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Author Topic: Color cast  (Read 6078 times)

dannyboy

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Color cast
« on: December 11, 2005, 12:53:15 PM »

I have been playing around with a friends 1DS and I have noticed a consistent greenish color cast throughout all the captures. No post processing was done. Where does a given color cast come from? Is it characteristic of a given sensor? I know it can be corrected with a curves adjustment in the green channel so my question is not how to fix it but more o do with the cause. Thanks!
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DarkPenguin

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Color cast
« Reply #1 on: December 11, 2005, 01:15:23 PM »

White balancing?
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Jonathan Wienke

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« Reply #2 on: December 11, 2005, 09:25:14 PM »

Or more likely, a poorly calibrated or uncalibrated monitor. Or are you shooting JPEG? Shoot RAW and calibrate your RAW converter and monitor and it won't be an issue.

dannyboy

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Color cast
« Reply #3 on: December 11, 2005, 11:52:12 PM »

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Or more likely, a poorly calibrated or uncalibrated monitor. Or are you shooting JPEG? Shoot RAW and calibrate your RAW converter and monitor and it won't be an issue.
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The monitor has been calibrated but I was unaware you could calibrate the RAW converter. How do you go about that? I am using the latest  beta version of ACR
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Jonathan Wienke

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Color cast
« Reply #4 on: December 12, 2005, 01:47:55 AM »

dannyboy

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Color cast
« Reply #5 on: December 12, 2005, 12:01:35 PM »

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http://www.visual-vacations.com/ColorManag...01/04camera.htm
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Thanks alot. So I am inferring that it is necessary to calibrate each individual camera as opposed to trusting the generic profile that Adobe or Canon use?
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Jonathan Wienke

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Color cast
« Reply #6 on: December 12, 2005, 01:16:59 PM »

Correct. What the calibration process does is fine-tunes the internal profile to match the specific camera.

dannyboy

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Color cast
« Reply #7 on: December 12, 2005, 05:36:15 PM »

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Correct. What the calibration process does is fine-tunes the internal profile to match the specific camera.
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Thanks Jonathan, You have been a big help!
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dannyboy

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Color cast
« Reply #8 on: December 16, 2005, 06:39:34 PM »

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I have tried many times to run the ACR calibration script as you suggested. I run the script and immediately get an error message in the White balance (Both in the Best Result line and the Current attempt.) The script continues to run and with each white balance pass states an error in the same lines. After several hours it gets to Green calibration and then the computer abruptly shuts off. I have sent several emails to tech support @ Chromoholics but have'nt gotten a response. Did you experience anything similar?
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Jonathan Wienke

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« Reply #9 on: December 16, 2005, 07:40:45 PM »

You have a major computer problem if the script makes your computer shut off. I couldn't say if it's a corrupt Photoshop installation or a hardware issue, but that's majorly bad juju, and the script author is unlikely to be able to help you.

Describe what lighting you're using to light the Color Checker; I'd recommend direct sun daylight if possible to ensure the entire Color Checker is lit evenly. If it's not lit evenly, or over- or under-exposed, the results will be skewed to the point where the script may not be able to calculate a usable result. Can you post your RAW online and then post a link to it so I can see it?

dannyboy

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Color cast
« Reply #10 on: December 16, 2005, 08:38:01 PM »

Yeah, it is probably some real bad juju. I was careful to follow the instructons that you posted on your website. I shot the RAW in direct sunlight and set exposure to not clip the whites when the Exposure slider was set to 0.0. I tried running the older script on PSCS with ACR 2.4 and got the same crash. I will look into posting a link to the RAW image. I think it must be the bad JUJU!
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Jonathan Wienke

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« Reply #11 on: December 16, 2005, 11:22:32 PM »

The script terminating with an error is understandable if there is simply a bug in the script. But shutting down the computer completely is very unusual.

dannyboy

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« Reply #12 on: December 17, 2005, 10:39:10 AM »

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The script terminating with an error is understandable if there is simply a bug in the script. But shutting down the computer completely is very unusual.
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Okay, one more question before I frag my computer. When you run the script is it normal to get an error with a numerical value at the end of both the Best Result and Current Attempt lines? The script continues to run irregardless and generates an error with a changing numerical value with each pass when calibrating WB
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Tim Gray

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Color cast
« Reply #13 on: December 17, 2005, 12:25:15 PM »

I've run the utility a couple of times and never had an abnormal termination or any kind of error.

Why don't you attach the sample shot of the color chart you're using.  (File Attachments 2 boxes down from the "enter your post" section.)  Apparently you don't need to have the files hosted anymore...

FWIW, I would expect the the callibration process to have a fairly subtle result - I'd be surprised if a particularly noticeable color cast were the result of a camera callibration issue.
« Last Edit: December 17, 2005, 12:26:01 PM by Tim Gray »
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dannyboy

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Color cast
« Reply #14 on: December 17, 2005, 02:34:22 PM »

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I've run the utility a couple of times and never had an abnormal termination or any kind of error.

Why don't you attach the sample shot of the color chart you're using.  (File Attachments 2 boxes down from the "enter your post" section.)  Apparently you don't need to have the files hosted anymore...

FWIW, I would expect the the callibration process to have a fairly subtle result - I'd be surprised if a particularly noticeable color cast were the result of a camera callibration issue.
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Jonathan Wienke

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« Reply #15 on: December 17, 2005, 09:35:46 PM »

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Okay, one more question before I frag my computer. When you run the script is it normal to get an error with a numerical value at the end of both the Best Result and Current Attempt lines?
I have never encountered that, and I've calibrated 2 versions of ACR (2.x and 3.x) for 3 different cameras (10D, 1D-MkII, and 1Ds). I'd try uninstalling and reinstalling Photoshop (making sure to remove all the preference files) as a first step, and if that doesn't help, seek professional assistance.
« Last Edit: December 17, 2005, 09:36:13 PM by Jonathan Wienke »
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dannyboy

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Color cast
« Reply #16 on: December 18, 2005, 06:15:02 PM »

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I have never encountered that, and I've calibrated 2 versions of ACR (2.x and 3.x) for 3 different cameras (10D, 1D-MkII, and 1Ds). I'd try uninstalling and reinstalling Photoshop (making sure to remove all the preference files) as a first step, and if that doesn't help, seek professional assistance.
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It has to be my computer because I ran the script pn my laptop and it executed just fine. This leads to another question. Is the script conclusions ar all linked to the monitor profile? In other words, can I plug the calibration values generated on the laptop back into the desktop?
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Tim Gray

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Color cast
« Reply #17 on: December 18, 2005, 07:33:07 PM »

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It has to be my computer because I ran the script pn my laptop and it executed just fine. This leads to another question. Is the script conclusions ar all linked to the monitor profile? In other words, can I plug the calibration values generated on the laptop back into the desktop?
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Has nothing to do with the monitor profile - the script just adjusts the as shot colors to the objective standard of the GMB color chart.  It's unique to your camera, not the monitor.
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dannyboy

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Color cast
« Reply #18 on: December 18, 2005, 07:38:33 PM »

Thank you guys for all of your help.
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Jonathan Wienke

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« Reply #19 on: December 18, 2005, 08:44:02 PM »

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This leads to another question. Is the script conclusions ar all linked to the monitor profile? In other words, can I plug the calibration values generated on the laptop back into the desktop?
As Tim said, the monitor profile is not involved, and you can use the script calibration results on any machine running the same version of Photoshop + ACR that you may use to open RAW files from that camera.

But I'd definitelu have the desktop checked out before doing any serious work with it; you may have a virus or something causing the script problem.
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