C100: WDR or Canon Log

Dino said:
With C-Log, you expose reflected whites at 70%, therefore 30 units of highlight protection. Wide DR puts reflected whites at 80% or 20 units of highlight protection, assuming 18% gray card exposed at 40% for both. REC709(Norm gamma)would be more like 90-95% whites, offering little highlight protection.

C-Log has more tonality in highlights than WDR, flesh should not be higher than 50%, or there will be loss of tonality in the skin tone due to compression in the mids.
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Yikes! So do you meter the two differently?

By "units" do you mean IRE? Because the camera seems to go to 109... and at a given ISO highlights clip at the same point, indicating the same +/- for Canon Log and WDR, despite different distribution of tonality.

I am somewhat confused. Usually just shoot Canon Log and meter as I would were I shooting film, check the WFM for clipping.
 
Most cameras have a hard clip point of 109 IRE(or 100), this has nothing to do with gamma, knee or slope settings. The gamma curve is how the dark to bright areas are allotted. If there was a linear gamma, each f-stop would represent the same amount of units, but gamma curves aren't linear, thus "Log" for logarithmic.

When a Cine gamma is chosen instead of REC 709, mids and mid-blacks will be compressed more than the whites, the camera will lose sensitivity, although this can be brought back in grading.

I don't use a meter these days since cameras have scopes built into them. A scope and an 18% gray card are good for reference points. Obviously you can meter off of the card as well. If a gray card isn't practical, use reflected whites or skin tones as a reference.

I would recommend against always exposing to avoid clipping, this could put mid blacks and mids too far into the mud in very high contrast scenes, too far to retrieve with an 8-bit codec without adding a lot of noise and banding. Conversely, if there aren't highlights in the scene, don't raise the exposure just to fill the waveform, this will negate the advantage of film or log gammas.
 
Dino said:
I would recommend against always exposing to avoid clipping, this could put mid blacks and mids too far into the mud in very high contrast scenes, too far to retrieve with an 8-bit codec without adding a lot of noise and banding. Conversely, if there aren't highlights in the scene, don't raise the exposure just to fill the waveform, this will negate the advantage of film or log gammas.
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This.
 
I'm not asking a complicated question, but I keep getting complicated answers.

At a given ISO ≥850, do WDR and Canon Log have the same +/- if exposed at the same stop/shutter speed?

I am old school... unless it's event videography, I meter. Never said I exposed to avoid clipping, just that I use the WFM instead of a spot meter to check where highlights clip, though of course still use the spot meter while lighting before camera is set if trying to blow out a window or something. Don't need didactic video 101 advice... asking a simple question here: if I meter traditionally (using an incident meter, not WFM), do WDR and Canon Log have the same +/-?

I ended up using the Ninja when convenient. Just hate the form factor, turns a small camera that fits anywhere into an awkwardly shaped one. AVCHD seems fine tbh.
 
From another post, showing that at a given IRE level, different gammas require different f-stops:

So differences in exposure are very dependent upon gamma, especially very nonlinear gammas like log, as well as resolution, shutter and frame rate. Here are examples of f-stop vs. IRE with three different gammas: (the values are only valid relative to each other)


C-Log


f4 = 50IRE
f5.6 = 38
f5.6 1/3 = 32


Norm 1


f5.6 = 50
f5.6-8 = 38
f8 = 32


Wide DR


4 2/3 = 50
5.6 = 38
5.6 2/3 = 32


Policar, so yes, different gammas mean different stops for the same value, you cannot meter them the same. Sorry if my responses were too Video 101 or didactic, I am not just posting for your benefit alone. There are some members who need a bit of Video 101 refreshers from time to time. The hard clip has no bearing on where you place 18% gray, which was a theme you kept coming back to.
 
Policar said:
....Why does WDR at 320ISO clip the same as log at 850ISO? What about 850 vs 850?
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Output from the chip is the same (in the case of the same exposure).
C100/C300 has the gain/iso amplifier before A/D converter at the analogue domain.

For the same exposure of the chip: If you set canon log with 850iso (+2.5dB) then it has 800pct DR (72dB)
If you will change gamma to cine1 (cine1 gamma has 300pct DR), you will lost 72-63.5=8.5dB of the DR.
But if you will change iso from 850 (+2.5dB) to 320 (-6dB) then you will get exactly +8.5dB for the white peak (before A/D conversion).

