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Author Topic: Remove blue cast  (Read 13508 times)
sunmoonlake
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« on: May 07, 2008, 02:25:35 PM »
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Hi all,

I recently shot some waterfalls and tree lines in oregon. Most days were rainy and overcast, plus lots of cast from tall trees overhead. I shot with Provia 100F and sometimes long exposure (10-25sec) and sometimes with ND & polarizer filters combined. The problem I saw in some of my photos are the blue cast that is definitely not intended. What can I do to remove the blue cast in PS? What should I do next time to fix the problem in camera?


Your response is much appreciated.
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DarkPenguin
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« Reply #1 on: May 07, 2008, 02:35:44 PM »
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Sample image?
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sunmoonlake
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« Reply #2 on: May 07, 2008, 04:12:01 PM »
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I will re-post the question after I get the films scanned. But, in the meanwhile, if anyone presumably know the issue I am talking about. Your input is much appreciated.

Thanks for the reminder.
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Dale_Cotton
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« Reply #3 on: May 07, 2008, 04:21:48 PM »
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Curves, blue channel, drag line down.
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DiaAzul
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« Reply #4 on: May 07, 2008, 06:01:58 PM »
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I will re-post the question after I get the films scanned. But, in the meanwhile, if anyone presumably know the issue I am talking about. Your input is much appreciated.

Thanks for the reminder.
[a href=\"index.php?act=findpost&pid=194237\"][{POST_SNAPBACK}][/a]

The best tool for removing colour cast in an image is the colour balance tool/adjustment layer in conjunction with the colour palette (or color if you are using a US version of PS).

To remove colour cast - make sure that you can see the colour palette (this has three sliders for Red, Green, Blue. Add a colour balance layer.

Select highlights in the colour balance adjustment layer radio button. Click on a known neutral highlight. The sliders in the colour palette will show the RGB values of the selected point (e.g. 246, 234, 228). Move the sliders in the adjustment layer to make the numbers equal (e.g. 240,240,240). Repeat for shadows and midtones (NB remember to select a neutral shadow and midtone in the image before making adjustments).

If there aren't any neutral points in the image then you will need to use best judgement.

The resulting image should now have any colour cast neutralised. (NB if there are multiple light sources then you can use the same technique but mask different areas depending upon which light falls on them).
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David Plummer    http://photo.tanzo.org/
Geoff Wittig
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« Reply #5 on: May 07, 2008, 08:20:23 PM »
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The best tool for removing colour cast in an image is the colour balance tool/adjustment layer in conjunction with the colour palette (or color if you are using a US version of PS).

To remove colour cast - make sure that you can see the colour palette (this has three sliders for Red, Green, Blue. Add a colour balance layer.

Select highlights in the colour balance adjustment layer radio button. Click on a known neutral highlight. The sliders in the colour palette will show the RGB values of the selected point (e.g. 246, 234, 228). Move the sliders in the adjustment layer to make the numbers equal (e.g. 240,240,240). Repeat for shadows and midtones (NB remember to select a neutral shadow and midtone in the image before making adjustments).

If there aren't any neutral points in the image then you will need to use best judgement.

The resulting image should now have any colour cast neutralised. (NB if there are multiple light sources then you can use the same technique but mask different areas depending upon which light falls on them).
[a href=\"index.php?act=findpost&pid=194256\"][{POST_SNAPBACK}][/a]

Or, you can simply create a curves adjustment layer, and use the eyedropper tool to get a neutral color balance. You can use the mid-tone eyedropper and search for a neutral grey in the image if you have some grey rocks. Or, you can use the highlight eyedropper and click on the water to get a clean neutral white. You can also adjust the resulting curves to taste.
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Dale Allyn
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« Reply #6 on: May 07, 2008, 09:33:20 PM »
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Here's a pretty good tutorial by Scott Kelby that describes much of what Geoff suggested above: http://www.macworld.com/article/132982/200...2505.html?t=103

It was published in MacWorld, but it's an excerpt from Scott's book and applies equally to the use of Photoshop on the Mac or Windows platform.

Good luck.
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gdanmitchell
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« Reply #7 on: May 11, 2008, 02:37:28 PM »
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Hi all,

I recently shot some waterfalls and tree lines in oregon. Most days were rainy and overcast, plus lots of cast from tall trees overhead. I shot with Provia 100F and sometimes long exposure (10-25sec) and sometimes with ND & polarizer filters combined. The problem I saw in some of my photos are the blue cast that is definitely not intended. What can I do to remove the blue cast in PS? What should I do next time to fix the problem in camera?
Your response is much appreciated.
[a href=\"index.php?act=findpost&pid=194213\"][{POST_SNAPBACK}][/a]

I do some sort of selection around the waterfall - there are various ways to do this. I can often fix this issue sufficiently if I simply desaturate the waterfall itself a bit. I may also play with levels/curves a bit to bring up the overall brightness and it is possible that some color correction may also be needed.

