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Remove Colour Cast Using channels

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Old 09-07-2005, 08:13 PM
huxley huxley is offline
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Remove Colour Cast Using channels

How would I use channels to replace the blueish cast from the wheel set
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File Type: jpg OLD CABOOSE ARCH BAR TRUCK rif.jpg (49.5 KB, 73 views)
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Old 09-08-2005, 11:08 AM
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creeduk creeduk is offline
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I wouldn't it takes a lot of platying because the problem here is in the cyan and green. Use hue and saturation to sort the blue tint.
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Old 09-08-2005, 11:35 AM
Ken Fournelle Ken Fournelle is offline
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Try a Selective Color Adjustment layer

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Old 09-08-2005, 01:13 PM
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Duv Duv is offline
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Perhaps another thought is to leave the blue alone and increase the red. This would bring it closer to medium grey and at the same time increase the rust color in the wheels.

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File Type: jpg D-Caboose.jpg (87.9 KB, 37 views)

Last edited by Duv; 09-08-2005 at 01:22 PM.
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Old 09-08-2005, 02:11 PM
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Craig Walters Craig Walters is offline
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excellent, duv!

and welcome to RP, huxley!

you could probably also use a curves adjustment layer and do pretty much the same thing that duv did using that.

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Old 09-08-2005, 03:42 PM
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philbach philbach is offline
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Cast Removal

Using Photoshop CS2 I just used adjustments auto-color and that removed a lot of the blue cast. Another easy way is to use Adjustment/Variations. The reason I like to use that is that you can see the results of adjusting hues before you make any changes.
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Old 09-08-2005, 04:19 PM
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Flora Flora is offline
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Hi huxley,

Welcome to RP!

If you want to use the channels to remove the cyan/blueish cast from your picture, here is a way of doing it:

* In the channels palette, activate the Red Channel (the one needing correction here since the cast is cyan)

TIP: to acces the composite view while working on a single Channel, just press the ~ key after activating the Channel ...

* Go to Image>apply Image (Attachment 1):

Source Channel = Green
Target Channel = Red (automatically since it's the channel you are working on ...)
Blending = Screen
Opacity = 100%
Check the 'Mask' box keeping the default Options.

If necessary, apply some further selective corrections using either Hue&Saturation, or Curves, or Levels or Selective Colors

Working with PS CS2 I used a Shadow/Highlight Adjustment to decrease the highlights and, finally, I used USM to lightly sharpen the image... (Attachment 2)
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File Type: jpg Apply_Image.jpg (83.0 KB, 39 views)
File Type: jpg F_TRUCK-rif.jpg (99.6 KB, 50 views)
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Old 09-08-2005, 05:51 PM
leuallen leuallen is offline
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Try this, although it does not use channels.

Make a duplicate. Change dup to lab mode. Eyedropper tool, select a mid to deep blue on the box cover of the left wheel. Double click, foreground color to get Color Picker. Invert the signs of the lab a and b channel, if pos make neg, neg make pos. This gives you the "opposite" color of the blue, the color that when blended will produce gray. I assumed the area I picked was near gray.

Back to the original copy. Make a new layer with blending overlay. Fill the layer with the color from the dup. Adjust opacity some if necessary. I use about 55%

Discard dup image. You might be able to eliminate the dup image by just selecting color on original image and inverting signs in the Color Picker but that is not the way I learned it. There might be a subtle difference because of lab mode.

This gets close to eliminating the cast if you picked a good gray area. I might try a couple of different color selections, and pick the best. Then adjust color if required.

Without seeing more of the picture to make judgement from, it is difficult to tell whose color is more correct. You do realize that these shadow areas are inherently blue because of the sky. It might not be wise to to reduce them too much or you may get an unnatural look.

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File Type: jpg D-Caboose-LL.jpg (92.9 KB, 27 views)
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Old 09-08-2005, 06:15 PM
Ken Fournelle Ken Fournelle is offline
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Apply Image Techniques


This is the third problem in a week in which you have used Apply Image to correct an image. I am not complaining; I find it fascinating, but where are you getting this all from? It's been great!

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Old 09-08-2005, 07:27 PM
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CJ Swartz CJ Swartz is offline
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Ken, here's a tutorial for using Apply Image to eliminate redeye -

Apply Image is used a good deal when trying to mask difficult elements in an image -- like hair

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