doesn’t it in some sense undo or conflict with what the midtone eyedropper did? If it’s valid to use all three eyedroppers for a given image, is there a preferred order for using them?

Thanks.

For me … Black, White, Grey.

Image archivists usually include a step grey card against the scan.

For me… White, Black, Grey.  I don’t think it makes any difference, though.  I’d be interested to know if it does.

—
Tony Cooper – Orlando, Florida

You can see if there is a difference by watching the graphs for the transfer function. It is usually best to do grey last.

John Russ
PA
pixel_a_ted
Oct 20, 2010
Thanks for the suggestions. I was trying to find the a sound technical rationale for using 3 eyedroppers instead of just the one midtone one (as you can use the Levels sliders to set white and black levels without the neutralizing effect of the white and black eyedropper) and my main concern was that after using one eyedropper the next one used partially undoes the effect of the first. But it is sounding like it’s a very empirical process.
PA
pixel_a_ted
Oct 20, 2010
Been doing some experimenting and it does seem doing grey last works best. Thanks.
J
jaSPAMc
Oct 21, 2010
pixel_a_ted found these unused words:

Been doing some experimenting and it does seem doing grey last works best. Thanks.
Look at the reasoning:

Setting the white level corrects all the way to ‘Black’, Correcting Blak, finished the major tonality. Grey is a ‘touch up’ from there.

Try making the corrrections with the curves tool. You’ll see the different amounts applied to each colour a you proceed.

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