C300: how do I know I'm properly exposed when shooting in C-log

Just to clarify, I'm not suggesting you restrict the highlights to 62.74% IRE, it means that if you put a white piece of paper under the lighting where your subject will be standing you should read 62.74% which is only 2 stops over middle grey. Everything over that is dedicated to your highlights and will give you that nice subtle roll-off that everyone associates with "film like" characteristics.

There is always a bit of room to move but these are the "theoretical" values designed to give you the maximum benefit of the data used to represent the dynamic range across the entire sensor.

LOG is simply amazing when used right.
 
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using Lightmeter

using Lightmeter

I am a filmmaker coming from photography, reading all this technical stuff makes my ears drum.

Maybe I am being naive, but instead of reading the exact IRE settings every time, I decide to buy a Lightmeter and using that in a proper way should do the trick.

Using the indecent measuring outcome, will give me the F-stop that I will use. Because the outcome is based on the 18% rule I will allways be save (if there's not to much contrast in the lighting on the set, that is to say).

Based on the 'old photography rule' where there's only 5 stops latitude, 18% grey is in the middle of that, meaning it stays away 2 stops from detailled white.

I think it is save for me to use C-Log from now on and rely on the light meter (Sekonic L-758 Cine)
[h=3][/h]
 
lealain said:
I am a filmmaker coming from photography, reading all this technical stuff makes my ears drum.

Maybe I am being naive, but instead of reading the exact IRE settings every time, I decide to buy a Lightmeter and using that in a proper way should do the trick.

Using the indecent measuring outcome, will give me the F-stop that I will use. Because the outcome is based on the 18% rule I will allways be save (if there's not to much contrast in the lighting on the set, that is to say).

Based on the 'old photography rule' where there's only 5 stops latitude, 18% grey is in the middle of that, meaning it stays away 2 stops from detailled white.

I think it is save for me to use C-Log from now on and rely on the light meter (Sekonic L-758 Cine)
Click to expand...
Using a light meter is fine, but to be perfect you'll need to calibrate the meter to the camera and test the transmission of each lens you want to use, particularly if you are using stills lenses. Once calibrated you'll have more room to move in post if you use C-Log.
 
lealain said:
I am a filmmaker coming from photography, reading all this technical stuff makes my ears drum.

Maybe I am being naive, but instead of reading the exact IRE settings every time, I decide to buy a Lightmeter and using that in a proper way should do the trick.

Using the indecent measuring outcome, will give me the F-stop that I will use. Because the outcome is based on the 18% rule I will allways be save (if there's not to much contrast in the lighting on the set, that is to say).

Based on the 'old photography rule' where there's only 5 stops latitude, 18% grey is in the middle of that, meaning it stays away 2 stops from detailled white.

I think it is save for me to use C-Log from now on and rely on the light meter (Sekonic L-758 Cine)
[h=3][/h]
Click to expand...

The problem is that a light meter is set to expose 18% middle grey at 50%IRE. The remapped value of middle grey for C-LOG sits down around 33%.

So when working with C-LOG on Canon (or S-LOG on Sony, or LOG-C on Alexa, or Panlog with Panasonic) you can not expose middle grey this usual method or you will be over-exposing. You should always research the manufacturers specific remapped middle grey values, white and black values.

Take a look at the illustration on page 2 of this thread, I made a quick reference chart for C-LOG. You can see that middle grey should be down more around 32.79% IRE and a white card would be 2.25 stops over that and sitting around 63%IRE.

I will say it again, middle grey is 33%IRE in C-LOG mode not 50%IRE.
 
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I had to jump in here. starcentral is correct to say that C-LOG middle grey is 33%IRE and not 50%. But 18% middle grey is 18%. If you lightmeter reads 5.6 at middle grey then it's 5.6 for C-log. Quick way to see it is to set the camera profile to EOS Standard and get the light meter reading for middle grey. It will read 50%IRE on the camera waveform. Then switch the profiie to C-LOG and the waveform will drop in value to 33%IRE for middle grey. For C-LOG you just has to remember it's like it readdressing values. But if all you have is a the camera waveform then you better know that 33%IRE is middle grey for C-LOG.

I don't got all this throwing out basic exposure. It the same as it was before. A light meters has been used by cinematographer for ages.
 
shoot_me_silly said:
Quick way to see it is to set the camera profile to EOS Standard and get the light meter reading for middle grey. It will read 50%IRE on the camera waveform. Then switch the profiie to C-LOG and the waveform will drop in value to 33%IRE for middle grey.
Click to expand...

Yeah, that ain't happenin'. You set your profile and leave it, calibrate your tools for Log. There's too much possibility of error doing this kind of thing on a busy, hectic set.
 
starcentral said:
The problem is that a light meter is set to expose 18% middle grey at 50%IRE. The remapped value of middle grey for C-LOG sits down around 33%.
Click to expand...

No, this is not correct.

A light meter doesn't care about IRE. It measures a standard exposure for 18% gray, based on the known variables: aperture, ISO, shutter speed (or frame rate if you use that).

Where on the IRE scale that 18% gray value falls is up to your chosen gamma curve. For Canon Log it's just shy of IRE 33.

If you meter a scene and expose according to your meter, that is what you will get in Log mode. If you leave the exposure as it is and just change picture profile you will see that the gray value jumps up to maybe 50%, for the EOS profile for example. Your gamma curve maps the gray value.

Documentation surrounding the Log profile even states that it had external light metering in mind when it was developed. Just like it anticipates a post production workflow.

-------------------

EDIT: others were faster, I see....
 
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I never suggested to do this during a shoot. This is homework you before get on set. Test the camera out understand how to exposure properly for whatever a,b,c,d-log your using. How hard is it to remember 33%IRE on the waveform is 18% middle grey for C_LOG. Hell put a big ass sticker on the camera if that helps. whatever works.
 
shoot_me_silly said:
I had to jump in here. starcentral is correct to say that C-LOG middle grey is 33%IRE and not 50%. But 18% middle grey is 18%. If you lightmeter reads 5.6 at middle grey then it's 5.6 for C-log.
Click to expand...

Correct.

shoot_me_silly said:
I don't got all this throwing out basic exposure. It the same as it was before. A light meters has been used by cinematographer for ages.
Click to expand...
The problem is lenses. Specifically, the stills lenses that most people are using - they are not marked in T-stops and exposure varies between lenses at the same f/stop. Zoom lenses can vary transmission at different focal lengths on the same lens, even with a constant aperture.
 
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