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Old March 14th, 2012, 08:27 PM   #1
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Is exposing C-log different than usual?

Since I'll be shooting with a C300 in 2 days from now I wonder whether there are different rules than usual when I use C-log instead of a normal colorprofile.

What is the right way to use (and expose) C-Log?

And is grading different too or not?
(I usually use Colorista and Magic Bullet Looks (not just the presets) to grade my EX1R-footage while using waveforms.)
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Old March 15th, 2012, 12:36 PM   #2
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Re: Is exposing C-log different than usual?

Yes. When shooting log you have to consider that in order to record the increases dynamic range, each stop of exposure is allocated a very similar amount of data. But as each extra stop is a doubling of brightness range there is in effect more and more image compression occurring as the image brightness increases. For maximum grade ability, you don't want all your picture information up in the highlights. So generally with a log curve you will underexpose slightly compared to a standard gamma. The norm is to use a mid grey card and expose it so that it is at 38% and reflected white should be somewhere around 70%. Reflected white at 70% then allows headroom for direct light sources like the sky or reflections off shiny surfaces.

That's the theory at least, in practice things will vary from scene to scene, but the primary concern is to not overexpose and to keep highlights well controlled.
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Old March 15th, 2012, 01:10 PM   #3
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Re: Is exposing C-log different than usual?

I'd also like to hear form others on this. I hear you on the grey/white card method but is there an easier way to get perfect exposure on the fly without a card in the scene? On the EX1, I set zebra 1 to 56 IRE and exposed for zebras on the brightest part of the subject's face (except dark skin people) and the results were always great. But you can't do that with the current C300 firmware. And I also don't like how zebra 1 & 2 look so similar. On the EX1, zebra 2 was much thicker which was fine because that was overexposed anyway.
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Old March 15th, 2012, 01:33 PM   #4
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Re: Is exposing C-log different than usual?

Quote:
Originally Posted by Alister Chapman View Post
Yes. When shooting log you have to consider that in order to record the increases dynamic range, each stop of exposure is allocated a very similar amount of data. But as each extra stop is a doubling of brightness range there is in effect more and more image compression occurring as the image brightness increases. For maximum grade ability, you don't want all your picture information up in the highlights. So generally with a log curve you will underexpose slightly compared to a standard gamma. The norm is to use a mid grey card and expose it so that it is at 38% and reflected white should be somewhere around 70%. Reflected white at 70% then allows headroom for direct light sources like the sky or reflections off shiny surfaces.

That's the theory at least, in practice things will vary from scene to scene, but the primary concern is to not overexpose and to keep highlights well controlled.
That's a great summarization. Cheers, Alister.
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Old March 15th, 2012, 03:14 PM   #5
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Re: Is exposing C-log different than usual?

56 IRE for skin tones with standard gamma? That's quite low for a standard gamma, it's more common to use 65 IRE for skin tones. Is that a typo?

With C-log, skin tones I would place bright skin tones around 60IRE.
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Old March 15th, 2012, 05:53 PM   #6
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Re: Is exposing C-log different than usual?

Nope not a typo. I got that number from an unusual source. It's what Marshall recommends for skin tones when using their false color feature. Looked great to me so I stuck with it.

So 60 in C-Log sounds good to me. Except the C300 only goes down to 70. :-/

Edit: 70 on zebras that is

Last edited by Graham King; March 15th, 2012 at 08:11 PM.
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Old March 15th, 2012, 07:07 PM   #7
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Re: Is exposing C-log different than usual?

Thanks for the quick and helpfull replies!

Since I'll be on a very tight schedule, I'm considering using a normal gamma instead of C-log.
(Practising C-log exposure has to wait, I guess ;-) )
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Old March 15th, 2012, 11:15 PM   #8
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Re: Is exposing C-log different than usual?

i really do hope canon updates firmware so we can get zebras below 70
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Old March 17th, 2012, 09:39 AM   #9
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Re: Is exposing C-log different than usual?

I've emailed pro support up here in Canada about the zebras under 70, and was told it would be forwarded to the correct people. Probably a good idea for everyone to do the same in their region.

Also brought up having selectable display of the SDI. For example only sending TC to the client monitor, instead of everything on the screen.
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Old March 17th, 2012, 06:14 PM   #10
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Re: Is exposing C-log different than usual?

yeah,

i keep calling about once a week asking for a few things...most of them correctable with firmware.

I also really want them to make it so that when you split one source of audio to both channels, you can control the levels of the 2 channels seperately.

as it is now, when you split the one source the two channels are locked at the same volume.
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Old March 18th, 2012, 02:10 AM   #11
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Re: Is exposing C-log different than usual?

I can't seem to assign two different functions to the wheel on the hand grip and the lower wheel on the body. Has anyone been able to do this? I would request that in a firmware update if it's not currently possible.
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Old March 18th, 2012, 10:26 PM   #12
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Re: Is exposing C-log different than usual?

yes, thaat is my other request. i want to have iris on handle and ISO on the body
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Old March 18th, 2012, 10:28 PM   #13
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Re: Is exposing C-log different than usual?

That's exactly what I wanted to do!
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Old March 19th, 2012, 09:05 AM   #14
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Re: Is exposing C-log different than usual?

yup....would probably save me an hour over the space of a year...
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Old March 19th, 2012, 11:02 AM   #15
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Re: Is exposing C-log different than usual?

I assigned ISO to button 1 so I can't say it'd save me an hour per year but it would be nice. Actually, if it could be assigned to color temp I'd probably do that as I do a lot of run & gun.
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