Postprocessing White Balance & Color Correction Questions

JK1231JK1231 Posts: 24Member
edited October 2013 in General Discussions
Okay, I'm definitely going to make myself sound dumb here... but I'm frustrated.

I'm using Aperture for postprocessing my raw images and I'm going insane trying to figure out how to properly balance color. (I also have CS6 installed, but honestly haven't been brave enough to venture down that path as Aperture's color correction is giving me enough grief.) Until recently, I've been happy with "mostly correct" color (as I'm sure applies to most people!) but I've done some recent stuff where I'd like to get really accurate color, even under less than ideal lighting.

I'm shooting a D7000 with various lenses, and either auto white balance or ExpoDisc corrected white balance.

Here's an example: I have a shot of a white+18%gray+black card. When I auto-adjust on the 18% gray, I get RGBL all set to 125 (as indicated by color values in loupe). However, white ends up at RGBL of 196+191+255+196 and black ends up at RGBL of 25+26+25+26. Needless to say, the image has a blue cast and black is muddy. What is the proper way to get rid of the blue cast without hosing the rest of the colors? When I try to adjust the white to be closer to all 255 (something in the 220s or higher), black becomes gray and the 18% gray develops a yellow cast (as does the rest of the image).

I have an even worse problem when I shoot a color card and try to correct the colors. I can usually get one or two colors close to correct, at the expense of the other colors being way off. It would seem to me that this should be a problem that software should be able to fix without a lot of manual intervention: You shoot the color card, you tell Aperture or Photoshop which vendor's card you just shot, and it should be able to "magically" adjust all the colors for you. I'm obviously not understanding something, but what?

I'm hoping someone can give me some clues as to how to do proper color correction, because I'm obviously missing something!!

HELP!

JK

Comments

  • MsmotoMsmoto Posts: 5,396Moderator
    Is your monitor calibrated? If not, you may never be able to get the color corrected as you might want. Here is a color cord you can download and look at on your monitor and someone else's iPod or something.

    http://www.flickr.com/photos/fantinesfotos/6823093006/in/set-72157630044833773

    This is a common card, but if you note, the black is not fully saturated nor are colors fully accurate. The point is I can use it as a reference when finalizing images. All monitors are different, even those calibrated.

    I am not a user of all the numbers, what I look for is the final effect. But, if you want to see what I consider decent color, look at these:

    http://www.flickr.com/photos/fantinesfotos/sets

    The light source is what I see as critical. This varies from morning to evening outdoors, clouds, and other atmospheric conditions affect it as well. Then at night, mixed color temp light sources can really be a nightmare.

    And, true confession...on my D4 I use auto WB almost 100% of the time as I always adjust in post. And, in some cases using the brush to locally alter the color balance may be necessary.

    Next you will hear from those who actually know what they are doing...LOL
    Msmoto, mod
  • tganiatstganiats Posts: 131Member
    I agree it may be a monitor problem. Do you see it in prints, too?

    That said, are you 'eyeballing' the color balance in Aperture, or having Aperture do it with the eyedropper?
  • JK1231JK1231 Posts: 24Member
    Apologies for short answers... but I only have a sec.

    Monitor calibrated using Spyder. (I should have put that in original question... duh!)

    Problem is in prints, too... using a calibrated printer.

    Aperture WB set by using eyedropper.

    I know problem is light source based, but I would have thought that I should be able to correct it to adjust for missing / excess colors in light source. Don't understand why I seem incapable of doing so! :(
  • haroldpharoldp Posts: 984Member
    I use Capture NX2 for Nikon raw processing for this reason.
    I use CS-6 and ACR for Leica and Fuji raw, and Adobes color mapping of those sensors is close enough for non-critical looks but not nearly as good Nikon / NX2.

    Users in the Leica community have posted acr profiles or m9 / m8 which help.

    Unless somebody can provide one, you will have use adobes profiling tool and build a profile.

    In all other respects NX2 is not as good as CS-6 and ACR, but this one maters to me.

    regards ... H
    D810, D3x, 14-24/2.8, 50/1.4D, 24-70/2.8, 24-120/4 VR, 70-200/2.8 VR1, 80-400 G, 200-400/4 VR1, 400/2.8 ED VR G, 105/2 DC, 17-55/2.8.
    Nikon N90s, F100, F, lots of Leica M digital and film stuff.

  • AdeAde Posts: 1,071Member
    edited October 2013

    Here's an example: I have a shot of a white+18%gray+black card. When I auto-adjust on the 18% gray, I get RGBL all set to 125 (as indicated by color values in loupe). However, white ends up at RGBL of 196+191+255+196 and black ends up at RGBL of 25+26+25+26. Needless to say, the image has a blue cast and black is muddy.
    Just thinking out loud here.

    I think you may have two separate issues. First, the gray RGB level at 125, 125, 125 and black at 25,26,25 suggest a slight overexposure.

    Second, "white" paper stock and white fabric are often produced with generous amounts of optical brighteners. These brighteners fluoresce under UV light (including UV from sunshine or a camera flash) to produce a bluish tint. Some camera flashes output more UV light than others, and some types of white paper have lots of brighteners in them.

    The combination of the slight overexposure, and the effect of the optical brighteners, could cause a white card to turn bluish.

    Still, the RGB value of 196,191,255 is really extreme for this scenario (the blue channel is completely blown) so maybe the problem is elsewhere. Some older Nikons (like the D1) were very sensitive to UV to the point of needing a UV filter in some situations.

    You could try to test by finding a white paper formulated without optical brighteners, and/or using a different light source (with low UV output).

    (Good gray cards are produced on special paper without brighteners. White fabric, on the opposite end, often get lots of brighteners from common laundry detergents.)
    Post edited by Ade on
Sign In or Register to comment.