c300 - C-Log - completely inaccurate colors! Do we have a bad unit?

[Matthew Bennett]

After doing some testing with my companies c300 last week, we determined that the cinema lock (c-log) mode, and the cinema picture profiles have completely inaccurate colors!

Greens were skewed into blue, and reds were skewed into orange.

The Test:
Very simple, just a quality grey card, macbeth color checkers, human face, and some problem fabrics in the shot.
Shot both daylight and tungsten. Metered shot, grey balanced off the card, and then checked for balance with the RGB waveform.

The Results:
Some of the picture profiles we tested had correct colors. The EOS standard was the most accurate.

C-Log was radically skewed. Grey was correct, and the face was correct. But the green turned blue, and deep scarlet red turned orange.

(UPDATE) July19,2012

We tested another camera against ours today. Exact same rendering of the green color! (As cyan).

If for some reason this is standard for the camera, C-Log is now unfortunately useless for any work involving accurate color reproduction.

Hmmm. Time to talk to the Canon Head Office.

3_C300_color_compare.jpg

[cowpunk52]

Sounds strange - my experience in testing has been the complete opposite. C-log has been the most accurate for me, while EOS has a pleasing but exaggerated color profile.

Is this what your camera looks like?

CanonLog.jpg

[Matthew Bennett]

I'll post grabs on Monday, all the test shots are at my office.

Thanks for responding Cowpunk!

[Matthew Bennett]

Posted grabs.

Actually the red looks semi-okay in the grabs, but we've had some problems on a shoot (branded soccer jerseys turning orange..)

[Matthew Bennett]

I'll assume that with this many views - no one has really had much problem with accurate colors on this camera.

[escozooz]

my guess is that you are color correcting the Canon Log improperly. Can you post the curve you've been using to color correct the footage? I find in Apple Color and DaVinci that you mostly adjust the bottom 1/3 of the curve the most directly.

Your stills look to me like you've pull the mids too far up.

[bill totolo]

You can't trust color accuracy in FCP.
Also, have you bypassed what Apple is doing to your colors by using a Black Magic Intensity Pro card?

[Matthew Bennett]

my guess is that you are color correcting the Canon Log improperly. Can you post the curve you've been using to color correct the footage? I find in Apple Color and DaVinci that you mostly adjust the bottom 1/3 of the curve the most directly.

Your stills look to me like you've pull the mids too far up.

It was just the fcp color corrector for a quickie contrast addition. Not normal practice, just something to quickly show the color distortion.

We worked the same footage in Apple Color and After Effects, with similar results - the green color of the shirt is being completely mis-represented in C-Log as well as many other picture profiles we tested.
I'm not a camera engineer, but this behaviour from a camera is bizarre, and well - unacceptable as our work is based around strict color accuracy. (as I'm sure pretty much everybody on the planet's is.. ;))

Anyway, we're taking it back and getting it replaced...

[Matthew Bennett]

You can't trust color accuracy in FCP.
Also, have you bypassed what Apple is doing to your colors by using a Black Magic Intensity Pro card?

The curse of fcp..

Haven't tried a BMD card even though we have one at the office...

The clincher is that some of the picture profiles reproduce the color well (varying degrees), with EOS STD being almost perfectly accurate.

We're going to test another c300 unit against ours, same setup, and see if the results are the same.

[Dino]

Matthew, my experiences are similar to your findings. Green is skewed to cyan in Cine gammas with low saturation. When shooting green screen with Cine gammas, the green looks blue. It is possible to go into the matrix and adjust for REC709 with a Chroma Du Monde chart.
There is also the zone based color correction circuit, but I haven't figured that out yet.

For what it's worth, I've had similar experiences with Panasonic cameras being green deficient out of the box, but in the case of the 2/3" high-end cameras, very easy to get accurate color points with matrix and color correction menus. I've had the same issue with EX1's, but harder to correct.

Here are my matrix color points for a more accurate REC 709 C300 file, this is just a rough baseline, but should get you closer:

Gain +41
Phase +6
R-G -31
R-B -28
G-R +3
G-B -39
B-R -8
B-G +12

Hope this helps, YMMV.