C100: Just got a C100. C-Log is a tricky little beast.

G

gh4_storyteller

Active member
Heyo! This is my first post in the Canon Cinema EOS corner of DVXUser. I just recently switched from the Panasonic GH4 to the C100 since my projects increased in volume; and I needed a workhorse over 4K.

I've been super excited about using C-Log on the C100, and yesterday I went out to get some test shots. From what I understand, C-Log intentionally under-exposes the image in an attempt to squeeze as much out of the highlight's as possible. Which in theory, is fine. The camera shoots middle grey at 32 IRE, so midtones simply need to be brought back up to 50 to put the image back at normal exposure. Then the whites or the over-exposed part of the image is brought up or down to sit right at 100 IRE. Last blacks are brought down to 0 IRE and now you have a proper exposure-corrected image. However, on the internal codec, that amount of post work is pushing the codec beyond what it can handle. I think that C-Log is maybe attempting to retain too much information for it's own good.

I'm assuming the only real way to fix this is to expose the image a little brighter than what Canon suggests, but I hate that I'm waisting a few stops of light to simply go around what the C-Log is doing.

I'm not trying to find a definitive answer on how I should expose; I just really want to know what you guys are doing and how you're exposing when shooting C-Log on the internal codec.
 
I shoot WDR unless I am specifically ask to shoot LOG. I find the C100 files do much better in post if you don't have to push them too far. The WDR profile gives you the best of both worlds and is easier to focus and expose. Exposure for LOG is a totally different animal. Use the waveform and expose highlights for 60-65 IRE if you must shoot LOG.
 
This is why external recorders have been so successful with the C100: Atomos Ninja 2/Blade/Star, et al.
The internal AVCHD is great but there's only so far that you can push it.
 
Try ETTR, just try it once and see how the images look. You'll be pleasantly surprised. Just remember, don't clip your highlights, expose to the point just before that.

The C100 images come to life when brought DOWN while die when pushed UP, and non-raw camera for that matter as far as my experience goes, very very little video images like being pushed up any amount.

Forget about theory and numbers and just do a couple of tests, little under Canon's suggested, at suggested, and ETTR. Ingest the three, push them around and see what you like best. I bet you it's the ETTR ones.
 
Daniel Brown said:
Heyo! This is my first post in the Canon Cinema EOS corner of DVXUser. I just recently switched from the Panasonic GH4 to the C100 since my projects increased in volume; and I needed a workhorse over 4K.

I've been super excited about using C-Log on the C100, and yesterday I went out to get some test shots. From what I understand, C-Log intentionally under-exposes the image in an attempt to squeeze as much out of the highlight's as possible. Which in theory, is fine. The camera shoots middle grey at 32 IRE, so midtones simply need to be brought back up to 50 to put the image back at normal exposure. Then the whites or the over-exposed part of the image is brought up or down to sit right at 100 IRE. Last blacks are brought down to 0 IRE and now you have a proper exposure-corrected image. However, on the internal codec, that amount of post work is pushing the codec beyond what it can handle. I think that C-Log is maybe attempting to retain too much information for it's own good.

I'm assuming the only real way to fix this is to expose the image a little brighter than what Canon suggests, but I hate that I'm waisting a few stops of light to simply go around what the C-Log is doing.

I'm not trying to find a definitive answer on how I should expose; I just really want to know what you guys are doing and how you're exposing when shooting C-Log on the internal codec.
Click to expand...

Placing 18% gray (middle gray) at 50 IRE is wrong, contrary to popular opinion. 38-40 IRE is a pretty standard place for it to end up. 32IRE is dark, however, yes.

I expose as I normally would, metering with my 758 cine. But I mostly shoot WideDR.
 
I consider myself a pretty smart, pretty good videographer/editor, but I can not make pleasing images out of internal LOG files from the C100. I'll have to try the ETTR method described above.
 
I find c-log quite odd to work with as well. It's nowhere near as flat as BMDFilm and doesn't really feel like a 'true' log format. When I bought the C100 I was hoping for a log format similar to what Blackmagic uses.

Saying that I did shoot an entire promo video in log which I was happy with. I used the waveform and made sure I wasn't clipping highlights. I did find shooting people quite difficult as I wasn't sure where to place them on the waveform. Usually I try and get white skin tones around 70IRE on the waveform but I didn't know where to place them in log. I'm not entirely convinced shooting log on the internal codec is a great option to be honest.

I have since bought a Atomos Ninja Star but I haven't shot any log projects using that yet, only WDR. I'm very interested to try c-log recorded to ProRes 422 and HQ.

I think my main issue with c-log is that it doesn't appear to be a flat enough image to make the extra post worthwhile. I know when shooting BMDFilm with my BMCC I can get away with murder but not with c-log.
 
Last edited:
By the way, for those who didn't know what ETTR was (like me), it's "exposing to the right." https://en.wikipedia.org/wiki/Exposing_to_the_right I've actually been doing this all along on the C100, as well as on other cameras I've used in the past, and I agree it's a better method, especially with C-log.

In my six months or so of experience shooting with the C100, I've discovered that any significant post work with the internal codec is hit or miss, even if you're bringing things down in post. I prefer to shoot ProRes on an external recorder, unless I'm piddling around.
 
Shane Hurlbut's tests have found that 55-60 IRE is the sweet spot for skintones when shooting C-LOG. Canon suggested under 40 and he ended up with very underexposed images when he shot need for speed. I've been sticking to that and have been very happy with the results.
 
Humanoid Typhoon said:
Shane Hurlbut's tests have found that 55-60 IRE is the sweet spot for skintones when shooting C-LOG. Canon suggested under 40 and he ended up with very underexposed images when he shot need for speed. I've been sticking to that and have been very happy with the results.
Click to expand...

I would have assumed this would lead to slightly under-exposed footage. I'll have to try some tests at 55-60 IRE
 
I expose skin at around 50-55 and it works great.

FWIW, I think the internal codec can handle C-LOG just fine. It's just the finer details that will benefit from an external recorder. I use an external recorder 99% of the time.
 
ryanhargrave said:
I expose skin at around 50-55 and it works great.

FWIW, I think the internal codec can handle C-LOG just fine. It's just the finer details that will benefit from an external recorder. I use an external recorder 99% of the time.
Click to expand...

I shot a short promo in c-log internally and Resolve really did not like the codec, it kept freezing and struggled to playback the clips. It handles RAW better. I ended up converting it all to ProRes LT (using Cinec) and bought a Ninja Star.

The C100 internal codec is really impressive in terms of the huge amount of detail it squeezes into 24bmps. Unfortunately it doesn't play very nicely in Resolve, VLC and other software.

I just shoot ProRes LT now purely for a smoother post. It's also easier to hand an editor 25p ProRes LT rather than 25PsF AVCHD.
 
Ive been using the C300 (its still log with 12 stops) since first week of release and I immediately found the canon recommendations for exposure were too low. When I want the perfect skin tone / exposure, I've always used 50 ire. If anyone out there is using an L758 cine - thats ETTR by about a stop.
 
Need to second Humanoid Typhoon's comment regarding C-LOG. I had previously followed the recommendation to set middle grey at 32 IRE (I think, Jem Schofield's YouTube tutorial suggests this), and had major problems in post even when outputting directly to ProRes 422. To quote Shane Hurlburt directly from his article "CANON C100 MARK II - The DSLR Killer - Extensive Tests" he writes: 1) 50 IRE on a Grey Card, 2) I would go with C-LOG. Not a fan of WDR.
 
You must log in or register to reply here.
Back
Top