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Old May 6, 2011, 7:53 PM   #1
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Default [SOLVED] Please recommend me an application/filter to remove these yellow blotches.

Hello guys. My camera produces yellow blotches when shooting under incandescent lighting and high ISOs. Here's an example:

(extreme case, ISO 1600, very low incandescent lighting (60W 3m away, litegrey walls))

I need an application or photoshop filter to remove them. Could you recommend me a good one please?

Thank you.

Last edited by Electrolyte; May 7, 2011 at 9:34 AM.
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Old May 6, 2011, 8:32 PM   #2
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I use the color replacement tool in Photoimpact, and I believe Photoshop Elements has a similar tool. Select the color which is a problem and adjust the sliders to change the hue slightly towards blue, and reduce the saturation. You will have to adjust the similarity to avoid leaving parts of the undesired color. It takes some practice.

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Old May 7, 2011, 6:13 AM   #3
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Thank you. However, if anyone knows an automatic solution (an one-click) please lemme know. I know it's possible to repair "manually" but it would take some time to analyze and adjust each image.
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Old May 7, 2011, 6:48 AM   #4
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I hope this doesn't sound flippant, but are sure it's a problem with the camera? I can only see yellow spots on the cow, nothing on the surrounding background (what there is of it) - I'm wondering if it could have been splashed with something which the camera is picking up even if you can't see it. Can you try a test shot with a fresh, clean piece of white paper and see if you get the same result?

The yellow on the bottom of then neck seems particularly strong and follows the line of the neck much more closely than I'd expect from an image artefact.

[EDIT] Or alternatively, take another photo of the cow from a slightly different angle and see if the blotches are in the same place,

I also tried Topaz Denoise with the 'Clean Color' set to maximum which did clear most of the yellow blotches up automatically but it's not free software.
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Old May 7, 2011, 7:44 AM   #5
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This is fairly common with higher ISO settings in low incandescent light. Parts of the picture have essentially no blue component, and between the jpeg compression and the camera's denoise algorithms, you get left with the yellow blotches.
Hadn't thought about the Topaz denoise, but will give it a try with a couple of my pics.

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Old May 7, 2011, 8:35 AM   #6
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Quote:
Originally Posted by MartinSykes View Post
I hope this doesn't sound flippant, but are sure it's a problem with the camera? I can only see yellow spots on the cow, nothing on the surrounding background (what there is of it) - I'm wondering if it could have been splashed with something which the camera is picking up even if you can't see it. Can you try a test shot with a fresh, clean piece of white paper and see if you get the same result?

The yellow on the bottom of then neck seems particularly strong and follows the line of the neck much more closely than I'd expect from an image artefact.

[EDIT] Or alternatively, take another photo of the cow from a slightly different angle and see if the blotches are in the same place,

I also tried Topaz Denoise with the 'Clean Color' set to maximum which did clear most of the yellow blotches up automatically but it's not free software.
Originally I took a bunch of photos to make sure the problem was the camera, and looking them in sequence is possible to notice very clearly that the blotches appears randomly. Even taking the picture from almost the same angle.
Thanks for the software recommendation it's somewhat expensive, but I'm downloading the trial and if it really fix that i'll consider buying it.

The spots doesn't appear on glossy white materials, that's why the background is okay. Also, it's a little bit out of focus, what prevents the artifacts also.

Another kind of artifact that appears in similar light conditions but lower ISOs (<400) is blue blotches on dark materials. Sometimes a low yellow and blue "noise" appears on dark surfaces.

For example, I took a long-exposed picture of the sky last night (60s, ISO200) and even if it's good because it captured stars not visible for the naked eye, the sky was all stained with blue and yellow 'low noise'.

This camera has a considerable amount of high noise (pixel sized grain) which is good because it's easily and efficiently filterable automatically by any decent application, however, that kind of artifact is hard to fix.

Thanks guys.
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Old May 7, 2011, 9:31 AM   #7
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Awesome! Topaz DeNoise really removed the blotches!
It's by far the best denoise program i've ever seen. I thought noise ninja was the best but this one simply rocks. It's the first denoise program that really tried to revert the noise and artifacts instead of just smoothing it. It's incredible how the details doesn't get smoother. And the colour correction affects only the problematic area. I painted an very light yellow dot on an paper and it's almost indistinguishable from the artifacts, but Topaz did fixed the artifacts and let the painted dot intact.
It doesn't work very well for the sky because it also remove the colours of the stars, but only the denoising itself improves it by far, and using a small colour correction it's possible to achieve incredibly better results without affecting the stars too much.
In short, it's incredible. I'm definately buying it as soon the license expires.

Thank you very much Mr. Martin Sykes for recommending me such amazing piece of software!
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Old May 8, 2011, 9:23 PM   #8
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I've had a go with Photoshop Elements version 2. I enlarged the picture very considerably, then chose what looked like some especially yellow pixels, and used the 'replace color' command. A few seconds were spent changing the hue & adjusting the fuzziness control & lightening and darkening the spot till it pretty well blended in with the surroundings.

Nothing to do with those steps - but I'm curious - why, Martin S., do you describe it as a picture of a cow? I grew up on a farm and I can't for the life of me see a cow in the picture.

Anyway, here's my version -
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Old May 9, 2011, 12:03 AM   #9
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The black and white pattern says "Holstein" to me. My guess is it is a handcrafted something or other.

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Old May 9, 2011, 2:34 AM   #10
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Quote:
Originally Posted by Herb View Post
Nothing to do with those steps - but I'm curious - why, Martin S., do you describe it as a picture of a cow? I grew up on a farm and I can't for the life of me see a cow in the picture.
If you Google 'Fresian cow' (or Holstein-Fresian seems to be the US equivalent) which is the most common variety here in the UK you'll see what I mean. It looks like the body of a Fresian with the head cropped off the right and the feet cropped off the bottom. Maybe Electrolyte could post a full version to see if I'm right or not...
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