My GretagMacbeth ColorChecker Sample - CORRECTION

Discussion in 'People' started by Joe Marques, Mar 1, 2005.

  1. Well I guess this is another thanks to Todd for his post which reminded me that I actually had the colorchecker (and scarcely used it until now).

    Here's how I used it to color correct a few natural light images today that the D2h meter made a bit too blue on auto (I posted a few of these shots earlier under the 50 1.4D thread with no cc).

    Here's the test shot:
    40341375.
    I used the test shot to create a custom curve in NC 4.2 which I applied here:
    View attachment 5780

    I know the corrected images look warm but trust me they're much closer to reality than the original shots. Look at the whites of her eyes in the processed shot - they're still white and not "orange" (which is what they'd look like if the shot was too warm). Also look at her hands - the right-side shots are much more accurate since she's not that pale.

    I think the side-by-side exaggerates the warmth due to the originals being too cold. The GAP sweatshirt is another key here for me - it's a fairly saturated PINK color, not pale pink as depicted in the left-side images.

    BTW, these are ONLY color corrected and resized. In a full process I would certainly raise the gamma to bring out more shadow detail and her eye color.

    CORRECTION: Using ACR I found that clicking the gray box 2 spaces from white yields excellent results (and it's far quicker than my long process in NC). Again, the goal here is ACCURACY and these look more accurate.

    While I might tweak a shot to make it warm, I want the most accurate color to start and now I think I have it. These look far more natural than my NC results which I now realize ended up too warm (hey, I'm not afraid to admit when I'm wrong). :wink:

    Here are my updated test shot with what I think looks like more accurate color and obvious improved shadow detail:
    View attachment 5781
    View attachment 5782

    Sorry for the reversal here but I'd rather get it right than too proud to admit I was wrong. :D

    Joe
     
  2. Really shows how valuable the Gretag Macbeth color checker is. You definitely need something that will help you get the colors right. Auto simply doesn't do the job in many situations. Thanks Joe.
     
  3. The first thought that ran through my mind was "what a warm photograph". Just as you descibed it. Great shots.
     
  4. Re: My GretagMacbeth ColorChecker Sample

    Hi Joe...
    the color checker is a very valueble tool... it takes all the "creepy" light and bad color out :D Very handy for your case I presume :lol:
     
  5. Re: My GretagMacbeth ColorChecker Sample

    Would you please walk us duffers through how you created the profile and uploaded it to the D2H? I'm going to get a color checker this weekend.

    Thanks very much, Rich
     
  6. Todd_D1x

    Todd_D1x

    70
    Feb 23, 2005
    Austin, TX
    Re: My GretagMacbeth ColorChecker Sample


    Alright Joe! Looks good dude. That is a cool tool is it not? So i guess for this shot, did you use the eyedropper tool to set the white, gray, & black points? Usually if you do the D-lighting it really helps brings to bring out the shadows nicely when the best quality is selected. Anyway, I would use this for your wedding, have the bride hold during one of the shots in all the lighting conditions, it will help just like this. Well Cool Dude, great job!

    Todd
     
  7. I find this process is the most efficient way to set WB for a shoot and be assured that you have accurate color. I'm no expert, of course, and would expect someone like Iliah to offer greater depth to this discussion.

    Regards,

    Joe
     
  8. Thank you PhotoDawg. I'm a big fan of warm and saturated, that's why Velvia was my film of choice.

    Joe
     
  9. Re: My GretagMacbeth ColorChecker Sample

    Hi Panos, glad to see you're here. My daugther doesn't share my "creepy" genes. :D

    Joe
     
  10. Re: My GretagMacbeth ColorChecker Sample

    Hi Rich,

    I wouldn't use this approach to load a curve on the D2h since the curve would only be good for that exact lighting. Instead I simply save the curve I created by processing the image in NC and then load the curve on each subsequent image (I'm guessing I could batch process as well).

    Here's how I make the curve. I mark the black, white and gray squares (the gray square 2 places away from white) using the NC equivalent of the eye dropper tool. I then adjust each channel to equalize the numbers (meaning if my white square is RGB values of 230, 210, 241 - then I will slide the right side of the curve for each channel and until they all reach the same number. Figuring out which number is the trick).

    Sometimes the white square isn't the brightest spot on the shot so you don't want to make it 245/245/245 or you'll blow image hilights. On this shot I made the white box 220/220/220 IIRC in order to keep her left cheek under control (since her left cheek was brighter and close to 245 after tweaking). I repeat the process for the black box with values of 28 or so.

    For the gray box it trickier. You must tweak the gamma of each curve to the average of the 3 values and then re-check black and white to ensure they're still equalized (since B and W values may drift in NC since you can't lock the ends of the curve like you can in PS). In the end I have black, white and gray values that are nearly equal (e.g., black 29, 29, 30 - gray 130, 131, 129 - white 220, 222, 221). This ensures a neutral photo - meaning no color cast.

    Regards,

    Joe
     
  11. Re: My GretagMacbeth ColorChecker Sample

    Thanks buddy. I didn't like the d-lighting in NC and would prefer to bring out shadow detail in PS where I feel more confident using curves and the shadow/hilight tool. I plan to use it for the wedding. Thanks again for your help.

    Joe
     
  12. Wow! I'm sold. That card is in my next order from B&H/Adorama.

    Thanks for the beautiful examples,

    _/oe
     
  13. Steve S

    Steve S

    Feb 1, 2005
    SE Florida
    Wouldn't it be better to just get the GretagMacbeth ColorChecker® Three-step Gray Scale Card, since it has only the 3 colors you need, and costs less?
     
  14. Bump

    Very Good question since B&H wants $66.95 US plus shipping. Would one ever use anything other than black, grey and white.

    Illiah? Anyone?

    Rich
     
  15. I would guess you could use the other panels for doing a simple printer calibration, I dunno. I think I read that the browns are similar to skin tones so maybe something there as well.

    The price difference is only $7 between the two...

    _/oe
     

  16. Another great use of the full ColorChecker is to calibrate ACR by taking a shot of it and following Bruce Fraser's tutorial:

    http://www.creativepro.com/story/feature/21351-1.html

    Joe
     
  17. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    First of all, it's not only three patches that are useful - one can colour-correct non-linear colour reproduction using colour patches as well; and correct overall tonal response using curves and other gray patches.

    BTW, try AWB from Macbet Color Checker and copy it to next shots in same light. You can also try AWB with +/- - to see wich one works better for you.

    Systematic usage of ColorChecker is by using curves in colour channels to correct tints according to known values of ColorChecker patches.
     
  18. Always great to have your expert insights noted. :D Glad to see you're here Iliah.

    Regards,

    Joe
     
  19. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Joe, do you have reference image/data for colour correction using ColorChecker?
     
  20. Of course not. I don't even know what that means. :D I'm usually the "techie" in the room, until you enter. 8)

    So please, enlighten me.
     
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