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View Full Version : ETTR, how do you see anything on the screen?



iunknown
02-08-2013, 08:14 PM
When I expose to 100% zebras I can't see anything. Are people using external monitors to do this? Do the luts you load onto the external monitors allow to set the exposure -2 so you can see what you are shooting?

John Brawley
02-08-2013, 10:30 PM
When I expose to 100% zebras I can't see anything. Are people using external monitors to do this? Do the luts you load onto the external monitors allow to set the exposure -2 so you can see what you are shooting?

If you're shooting RAW, just use the ISO and set it to 200 or 400.

jb

EDIT. This has no effect on how the Zebra's respond, which are ISO independent....

iunknown
02-08-2013, 10:36 PM
Haha, thanks John. Man I'm a newb.

jambredz
02-09-2013, 11:13 AM
And if not shooting raw?

John Brawley
02-09-2013, 05:59 PM
It's more difficult. Because when you lower the ISO in ProRes, you will sacrifice some DR.

Remembering this is a work around to ETTR that causes the LCD screen to be very bright. It's bright, especially in VIDEO because you're overexposing it. Another solution is to switch to FILM monitoring. Then you'll see everything, but sort of washed out....

jb

dcloud
02-09-2013, 06:27 PM
so far on my case, i use a fader or ND filter and set the ISO to 800. no ways getting around it on prores. you shoot like any normal camcorder. so an external monitor would defnitely help.

teh
02-10-2013, 02:26 PM
I pretty sure this was discussed before but what the best way to get you exposure right when shooting prores? Setting zebras at 100 like in Raw?

iunknown
02-16-2013, 06:50 PM
John, did some more testing with this today. The thing I don't get, if ISO is just metadata, then why does my clipping point when I change to 800? I expose for 200 iso, and see no zebras, but when I change it to 800, I see zebras??? Halsu thread below also seems like something changes in ISO 200 and 400:

http://www.bmcuser.com/showthread.php?2314-My-Frustrations-with-BMCC-so-far-You-should-also-brace-yourselves-for-a-change&p=49995#post49995

I did some test of my own and don't see the clipping in the blue and green channel like he is, but the change in Zebras tells me its not just metadata?

John Brawley
02-16-2013, 06:53 PM
John, did some more testing with this today. The thing I don't get, if ISO is just metadata, then why does my clipping point when I change to 800? I expose for 200 iso, and see no zebras, but when I change it to 800, I see zebras??? Halsu thread below also seems like something changes in ISO 200 and 400:

http://www.bmcuser.com/showthread.php?2314-My-Frustrations-with-BMCC-so-far-You-should-also-brace-yourselves-for-a-change&p=49995#post49995

I did some test of my own and don't see the clipping in the blue and green channel like he is, but the change in Zebras tells me its not just metadata?


I haven't looked for a while but you should find that with Zebra's at 100%, the clipping point won't change as you change ISO.

Are you set at 100% ? The curve is changing, so something near clipping might bend and stretch as you get closer to clipping. So Zebras at 90% might see changes for example.

jb

iunknown
02-16-2013, 06:58 PM
Yeah, set at 100%. Anyone else seeing the same thing? John, what do you think of Halsu's post? It doesn't look like a resolve interface? Thanks for all your help with this stuff, btw.

Andrew
02-16-2013, 08:11 PM
Yeah, set at 100%. Anyone else seeing the same thing? John, what do you think of Halsu's post? It doesn't look like a resolve interface? Thanks for all your help with this stuff, btw.

I've experienced this. At one iso the zebras were peaking at 100% and at another iso they weren't. This is part of the reason I started setting my highlights a bit lower. I'm not sure what it means, but I'd love to find out.

John Brawley
02-17-2013, 07:30 AM
John, did some more testing with this today. The thing I don't get, if ISO is just metadata, then why does my clipping point when I change to 800? I expose for 200 iso, and see no zebras, but when I change it to 800, I see zebras??? Halsu thread below also seems like something changes in ISO 200 and 400:

http://www.bmcuser.com/showthread.php?2314-My-Frustrations-with-BMCC-so-far-You-should-also-brace-yourselves-for-a-change&p=49995#post49995

I did some test of my own and don't see the clipping in the blue and green channel like he is, but the change in Zebras tells me its not just metadata?

So there are four ISO settings in the BMCC.

What's happening, even in DNG, is that the camera takes the image from the sensor at GREATER than 16 bit, and converts it into a 16 bit linear file. Then for DNG encoding it converts it to 12 bit LOG. For each ISO, BMD have designed a CURVE that is embedded in the DNG header as a kind of reference to the application that opens it.

BMD have designed each of the curves at 200, 400 and 800 to be close, but there are really small differences. Bear in mind, this is the CURVE that's applied, not what the actual linear 16 bit data is. This is a starting point for the imaging application. BUT, you don't have to sue that curve. Using the application, if it accesses the source file, then you're basically starting from the same point. And yes, it's basically always ISO 800.

Now, with ISO 1600, there is a small difference in the DNG file. It does in fact clip a tiny little bit earlier, and I believe it does this because it puts more of the bits in the shadows, presuming you want more precision in the bottom end. So you have the same DR, but it's now slightly biased towards shadows a bit more.

The zebras are still accurate, so 100% zebra clipping still represents the slightly reduced clipping point.

These are very small differences we're talking about.

And my understanding is that the 100% zebra is always showing sensor clipping, and that shouldn't change except that at ISO1600, there may b a little more.

jb