Cast removal in small areas

No.
See my tip on removing the bluish cast in shadows taken under open sky for one technique. It would work for any color cast problems.

wrote:

After editing a complete image, there are a few small areas left that have unwanted casts in them. Without making a selection, are there ways to turn these areas into neutral? Thanks.

—
Robert D Feinman

Landscapes, Cityscapes, Panoramic Photographs: http://robertdfeinman.com

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After editing a complete image, there are a few small areas left that have unwanted casts in them. Without making a selection, are there ways to turn these areas into neutral? Thanks.

It depends on how the color variation within these small areas overlaps with the color variation in the rest of the image. If you’re lucky, you might be able to use curves, HSB, blending, etc. By far the best reference for this sort of thing is Dan Margulis’s book, Professional Photoshop.

wrote:

After editing a complete image, there are a few small areas left that have unwanted casts in them. Without making a selection, are there ways to turn these areas into neutral? Thanks.

It is certainly possible, and is done all the time.

For example, in Lab mode you may be able to zero out the color and reduce or eliminate the cast.

You may be able to convert to CMYK mode, with a heavy or max GCR setting, remove the particular cast, and then convert back to RGB. Or selective color might get the job done.

Although you specified no use of masks, which is good. Another related approach, similar to masking, would be to dup the layer, correct only areas affected by the color cast, and then use the layer blending options to select only part of the image.

At the end of the day, there are some mixed lighting situations that may require masking, though the mask may be derived from the image, for example by sharply curving the a or b channel, rather than created by hand.

We love a challenge, why not post your image and see if anyone takes a crack at fixing it?

—

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Warren Sarle wrote:

wrote in message

After editing a complete image, there are a few small areas left that have unwanted casts in them. Without making a selection, are there ways to turn these areas into neutral? Thanks.

It depends on how the color variation within these small areas overlaps with the color variation in the rest of the image. If you’re lucky, you might be able to use curves, HSB, blending, etc. By far the best reference for this sort of thing is Dan Margulis’s book, Professional Photoshop.

The color variation within these small areas do overlap with the color variation in the rest of the image. Without making a selection, I can’t remove the cast without also influencing the rest of the image. Margulis’ book is very helpful in many situations, and I reference it often. However, without a more detailed step by step tutorial, I find his suggestions on how to use curves and blending rather difficult to apply in some situations and at my level.

For example. He chooses and edits the black channel as the blending source for a lemon. But the black channel is hardly the obvious choice at first sight. How did he make that choice?

I also have difficulties with images that should end up with no neutral white or black points, or with a certain cast. How do I maximize the highlights and shadows without pushing them to neutrals?

I’ll see if I can post an example as suggested by Mike.

Mike Russell wrote:

wrote:

After editing a complete image, there are a few small areas left that have unwanted casts in them. Without making a selection, are there ways to turn these areas into neutral? Thanks.

It is certainly possible, and is done all the time.

For example, in Lab mode you may be able to zero out the color and reduce or eliminate the cast.

You may be able to convert to CMYK mode, with a heavy or max GCR setting, remove the particular cast, and then convert back to RGB. Or selective color might get the job done.

Although you specified no use of masks, which is good. Another related approach, similar to masking, would be to dup the layer, correct only areas affected by the color cast, and then use the layer blending options to select only part of the image.

Can I do this blending without making a selection?

At the end of the day, there are some mixed lighting situations that may require masking, though the mask may be derived from the image, for example by sharply curving the a or b channel, rather than created by hand.

I’m OK when making selections that are rather distinct, but shaky with those with a more murky edges.

We love a challenge, why not post your image and see if anyone takes a crack at fixing it?

See my response to Warren. I’ll see if I can post an example. TIA.

Mike Russell wrote:

[re removing a cast from part of an image]

Although you specified no use of masks, which is good. Another related approach, similar to masking, would be to dup the layer, correct only areas affected by the color cast, and then use the layer blending options to select only part of the image.

wrote:

Can I do this blending without making a selection?

yes – double click on the layer name in the layers palette and there will be sliders that allow you to determine when the upper layer preempts the lower layer.

You are right on track, though, in trying to do this without using a selection, and I would not resort to layer blending until you had already tried normal curve manipulations.

—

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

wrote in message

Mike Russell wrote:

We love a challenge, why not post your image and see if anyone takes a

crack

at fixing it?

My first time posting images here. Hope they show.

Mike should have said, "post your image on your web site, or in an alt.binaries.* newsgroup." People who have to pay according to the size of stuff they download don’t appreciate such large posts.

I take it the main thing you are trying to do is make the background cyan, to contrast with all parts of the flowers. There are, of course, many ways to do this. Perhaps the simplest would be to lower the shadow part of the curve for the red channel. You can do this without altering the flowers by putting 3 or 4 knots in the middle of the red curve to nail it down. This gives you a dark cyan background.

A more flexible way would be to select the background using the red channel, which has good contrast between the background and the flowers. Open the channels palette and duplicate the red channel. Click on the red copy, then use curves to increase the contrast until the flowers are solid white and the background is very dark (it does’t have to be solid black). Then go to the selection menu, choose "Load Selection", and load the red copy, inverted. This gave me a good selection when I did it on your raw image. The little green branch might be a problem, in which case you use a different channel to select the branch and subtract that from the selection of the background.

Once you have the background selected, I would say the easiest way to change it to cyan would be an adjustment layer using color balance.

wrote in message

After editing a complete image, there are a few small areas left that have unwanted casts in them. Without making a selection, are there ways to turn these areas into neutral? Thanks.

Sponge tool set to Desaturate.