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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Shadow Clipping

P

Patrick O'Sullivan

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Hey there everybody,

Just a quick question. I am doing some tests shooting wide open (T1.3) at night in very low light levels. LLO OLPF.

I cannot for the life of me get the night sky to not fill up my shadow clipping bar. I can get it low but I can't get it all the way empty.
I would think that would be normal. There is nothing but black out there.

Then I see grabs like this from the Christopher Probst behind the scenes:
Heli2_zps7zcwroe7.jpg


That sky on the upper left is pretty damn dark but no shadow clipping.
I thought maybe there was some atmosphere the backlight was picking up and on lifting it just enough not to clip but then I tried that myself (on a smaller scale) and it didn't seem to do the trick.

Note: I understand how to get no shadow clipping in dark scenes using low ISOs so please don't suggest I need to lower my ISO and open up.
Im shooting master primes wide open (which should get me almost a whole stop more than Chris had with Master Anamorphics @ T1.9) and a shutter speed of 180. Even if I go to 360 I still can't seem to avoid clipping.

Again I would think that is normal because it is a night sky, nothing out there but black. But then I saw this still and it sparked my curiosity.
I asked Chris about it but he is a busy man so I thought I would widen the net for answers.

Is the shadow clipping bar working on the Weapon now? That is the only other conclusion I thought of.
 
Well there's a lot of pollution and atmosphere out here in LA :)

Where there is no light, there is no light and the Raw Noise Level Bar can/will fill up if that's the case.

In many ways that's to be expected as there's no tonality that the sensor and lens combination can "see".

In Chris' cell phone grab there we can see he's at ISO 500. Based on that histogram and knowing the Dragon sensor, he's got about 3-5 stops more "depth" in that darkness before he'd even be crushing his blacks. Hard to tell from the cell photo and without being there myself.
 
OK great. I'm not going crazy.

Only thing is I tried to back light a haze at night and I could not get the shadow bar empty unless I could actually see the haze.

It is hard to judge from the cell phone still but I can't make out any atmosphere in that corner.

Oh well. Thought there might have been some cool trick going on.

The sky in Australia is too clean
 
Probably a dumb question but my head can't get around it just yet... Why would a lower ISO not clip blacks? Wouldn't lowering the ISO one stop and opening the lens 1 stop result in the exact same exposure? I get lower ISO means cleaner image with less noise but does it also protect blacks from crushing?

Thanks and sorry if it's a dumb question :)
 
Owen Rennie said:
Probably a dumb question but my head can't get around it just yet... Why would a lower ISO not clip blacks? Wouldn't lowering the ISO one stop and opening the lens 1 stop result in the exact same exposure? I get lower ISO means cleaner image with less noise but does it also protect blacks from crushing?

Thanks and sorry if it's a dumb question :)
Click to expand...

Not on red cameras, that's not how they work. ISO is not baked in and is basically a lut for your monitor. It's the first thing you need to wrap your head around when shooting red
 
Yeh still confused.... But thinking out loud here. The ISO is just a look, so a low ISO isn't lowering exposure, it's just making the image appear darker... So it doesn't clip shadows.
So if a scene with say 800 ISO at F/8 was slightly clipping shadows, by reducing ISO a stop and opening aperture a stop there would be less shadows clipped..?

Ok I feel like I need to learn shooting Red again from scratch :)
Just starting reading Phils book so hopefully this all makes sense soon..
 
If by clipped you mean noisy then yes you have it exactly right. Think about it like this: the sensor is set in raw at 800 ISO, it never changes. You change your ISO it changes how bright or dark your image looks on the monitor only-- therefore it will make you adjust your iris accordingly but adjusting iris is what changes how much light is actually hitting the sensor, not changing ISO
 
Jake Wilganowski said:
Just. Like. Film.
Click to expand...

Exactly. I feel like so many people miss this point and it's so important. Where most companies today are making digital cinema cameras, RED is making digital film cameras, and you can see it in things like ISO and format - resolution relation with the DRAGON sensor.
 
Owen Rennie said:
Yeh still confused.... But thinking out loud here. The ISO is just a look, so a low ISO isn't lowering exposure, it's just making the image appear darker... So it doesn't clip shadows.
So if a scene with say 800 ISO at F/8 was slightly clipping shadows, by reducing ISO a stop and opening aperture a stop there would be less shadows clipped..?

Ok I feel like I need to learn shooting Red again from scratch :)
Just starting reading Phils book so hopefully this all makes sense soon..
Click to expand...

Regardless of ISO, just opening your iris a stop would give your blacks better exposure (sensor getting twice the light).
 
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