C100: C100, C log, noise and exposure

Y

Yoyodyne

Active member
So got my hands on a C100 for the weekend and shot a little "test" focusing on c-log. Test is probably being way to generous, just me grabbing a few shots over the Superbowl weekend playing with the camera.

Here is the vid:

https://vimeo.com/59020760

I was mainly concerned with exposure and noise. Exposure with the Canon C log has been a bit tricky for me it seems. The rule of thumb seems to be to expose middle grey (18% grey) at around 35% on the waveform. Here is an exerpt from Dennis Hingsberg on his blog where he explains:

"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."

The article is here and it's a great read:

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

The issue I'm running into is noise when grading all that "under exposed" footage back to normal. I'm all for protecting highlights but I'm trying to find the sweet spot between max dynamic range and lowest possible noise. I'm also experimenting with shooting flat in very low contrast environments and see how the C100 handles it. Technicolor Cinestyle on the 7D can get real noisy in low contrast environments and I was curious to see what the C100 would do.

I was having pretty good luck exposing a lot of the low contrast shots up to about 80%IRE for the brightest areas. This seemed to keep the middle part of the range in the exposure/noise sweet spot and I could play with the shadows and highs at will in post without introducing noise. In the higher contrast shots I was trying to protect the highlights as much as possible while not letting the bulk of the image get too dark. In grading I was finding a bit of noise was coming up with the dark-middle regions so I applied Neat Video and that really cleaned it up.

So I was wondering, how are other folks working with C log? Any tips, tricks or anecdotes?


Oh and just FYI, all the shots where C log (except one I think) with ISOs between 850-3200. Used a Tiffen Polarizer on most of the shots. Lenses were a Canon 50mm f1.4, Canon 35mm f2, and a Tokina 11-16 f2.8.
 
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OK first off, some lovely shots in there. The math on the 18% grey isnt wrong, just how its applied and then reworked in post.

First question, how did you determine middle grey for each shot? Visual guestimation? That can be tricky the first few times you pick up any of the EOS C cameras - so further use you could expect that to go away.

In a perfect world we'd go out and shoot and all contrast would sit in our happy 12 stop range. In controlled lighting thats what we would be doing. Sometimes we go out and the contrast is very high - a shadowed something with sun and clouds in background. Like any camera theres no 1 way to lay the contrast down - get enough of the shadow? expose to protect the highlights? Sometimes you're just going to have to 50/50 those when you have no light control, or choose another time of day to get the shot etc for the best result. Yes, 18% grey at around 35 ire is the rule of thumb, but if to protect the highlights means your blacks are 7 or 8 stops under 18% grey to do it, you need to rethink the shot as you'll most likely be carrying some noise in the darker areas and you're going to be crushing things too much into the lower end.

Also, the method to "retime" / "delog" the image becomes very important. I've found that bringing up overall exposure and then pulling your blacks back down is a reasonable approach to this. You can then tweak a little with some additional mids, or deduction in whites as your start point.
 
Thanks for the response Noel!

This was graded with Colorista 2. I'm still trying to come up with a "best practices". Maybe I've watched to many tutorials :) I was basing my grading workflow on this post by VASHI NEDOMANSKY who is basing his workflow on Stu Maschwitz’s advice:

http://www.hurlbutvisuals.com/blog/2012/01/7-tips-for-hd-color-correction-and-dslr-color-correction/

he sums it up with this:

"TIP #3 – ORDER OF OPERATIONS
To maintain image quality and to preserve as much info as possible, it’s important to do things in the proper order. Just as you wouldn’t ice a cake before you bake it, when you apply an effect is critical. I have always achieved great results using Stu Maschwitz’s advice. Doing Color Correction on your footage in this order will help you maintain extremely high quality in the interaction of all the effects you use. Not all steps are needed for every shot but in case you have to use them all, here they are:

1. Remove artifacts and de-noise.
2. Balance your shots by adjusting BLACKS/MIDS/WHITES, SATURATION and WHITE BALANCE.
3. Relight within a shot using power windows or masks.
4. Add gradients, diffusion and other lens filters.
5. Add vignettes
6. Grade your images
7. Simulate a film stock of your choice
8. Resize and sharpen


Noel, what tool/s do you use to grade? Would love a quick detailed-ish peak at your workflow.

Concerning de-logging - I've installed LUT Buddy from Red Giant but for the life of me can't find a LUT to delog C log for the C100. Would love to try this as a handy grading reference but I must be missing it. I tried the Canon web site, I can find one for the C300 but it just seems to be a text file. If anyone knows where the C100 LUT is hidden please let me know :)
 
Lets start with the LUT's you're looking for. My advice forget them - unless you can get a LUT that pertains exactly to the piece / lighting and style your shooting. Then its great for rushes. Problem with LUTs is they don't know the set conditions, you may have had to pull your exposure up / down a little from norm - the LUT will just crash those values based on a set of numbers. When talking narrative or TVC, I'll do some test shooting and create a base look within FCPX, then if I need to I can use that as a faux LUT base for rushes.

From there I use Davinci Resolve. Those order of operations are very similar to how Id go about it. Although I dont often need to use NR.

The log file for C300 log and C100 should be the same. What NLE are you using?
 
I'm editing in Adobe Premiere CS 5.5 and using Magic Bullet suite for grading. Mostly Colorista II unless I'm going for a more extreme look and then I throw it in Magic Bullet looks. I'll often use Cosmo to smooth out faces and I'm often adding sharpening using the Adobe unsharp mask. I find that the regular Adobe sharpening tool tends to increase noise too often - unsharp mask has been more reliable.
 
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