Try this with WF monitor on and you will see. But at evening is the change from 850iso to 320iso to much for correct exposure,
at the day it is ok.

edit: 709 gamma (normal3 for Europe) with knee has also 300pct DR then you will get the same result as with cine1 gamma.
 
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Shooting in a totally controlled studio environment, should "average" caucasian skin be exposed ~70% on the waveform monitor using "stock WDR" on the C100? If, not, where and why? Thanks.
 
I would shoot them at 60-65% on video (less in cine) because of the issues of tonal compression on the WDR gamma curve. There seems to be a temptation driven by web based video for 'lighter skintones' - and don't let me get started on the C100's lack of zebras below 70IRE. ;-)
 
Thanks. Anybody want to weigh in on how to accomplish 60-65% on "average" caucasian skin with zebra bottoming out at 70%?
 
Dino said:
Most cameras have a hard clip point of 109 IRE(or 100), this has nothing to do with gamma, knee or slope settings. The gamma curve is how the dark to bright areas are allotted. If there was a linear gamma, each f-stop would represent the same amount of units, but gamma curves aren't linear, thus "Log" for logarithmic.

When a Cine gamma is chosen instead of REC 709, mids and mid-blacks will be compressed more than the whites, the camera will lose sensitivity, although this can be brought back in grading.

I don't use a meter these days since cameras have scopes built into them. A scope and an 18% gray card are good for reference points. Obviously you can meter off of the card as well. If a gray card isn't practical, use reflecte

I would recommend against always exposing to avoid clipping, this could put mid blacks and mids too far into the mud in very high contrast scenes, too far to retrieve with an 8-bit codec without adding a lot of noise and banding. Conversely, if there aren't highlights in the scene, don't raise the exposure just to fill the waveform, this will negate the advantage of film or log gammas.
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I don't agree on the ETTR note, just from trying with my own eyes. Exposing to the highest value just below clipping, gets me the cleanest image with the most DR. If my exposure is any less, then I am not gaining anything in the highlights, but just increasing the noise floor, therefore decreasing DR.

I've never had any kind of codec break up when lowering down the waveform, not even with the C100 internal codec (or DSLRs codecs), in fact, the only codec issues I get is when I don't expose to the right and try to bring the WFM UP, That's where the ugliness happens.

From my experience, the best way to get the highest quality image is to Expose to the right, and then adjust in post, this even affects the colour quality and saturation and especially the shadow noise, just a clearly better image from my tests. I've found this results identical in every single camera I've tested, so now I just use it as my main exposure technique, it's true on all Canon/Nikon DSLRs, GH4, A7s Slog2, C100 Clog, C300 Clog, and even alexa.

I would only expose "correctly" with skin at 70IRE etc if I am delivering without grading at all.

Because the results in my tests were too obvious and significant, I am quite doubting myself as MANY pro cinematographers don't expose that way, so I Would love to see other people's tests if you find otherwise, I'll post mine here in a little while.
 
Some old tests I dug out on Exposure.

ETTR Log ungraded
OswTu6H.jpg


"Correct exposure or slightly under" Log ungraded
mS6IHih.jpg


ETTR corrected to match the correctly exposed
3GeRhnJ.jpg


ETTR
V3CvzlK.jpg


Correctly exposed
VyT3ubn.jpg


ETTR to correct exposure
2lTKnIU.jpg


As shown no problems at all occur when pulling to ETTR to correct using a heavily compressed 8bit codec, I even end up with much better quality that way.

I mean it's such a huge difference in image quality that I never expose correctly or slightly under anymore, the higher you go in exposure and the more you feed the sensor light the better quality, thicker colour, less noise and more DR you get, to my eyes anyway.

What do you guys think, anyway having the same results with ETTR? It's even giving me perfectly clean images at 10.000 ISO that I would never get exposing correctly.
 
In my experience, let's say the brightest part of an image is a person's face, so if you expose their face at the top of the waveform, around 95 IRE, then bring it down to say 65-70 IRE in post, the image looks desaturated (in the sense where you can't bring the color back properly), washed out, etc. It will be clean, yes, but it will look bad. I almost always shoot in Wide DR, so I mean when using Wide DR.
 
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