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zwarte_kat
03-20-2013, 10:08 AM
Dear all,

I have an Ikan SDI monitor with waveforms, which works nice with the BMC.
With Prores video mode, I can image it's the same as any other camera that doesn't shoot raw, but what about prores film or RAW?

I heard about exposing to the right on the BMC many times, would you expose as much to the right as possible without crushing highlights? Where would yo try to position other things like skin tones and dark/black backgrounds? Anything else you'd be doing differently wit RAW?

In which area in the waveform monitor whould you try to get most of your image?
And any useful links in general?

Cheers!

razz16mm
03-20-2013, 02:49 PM
Exposing to the right refers to the use of a histogram rather than waveform monitor. Not sure how the waveform would align with raw, probably just gives SDI video level values from the monitor path. But the general idea is to get as much exposure as possible without exceeding 100 IRE max white level on the waveform. Watch your zebras for raw clipping.

Frank Glencairn
03-20-2013, 06:49 PM
I don't know how they did it, but the waveform of my monitor correlates pretty good with 100% Zebra.

And yeah, forget the idea to put something on some level while shooting - it's meant do be done in post.
You just want to feed the sensor as much light as possible without clipping, to keep low noise in the shadows.

zwarte_kat
03-21-2013, 12:31 AM
Exposing to the right refers to the use of a histogram rather than waveform monitor.

Haha you are right, maybe I should have said "Expose to the up"!

Anyway thanks for the answers guys.I heard that the shadows can be a bit noisy when underexposing, so will be keeping those in check. In a wildly contrasty situation I'd rather end up with a few blown out highlights than noisy dark tones.

What I now often do, is push the iris button with an active EF lens, and then increase the aperture to see what gets blown out (lightsources, for example). It's just that I have no clear way to see where the blacks are at. Well unless I have this monitor, which I really like for both of my FS100 and BMC.

In terms of lighting, Is the image more flexibly to grade if I made the scene (lighting) contrastier, filling up all the DR the cam offers, or should I leave that up to the post process? Not talking about a look, just in general.

razz16mm
03-21-2013, 07:50 AM
Haha you are right, maybe I should have said "Expose to the up"!

Anyway thanks for the answers guys.I heard that the shadows can be a bit noisy when underexposing, so will be keeping those in check. In a wildly contrasty situation I'd rather end up with a few blown out highlights than noisy dark tones.

What I now often do, is push the iris button with an active EF lens, and then increase the aperture to see what gets blown out (lightsources, for example). It's just that I have no clear way to see where the blacks are at. Well unless I have this monitor, which I really like for both of my FS100 and BMC.

In terms of lighting, Is the image more flexibly to grade if I made the scene (lighting) contrastier, filling up all the DR the cam offers, or should I leave that up to the post process? Not talking about a look, just in general.

If it is possible to exercise some control over scene illumination, keeping scene contrast ratios well within the camera's range works best. Even in outdoor sun you can use low con filters or silks to cut highlights and reflectors to fill shadows. Doesn't have to be expensive. I have used 4x8 foot $6 sheets of white foam core to make very large reflector panels. It is much easier to add contrast in post than to compensate for clipped highlights or noisy shadows from contrast ratios wider than the camera can handle.

Ryan Walters thought the usable DR of the BMCC was around 10 stops from his tests. Controlling light ratios to stay within 8 to 10 stops if possible will produce cleaner images. This is where an incident light meter is most useful.

PaulDelVecchio
03-21-2013, 02:51 PM
The problem with just saying "expose to the right and give the camera as much light as possible without clipping" is that maybe that will work for outdoors, but if you're lighting a scene with shadows, for example a basement scene with pools of lights and shadows, you cannot just throw up a key light and some fill and fix the lighting in post. You have to be aware of contrast ratios and what the scene looks like when brought back down. That's why I typically set the ASA to 200 or 400 and view in VIDEO mode so I can get an idea of what the contrast ratios are between dark, skintones, and light areas. Bringing the shadows up on set makes them less noisy, but if you go to far, the overall light design might be ruined. I'd switch back and forth between 200, 400, and 800 ASA in order to see what I'm capturing and what it could look like in post. I've noticed that 200 ASA in VIDEO mode is a little far. It's very contrasty and a bit darker than what I would normally do in post. Also, 400 seems too high, so I try to rate the camera between 200 and 400 and light for that, being careful not to clip.