It can be tricky to find just the right balance between "weirdly blue" and "phony white" - so you'll likely have to play with it a bit. If the whole image in largely in shade, warming up the whole thing might be part of the process, too.
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G Dan Mitchell
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« Reply #8 on: May 11, 2008, 07:44:39 PM »
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I find that Provia is susceptible to making anything in shadow too blue. I correct the situation by bringing a color temperature meter with me and some correcting filters  I carry 81A to 81EF  and 85A-85C.  I also find that I have to use these filters at altitude and in overcast conditions to correct the color temperature.
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sunmoonlake
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« Reply #9 on: May 13, 2008, 04:13:29 PM »
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Thanks everyone!!! All of your replies have tremendously helped.
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walter.sk
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« Reply #10 on: May 14, 2008, 09:33:10 AM »
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Thanks everyone!!! All of your replies have tremendously helped.
[a href=\"index.php?act=findpost&pid=195566\"][{POST_SNAPBACK}][/a]
If you have scanned the image into the computer, one really easy way to change the blue caste is to make a rough selection around the waterfall.  Open a Curves Adjustment Layer and on the dropdown menu select Blue rather than the default RGB.  Ctrl-Click on the area that is too blue, and you will get a point placed on the curve.  Use the Down Arrow to pull that point down until most or all of the blue is gone.

Another quicky:  Make the rough selection around the waterfall.Make a Selective Color Adjustment Layer.  On the dropdown menu select Whites.  One slider controls Blue/Yellow.  Add a bit of yellow.
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gdanmitchell
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« Reply #11 on: May 14, 2008, 02:13:59 PM »
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Replying to my own post... my apologies for overlooking the fact that you shot film rather than digital. In that context my reply was perhaps completely unhelpful, unless you scan the film  and process digitally.

Dan

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I do some sort of selection around the waterfall - there are various ways to do this. I can often fix this issue sufficiently if I simply desaturate the waterfall itself a bit. I may also play with levels/curves a bit to bring up the overall brightness and it is possible that some color correction may also be needed.

It can be tricky to find just the right balance between "weirdly blue" and "phony white" - so you'll likely have to play with it a bit. If the whole image in largely in shade, warming up the whole thing might be part of the process, too.
[a href=\"index.php?act=findpost&pid=195076\"][{POST_SNAPBACK}][/a]
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G Dan Mitchell
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« Reply #12 on: May 15, 2008, 12:40:31 AM »
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One trick I've used to do rough color corrections on my 4x5 film scans has been using a Color Fill Layer set to color blending mode, controlled with the opacity slider.

Choose new fill layer, set the blending mode to Color.

Pick the opposite color of your cast (helps to know basic color theory here - blue vs yellow, green vs magenta, red vs cyan and whatnot).

Use the opacity slider of your new layer to control how strong the effect is. I find that 10-20% opacity will normally do the trick.
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bradleygibson
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« Reply #13 on: May 15, 2008, 03:35:11 PM »
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Hi all,

I recently shot some waterfalls and tree lines in oregon. Most days were rainy and overcast, plus lots of cast from tall trees overhead. I shot with Provia 100F and sometimes long exposure (10-25sec) and sometimes with ND & polarizer filters combined. The problem I saw in some of my photos are the blue cast that is definitely not intended. What can I do to remove the blue cast in PS? What should I do next time to fix the problem in camera?
Your response is much appreciated.
[a href=\"index.php?act=findpost&pid=194213\"][{POST_SNAPBACK}][/a]

I have read explanations of why shadows often have a blue cast, and for the life of me I can't remember why.  

In any case, the solutions proposed that balance the entire image to the cast of the shadow might not be what you want, particularly if you like the colors in the non-shadow areas of your image.

You have another option of selecting just the shadows in your image and either desaturating them somewhat (for a natural look), cancelling some of the blue cast with a hue shift, or both.

An inverted density selection (CTRL+SHIFT+ALT+~ in PSCS3 followed by CTRL+SHIFT+I to invert the selection) will let you isolate the shadows, followed by an HSV adjustment layer will give you superb control and ability to knock out the shadow cast in a very subtle, natural way.

-Brad
« Last Edit: May 15, 2008, 03:36:38 PM by bradleygibson » Logged

etrump
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« Reply #14 on: May 16, 2008, 12:24:25 AM »
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Why not just use photoshop warming filter to warm things up and remove the blue cast or open it in camera raw and tweak white balance there?
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Ed Cooley

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DiaAzul
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« Reply #15 on: May 16, 2008, 02:55:13 AM »
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I have read explanations of why shadows often have a blue cast, and for the life of me I can't remember why. 


[a href=\"index.php?act=findpost&pid=195979\"][{POST_SNAPBACK}][/a]

On a bright and sunny day there are two light sources - a specular light source (the sun) and a very broad light source (blue sky/ refracted light). The sky provides fill light in the shadows, hence, the blue tint.
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David Plummer    http://photo.tanzo.org/
KevinA
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« Reply #16 on: May 17, 2008, 03:12:13 AM »
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Hi all,

I recently shot some waterfalls and tree lines in oregon. Most days were rainy and overcast, plus lots of cast from tall trees overhead. I shot with Provia 100F and sometimes long exposure (10-25sec) and sometimes with ND & polarizer filters combined. The problem I saw in some of my photos are the blue cast that is definitely not intended. What can I do to remove the blue cast in PS? What should I do next time to fix the problem in camera?
Your response is much appreciated.
[a href=\"index.php?act=findpost&pid=194213\"][{POST_SNAPBACK}][/a]

This all sounds a bit arse about face  to me, as you shot it on Provia I assume you are scanning it. You are better getting the scan as you like it rather than Photoshopping it after the event.
As for correcting when shooting a slight warming filter would help, this will add a general warmth to the image, although you could do that as I said in the scanning, the less you need to do in Photoshop the better. If it's a localised colour cast you could make two scans, one neutral one warm and combine the two in photoshop and gentle erase part of one of the layers to reveal the one underneath. This would be better than tweaking curves and levels.

Kevin.
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Kevin.
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