Exposure of caucasian skin tones on the C100 mk ii

[tomsemiterrific]

I don't want to beat a dead horse, and I'm sure this topic has been discussed ad nauseam, but, alas, I'm going to ask it again. Using a waveform monitor and grey card, what is the best setting for skin tone exposure on the C100 mk ii. The C100 is new to me, and I've done some experimenting--and the best I can judge I get consistently better facial and skin tone images with the grey card expose at about 40 IRE. Now, I'm not speaking about LOG. I'm just talking about one of the Custom Profiles Canon provides. But I would also be interested in correct grey card LOG exposure as well--but it's not my primary concern here. All I know at this point is I believe I get better results with skin tone at 40% rather than 50% with most all of these custom profiles as well as the image void of any of the profiles.

What other methods other than a waveform are also effective on the C100 mk II?

Could someone older and wiser (or just wiser would suffice, enlighten me further on this matter? As always, thanks for your kind attention.

[User]

Hi Tomsemiterrific

I'm in a bit of a hurry here but here are some notes that I've collected over the past few months. Hope this helps.

Canon C-LOG

18% Middle grey = 32.79% IRE

90% White = 62.74% IRE

http://www.dvxuser.com/V6/showthread.php?300371-how-do-I-know-I-m-properly-exposed-when-shooting-in-C-log/page2&s=d408a43004d503887fd6bc7fd4a2ab77

On another forum, James Longley, who has been using C-log for his Afghanistan documentary, posted this:

"One thing about exposure: Don't overexpose the C300. Just set the zebras at 90% (+/-5) and don't let anything go over unless absolutely necessary. You may think that the shadows are gone, but they're not. The camera is very forgiving – you get so much more than what you can see of the darks on the LCD screen in daylight. You have to just have faith that the shadow detail will be there when you bring the material home."

It is always important to test, but I think you can expose highlights in C-log up to 90% on a waveform.

Using a lower ISO won’t cause more noise, but will result in less dynamic range, in particular in the highlights. Instead of using a lower ISO, use an ND filter. Also, to reduce noise, I recommend overexposing by about a half stop. Canon doesn’t recommend this, but Shane Hurlbut does and my testing has confirmed that this camera needs a little extra light to keep the noise down.

Ebrahim Saadawi:

Activate waveform, expose until just before 100%. Trust me, this is the best image for the C100 C-Log in noise, DR, colour, skin. You'll see when you try it. The image is so much thicker and nicer when brought down while falls apart while pulled up. It's so easy to expose as the waveform is super fluid (real time at 25 fps). And yes ETTR even by pumping up ISO, on the C100 an under exposed 850 image is noisier than an ETTR 3200 image. But ideally, ETTR with iris and shutter and lights at 850 native ISO. 

Yes if you don't want to spend the huge effort of neat video in post, in shoots where you're going above 6400+ ISO, increasing the NR to 5 in the menus gives a ENORMOUS lowlight advantage with no detail loss. Beyond that you start losing. 

Also test using WDR instead of C-Log. Especially for +6400 ISO with +5 NR. I would actually shoot the first one shot in WDR at 850 ISO under sunlight just to avoid the initial momentary disappointment  you might get with seeing your first shot in C-Log, especially if it's in lowlight, with Cinema Lock (no DR) and exposed down a bit. WDR serves GREAT in fast jobs, some people even prefer it for grading. So compare both too as a test. 

http://www.hingsberg.com/index.php/2013/01/canon-c-log-exposed-literally/

The chart below that I put together is based on information provided from Canon’s whitepaper on C-LOG. From the chart you can see how image brightness values are remapped to new values. For example 18% middle grey which is normally 50%IRE moves down to around 32-33%. 90%IRE (white) will appear on your waveform monitor at only 62-63%. It’s really important to use these new values (even if you don’t understand them) when setting your exposure in C-LOG mode since it will maximize the dynamic range your sensor is capable of and preserve as much of the scene information as possible. This “maximum” amount of information is needed later when you de-LOG your footage and begin grading and color correcting in post.

http://blog.abelcine.com/2012/10/05/working-with-canon-log/

http://www.hdvideopro.com/columns/help-desk/the-rules-of-log-exposure

Canon C-LOG-18% Middle grey .textClipping

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[tomsemiterrific]

This is all great information. Thanks for posting it. For the work I do shooting log is irrelevant, though I do use the WDR custom profile and grade in it. One question: the chart you included--are those settings for ITU709, or for C LOG?

thanks again for taking the time to post these.

[User]

No sweat Tomsemiterrific, under the gun here but happy to help when I can.

I believe these 'values' are for C-Log. But take a look at this thread an contact Cinegain as he (to his credit) put this chart in front of me:

And please, feel free to update this thread with your result which are valuable to us all!

[Cinegain]

That's the beauty, it shouldn't matter, because your project ultimately isn't working in C-Log colorspace. And the assumption is that you're basing your corrections offa the waveform/vectorscope within your project (not the footage) read-out as well-lit skin should appear already color corrected. That doesn't really change, as Larry states: our brains are programmed to know three colors: blue skies, green grass and skintones. Working with greyscales and the skintone line allows us to have a reference that shouldn't look off. Of course these are just guide values and ranges and apply to well-lit skin, which might not be the case in your scene, or perhaps you were shooting the Hulk or some fellow from Avatar. But you could correct a whole scene, just by nailing bare well-lit skintone. So you do have to eyeball the ultimate tweaks. But those general values should get you darn close. The video that goes with it shows it nicely I think...

You might want to check this Color Correction Handbook by Alexis van Hurkman : http://www.amazon.com/Color-Correction-Handbook-Professional-Techniques/dp/0321929667 who talks in great depth about this. The actual referenced book in the video: the Encyclopedia of Color Correction is from 2006, the later Handbook (2nd ed) from 2013.

P.s. I'm no authority on color correction or Canon footage, I'm just a guy who conviently comes across the helpful stuff of others.

[Inazuma]

Shooting CLOG, I ran into a lot of problems with high amounts of noise and compression artefacts when grading. This was mostly solved by exposing like Ebrahim said - overexpose until just before clipping. Even so, the camera's codec is too weak for CLOG imo. I had to use NeatVideo on a lot of stuff (it does pretty well at removing compression artefacts as well as noise)

These days I shoot WDR. I have done several tests between it and CLOG and found the difference in dynamic range to be almost negligible. I'd only use it in the most pressing circumstances where you really need to get those last drips of highlight detail - at the risk of problems in post. 

When exposing in WDR I find it sufficient to judge by how it looks on the LCD and by the exposure meter. Just expose to between 0 EV and 1 EV. Usually just works. I have not had any problems with this technique yet.

On the other hand, you might have a better experience than me with CLOG if you have an external recorder.