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In which I field complaints about my C300 matrices, and commit to fight anew...

By Art Adams | February 05, 2013

I've been getting sporadic complaints on Twitter about one of my C300 matrices turning reds a bit blue on some cameras. Time to take another look…

In this article I wrote about how I endeavored to match the color of a Canon C300 to an Arri Alexa. At the time, according to the scopes and the monitor I used, I'd succeeded. I've now gotten some complaints, including pictures, saying that my daylight look makes reds look a little purple on some C300s. It seems that different versions of the camera's firmware may result in different colormetry.

I'm going to go through my matrices again on Friday and see what I can figure out. I probably won't call the new version "Alexa emulation" matrices because the matrices I built do seem to match the Arri Alexa's beautiful color according to a test chart and high-end monitor, at last in accuracy if not in perfect saturation, but there's much more going on beneath the surface of Canon's color that I don't understand yet. Instead of attempting to replicate Arri's look I'm simply going to aim for color accuracy instead. (In essence, though, that is Arri's look.)

I played around with the C300 matrices yesterday during lunch on a shoot and was reminded just how hard it is to get both red and flesh tone dead-on accurate at the same time. Also, Canon cameras really emphasize red, probably because they put flesh tone ahead of all else, and there may be a very good reason why they tend to cheat red a little toward orange in most of their matrices:

If your camera's colorimetry really punches up red, it's always better to err on the side of orange-red than blue red so as to avoid compromising flesh tone as well as dulling bright reds.

To my eye, anyway, I find orange-biased reds less offensive than blue-biased reds, and I suspect Canon feels the same.

I'm not defeated yet. I'm going back into Chater camera on Friday and I'm going to tinker around some more. I really do want to try to get accurate reds and flesh tones at the same time. Getting an accurate blue doesn't seem to be difficult, although I suspect that--like most cameras--I won't be able to nail flesh tones and green at the same time, at least under tungsten, but green is one of those colors that can drift a little and we don't seem to care.

What's interesting is that I was a little nervous about the tungsten matrix because I tweaked phase, which seems a bit to me like cheating, and yet that matrix seems fine. That may be my starting point in the future: rotating phase to make red accurate, and then nudging the other vectors to perfection… or as close as I can get. (I did that in the matrix I show below and ended up doing very little tweaking.)

It is interesting, though, to note that Canon's color, while not accurate, can be very pretty, and it's clear they've learned which way to nudge hues to get what they think is the best look out of their camera. They put flesh tone first and foremost: people will always look great. The other colors will look good, but maybe not accurate.

Matrix adjustments are very tricky things because every element interacts. Tweaking saturation in one color means adjusting hue in another. Complementary colors interact as well: reducing blue saturation, for example, reduces yellow saturation also, and as yellow is a major component of flesh tone it may be best to leave blue saturation alone and punch up everything else to match.

If you're one of those people who are getting blueish reds from my previous daylight matrix I cobbled up a temporary one on set yesterday that may be worth trying. The regular disclaimers apply, which can be summed up as use at your own risk. These numbers are provided as a courtesy, and for fun, so before using them professionally please test, test, test.

Phase: +11
R-G: 0
R-B: 0
G-R: 0
G-B: +21
B-R: 0
B-G: 0

Gain to taste.

More after my trip to Chater Camera on Friday.

2/5/2013

Art Adams
Director of Photography
www.artadamsdp.com
Twitter: @artadams

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Comments

Bob Kertesz: | February, 06, 2013

In my experience, very precise color rendition is only mandatory in product shots, and useful in B roll cutaways, and then, if it’s important, post tweaks those to within an inch of their lives anyway.

No one is really sure what color that building or park bench or vase in the shot should be, but everyone knows (or think they know) exactly what flesh tone should look like. I always work toward getting the best possible flesh tones, wherever anything else falls.

And don’t forget that we do ‘internal’ color correction and interpolation as well - the color temperature of the monitor in use, and the color temperature of the surrounding area, biases us in certain ways. For me, a red that falls exactly into the small red box on a vectorscope usually looks very slightly too blue on most monitors, for instance.

Since matrix changes to basic colorimetry tend to be somewhat noisy and destructive, I try to avoid using them on 8 bit cameras and recordings, although it is, of course, sometimes necessary.

—Bob

Art Adams: | February, 06, 2013

I completely agree that precise color rendition is not mandatory, but I’ve found that I do prefer it. Rec 709 color on an Alexa appears very “real” to me, and it often comes close to matching what I see by eye. I just prefer it when colors look like what they really are.

Color in the C300 didn’t become an issue for me until I shot a spot in front of the Golden Gate Bridge and EOS Standard matrix was the only one that rendered the bridge anything other than flat orange. I also noticed the grass was a bit cool in the other matrices but looked healthy and green in EOS Standard. That’s when I decided I was going to try to recreate the look that I love in the Alexa in the C300.

Most cameras take liberties with color in some way or another and we never notice, but for my preference I like it when colors are a bit more real. Maybe my next step will be to create my own looks by pushing the colors in different ways.

As for noise from pushing the matrix around, yes—there are some situations where I’ve seen that, mostly under tungsten light when I’ve tried to get yellow and green in their boxes at the same time. It just can’t be done. I’ve tended to avoid phase for some reason, but I think now I’m going to use it to put the colors as close to their boxes as possible and use the matrix itself for minor tweaks. I did that with the matrix above and it came out very clean and pretty, which no extra noise.

Your comment about “normal” reds looking a little cool on monitors is interesting. Hmmm…

Bob Kertesz: | February, 06, 2013

I don’t have a problem with the Alexa’s REC709 color rendition, but I do with their gamma curve. For me, it tends to compress the lower mids (the area between, say, 20 and 40 IRE) excessively, giving a more contrasty look than I like. The one it originally shipped with was really horrible. The current one is better, but not anywhere near as pleasing as Sony’s or Panasonic’s, for instance.

Having said that, I am somewhat envious of your ‘need’ to shoot in 709. Being the control freak I am, I prefer to set the look rather than shoot a “fat neg” that will then be tortured in post smile. I rarely get to do that any more, except on sitcoms.

I will be interested is your results tweaking ‘phase’. I haven’t done it on the Canon, but on Panasonics, the amount of noise that introduces (in their “color corrector” menu settings) is pretty severe…

—Bob

Art Adams: | February, 06, 2013

I’d rather shoot flat and do some nice tweaking in post, honestly, but in my market we’ve swung from color correcting everything (thank you, RED) to color correcting nothing (thank you, F3 and C300). I don’t want to shoot with Princess Alexa in Rec 709 only mode, but I can often sell production on an Alexa over, say, an Epic, just by pointing out that we can get a great looking image that only requires minor post tweaks rather than committing to a full-on color correction session.

As the Alexa offers great color as well as improved highlight handling over the Epic (without HDR) I can usually sell that option.

These days I’m often working without a DIT or a video engineer on set (unheard of in my market six or seven years ago) and what I shoot will never be touched again… so I’m highly motivated to get it right the first time. smile

I think next time around I’m really going to focus on using phase to get colors as close as possible to where I want them as that doesn’t seem to add noise. From there the tweaks should be fairly subtle. It was when I avoided using phase that I had to get aggressive.

Don Platon: | February, 07, 2013

Posted a test of the ARTALXA5 picture profile using a C300 with firmware upgrade here: https://vimeo.com/59198695 The l.ook is stunning. Still to do a daylight test using the second picture profile. Thanks, Art!

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