Shane Hurlbut, on his blog, says he rates the camera somewhere around 250 ISO and I think that's a good method so that you can get enough light into the shadow areas so they dont get noisy, but it doesn't bring up the shadows so high where they're no longer pools of darkness. Of course you can push the shadow areas down even more in post, but sometimes that just looks like crap.

In the end, it's best to test, know what you want your scene to look like, get it close enough on set (keeping your tests in mind) and rate the camera at ISO 250-320 (and watch for clipping) in order to get rid of noise but still have your image the way you want it.

PaulDelVecchio
03-21-2013, 02:54 PM
Also, remember, this is my opinion, but I've noticed that if you bring your shadows up to maybe 15-20 IRE on an RGB parade, that gets rid of a lot of the shadow noise. So what I try to do is (if I'm lighting with lots of shadows) pretend my 0 IRE level is anywhere from 15-20 IRE, and fit everything in between that and 100IRE.

That's such a "by the numbers" way of looking at it and it's not always practical, but it's a loose rule I go by if I have access to scopes on set. This is just my personal taste. Test to see what you like.

PaulDelVecchio
03-21-2013, 03:03 PM
Not sure how the waveform would align with raw, probably just gives SDI video level values from the monitor path. But the general idea is to get as much exposure as possible without exceeding 100 IRE max white level on the waveform. Watch your zebras for raw clipping.

From what I can tell, the SDI out is giving levels as if you shot in ProRes. To my knowledge, the difference between RAW and ProRes is that ProRes is squeezing everything between 0IRE and 100IRE or fitting everything in the Rec709 area. Raw goes well beyond that and extends it out more. How much, I have no idea. Someone else with more knowledge can answer, but that being said, I'd use a combination of RGB parade to know where you're fitting in the Rec709 space, or in other words, where you are between 0IRE and 100IRE, and then use the Zebras on the camera to make sure you're not clipping. They should line up well enough to figure it out at 800ASA.

So basically your waveform isn't really lying to you, it's just squeezing everything into Rec 709 and when you bring BMCC RAW files into Resolve and select the BMD Film setting for the clip, you'll see it kinda basically does that same thing... it pushes the RAW values in between 0IRE and 100 IRE - at least in my experience.

Frank Glencairn
03-21-2013, 04:18 PM
Exposure is one thing, ratios an other.
You can easily expose "to the right" as long as your ratios are fine, even at higher levels.

That's where a false color function comes in handy. One that can be shifted up and down the IRE though.

Usually I like my medium skin tones around 40.
But with ETTR they end up at 80 - so I shift up my false color scale 40 IRE and 80 is my new 40.
Then I take care of my ratios from there.

You can also take a light meter and do the same thing by hand, if you have enough time.

razz16mm
03-21-2013, 04:21 PM
Theoretical dynamic range limits 0-100 IRE for NTSC video, and by extension REC709 HD video is 10 stops. On real life digital TV's these days though it is more like 5-7 stops as a practical limit when properly tweaked for gray scale values.
If you keep scene contrast values within the 10 stop range with optimum exposure and no clipping at either end of the scale you should be able to get reasonably clean noise free images.

zwarte_kat
03-28-2013, 12:08 PM
Thanks guys, some valuable advice here!

iamjohnsname
04-09-2013, 10:37 PM
Lots of this thread makes total sense to me, lots is over my head.

But the one question I have is just how much light is required to expose to the right?

I have been on a shoot with a lighting guy who is throwing so much light on the subjects and we're still getting super low levels on the histogram whilst connected to Ultrascope. Despite shooting at 1.4. I had awful results when using 1600ASA so I won't be doing that ever again.

I'm concerned that the 4K version of this camera (which I plan to own), which has less DR and a CCD sensor will be even less light sensitive and will require flood lights to expose correctly.

Or am I just missing something?