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Category: New Questions

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Photography Question 
Deonne 

member since: 10/2/2001
 

How to Stop Colour Cast?


Hi, everyone. I use a D100 (I'm new to digital photography) in a home studio, and I'm having problems with a pink colour cast. I am using multi blitz strobes, and the walls of the studio are white. I've tried altering the exposure levels, the white balance, and flash modes - all to no avail. I can correct this overall pink cast using Photoshop, but I would really like to get it right without having to alter everything! Any help you can offer would be greatly appreciated. Thanks!

5/12/2004 5:39:49 AM

 
Gregory LaGrange
BetterPhoto Member
gregorylagrange.org

member since: 11/11/2003
  Try changing your white balance. Your manual should explain it. You may have a feature to set a custom white balance, by taking a picture of something white with the lights you're using, and then using that picture to set the white balance - so that under that lighting, the whites will come out white.

5/12/2004 10:11:36 AM

 
Deonne 

member since: 10/2/2001
  Hi, Gregory, thanks very much for your help. I played around with the white balance more after getting your tip, and managed to get the whites looking the way they should. The skin tones are still a bit pink - any ideas on why that would be occurring? Thanks again for your help - I really appreciate it.

5/15/2004 12:16:05 AM

 
David Ziff

member since: 9/10/2003
  I'm also puzzled why this is happening. Have you checked the color temperature to be sure your studio lights aren't cooler than white light?

Whenever you have such an anomaly one tries to isolate it by excluding what it isn't with other tests.
For example, have you checked a white board in sunlight and see if you're still getting a color cast?

You can use bank A and restore the camera to default levels to ensure you haven't inadvertently tripped this cast yourself in some way you've overlooked. Does it happen in raw file? Are you getting a color cast in any other circumstances?

The manual has an in-depth analysis of white balance and image adjustment pages 50 - 62 - are you fully applying those techniques? You might also look up Thom Hogan's "Complete Guide to the Nikon D100" which is a lot more complete than the manual itself.

I hope these suggestions help. Let me know how you solve this.

David

5/18/2004 6:27:29 AM

 
Deonne 

member since: 10/2/2001
  Hi David - thanks heaps for your response, and sorry for the delayed reply! I am still having the problem after going through your suggested possible causes. I have done the Bank A thing; I've been going through the manual, and trying different methods of adjusting the WB, which as yet has not helped; and it is happening in RAW format; The white board outside in the sunlight comes out white; the Multiblitz lights don't seem to be the problem as it even happens outside. All other colours seem to come out as they should, it is only the skin tones that have this pinkish tinge to it - it's as if the sensor isn't reflecting skin tones very well. I am going to keep playing around with the camera as I really would like to know why this is happening. Like I said in my first email, it's fixable on Photoshop, but i'd like to know why it's happening. Unfortunately I don't have anyone nearby with a D100 that I can compare mine with! If you have any other suggestions, i'll be very happy to hear them!
Thanks again...

6/8/2004 5:28:27 AM

 
David Ziff

member since: 9/10/2003
 
 
  Natalya
Natalya
Indoors on camera flash with ambient daylight
© David Ziff
Nikon D100 Digital...
 
  Emily
Emily
outdoors no flash
© David Ziff
Nikon D100 Digital...
 
 
I have a D100 and I'd be happy to try to duplicate or test your results. If as you say "the sensor isn't reflecting skin tones very well" does that mean outdoors in natural light and indoors with flash as well? Or is it only under the lighting setup you have in the studio. I'm asking this as I've had no trouble with skin tones - in fact both with natural and artifical light they come out great. I'm doing to send you two photos, one with an Speedlight SB-800 and another outside in natural light outside. In any case, should there some test I can run with my D100?

6/8/2004 9:22:31 PM

 
David Ziff

member since: 9/10/2003
 
 
  Group of friends
Group of friends
Indoor in a Chinese restaurant, SB-800 flash, program mode
© David Ziff
Nikon D100 Digital...
 
 
sorry - here's the SB-800 flash

6/8/2004 9:46:46 PM

 
Deonne 

member since: 10/2/2001
  It appears to be happening in both situations. I am going away tonight for a month, and during this time i'll try to do some more testing, and will get back to you when I get home again.
Thank you very much for your help with this David - I appreciate you taking the time to respond and upload photos etc. I'll let you know what i've discovered in a month or so - hopefully with some good news!

6/9/2004 3:37:13 AM

 
David Ziff

member since: 9/10/2003
  Have fun. If I were you I would order and consult Thom Hogan's Complete Guide to the Nikon D100.
It's 280 pages of invaluable data that goes well beyond the manual. When in doubt learn more about something and it often resolves. That's my motto, at least.

6/9/2004 6:28:15 AM

 
William Koplitz

member since: 2/28/2004
  Try shooting this camera in manual mode and make sure the shutter speed is fast enough to not pick up any ambient light.

6/9/2004 7:09:55 PM

 
anonymous A. 

member since: 9/19/2005
  If the problem is with the camera, you have plenty here to solve it... but since you say it happens in RAW, that eliminates white balance adjustments and other in-camera processing. It suggests that the caste is in the environment before the image is recorded, or added after. That comes down to the lens or the light before, and the monitor or printer after.
I think you have pretty well covered the light issues, but that doesn't b]mean that there is no aberation coming the lens or filters: maybe a tinted daylight filter or an off-tint UV?

More likely is that your monitor and printer haven't been calibrated properly; maybe the colour caste is actually in the monitor image, not the file, maybe the colour is being introduced by the printer (or by your photo processor if you use a commercial printer). Finally, YOU might be introducing it during post-processing ~ some batch or automated function that's being run by your RAW conversion application or by Photoshop.
Hope you crack it soon...good luck.

1/12/2006 4:44:50 AM

 
David Earls

member since: 4/15/2005
  You can correct color cast in the image in Photoshop. This is John Shaw's technique, and it works for me:

1. Set the color sampler to 3x3 average.
2. Click the New Layer button, select Threshhold.
3. Move the slider to the left until there is only one spot of black. Put a color sampler on it.
4. Move the slider to the right until there's only one spot of white. Put a second color sampler on it.
5. Cancel the Threshhold layer. You should now have your original image with two color samplers on it, numbered 1 and 2.
6. Make sure the Info palette is open and that you've set it to display RGB values. You should be able to see the RGB values for the two samplers you clicked.
7. Create a new Levels Adjustment Layer.
8. Look at the R, G, and B values for color sample 1. You will be adjusting the levels of the two channels whose values are HIGHER than the lowest of the three values. You will move the left sliders on these two channels until their values agree with the lowest value. You are going to be clipping some color pixels during the process. Those are the culprits giving you a color cast.
9. Now look at the color sample values for sample 2. This time, you are going to move the right hand sliders on the two channels whose values are LOWER than the highest value of the three channels.
10. Click OK.

To compare pre- and post-corrected images, uncheck the layer visibility control. You can flatten the image at this point if you're satisfied with the results. It goes almost without saying that you don't flatten the new image until you've saved the unedited version.

Checking for and removing color cast is a good first step in correcting an image.

John's book on CD is an excellent source for image editing in Photoshop. It's available from his website. I can't recommend it highly enough.

1/12/2006 3:01:28 PM

 

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