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Old October 19th, 2012, 05:24 PM   #1
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Should I use a color chart for post-production color-correcting?

I'm a newb to color correction, and I recently came across an interesting tutorial video on color correcting using the Photoshop RGB Curves effect to numerically match the white, midtone gray, and black color values. My question is, to do this truly "correctly," is it necessary/useful to have a color chart of the following kind in order to get correct neutral color reference points while shooting?
The Macbeth Color Checker
Accu-Chart Accu-Chart 9 Step EIA Type Grey Scale Chart Video Test Charts at Markertek.com
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Old October 20th, 2012, 08:43 AM   #2
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Re: Should I use a color chart for post-production color-correcting?

The most important part of grading and color correction is monitor calibration. Once your monitor is true the only thing a chart will do is allow you to get a very accurate reproduction of the original scene. However very often what you want is an artistic interpretation of the original scene and a chart is of little help in that case.
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Old October 20th, 2012, 09:38 AM   #3
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Re: Should I use a color chart for post-production color-correcting?

Alister,

I agree that this is somewhat useless for color grading (unless you want to color correct BEFORE grading), but for the numeric calibration using the specific RGB color values, I need to depend on more than just my eyes looking at a calibrated monitor. For this, if what I'm looking for is simply neutral colors, then I thought simply shooting a second of a color or greyscale chart would be of use.
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Old October 20th, 2012, 10:40 AM   #4
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Re: Should I use a color chart for post-production color-correcting?

Quote:
Originally Posted by Natan Pakman View Post
I'm a newb to color correction, and I recently came across an interesting tutorial video on color correcting using the Photoshop RGB Curves effect to numerically match the white, midtone gray, and black color values. My question is, to do this truly "correctly," is it necessary/useful to have a color chart of the following kind in order to get correct neutral color reference points while shooting?
Probably not. If you could create an ICC profile for your camera, you'd need a much more complex chart, and you'd have to do it for just about every scene you capture, because the lighting will be different every time, and changing the lighting invalidates the profile. So... people don't do it. More trouble than it's worth.

What appears to be more-or-less standard practice is to use a gray card to completely fill the camera's field of view, somewhat out of focus, and do a custom white balance before every scene. This allows the camera to take out most of the spikes in the lighting (goes a fair way to getting rid of green spikes under fluorescents for example), and gives the camera a fairly accurate neutral axis. And that's about as far as you can reasonably go. Reasonably being the operative word here.

First thing you do though, is pick up a copy of http://www.amazon.com/Color-Correction-Handbook-Professional-Techniques/dp/0321713117 One of the very best technical books ever. Tells you what you need to know in an order that makes sense, and it's really readable. Highly recommended. Will answer questions you didn't know enough to ask.
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Old October 20th, 2012, 11:01 AM   #5
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Re: Should I use a color chart for post-production color-correcting?

I wouldn't because if I get lost and need to get a neutral balance as a starting point, there's probably something in the shot that's close to grey that I can use. Otherwise I'd just go with my gut. It's far more important to have consistent balance throughout a scene and between scenes. Some scenes I want a different feel so balance means nothing in that case. GL
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Old October 20th, 2012, 11:21 AM   #6
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Re: Should I use a color chart for post-production color-correcting?

The primary use of the grey chip chart is in matching multiple studio cameras *prior* to rolling. In this use, a video engineer would have access to image controls on each color channel.

Could you have some fun learning about color correction with the aid of a color chart or gray chips? You bet. But I would see it that way, as a learning tool for when you have time & motivation.

Most small camera users are going to have some basic choices for the shoot, like ND, Gain, Iris, WB, and any black stretch/Gamma their cam might offer. Neither color nor grey chips is going to help in these situations without a waveform monitor, and perhaps vectorscope.

With this test equipment and charts, you can dial in your camera with confidence, to the extent your cam is dialable.

Of course some cams now incorporate scopes, very handy for those who know how to use them. I've been recently using a Panasonic HMC150 and a Canon 60D with Magic Lantern, the scopes are very helpful. Hardware scopes are used in many studio shoots, and Adobe's OnLocation software scope and BlackMagic's UltraScope are small enough to use with a laptop on location. But, I've not seen the need for charts in the field. If I had multiples of these cameras, I'd take them to my fav video engineer and get his help in checking how they match.

But, it sounds like you're talking about a single camera. The advice above is good. Avoid mixed color temp lighting, custom white balance each scene, use zebras to avoid overexposing, try not to use gain - good enough to get to post.

Then, it's all about the post look and aesthetic you're going for. Lots of learning on how to define that look, how to get to it, and how to do that consistently across multiple scenes. Charts will tell you something, yes. But this is really about training your eye to see the scene, and a trained eye doesn't need the very limited help a chart provides.
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Old October 20th, 2012, 04:44 PM   #7
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Re: Should I use a color chart for post-production color-correcting?

Excellent suggestions all, and Bruce, you're the second person to recommend Color Correction Handbook, and it has great reviews, so I'll look into taking a look at it.
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