2k HD grainy even in full daylight?

[Shawn Nelson]

I have not filed a ticket because I don't know if this is a problem or not and would love some feedback.

I recently upgraded to release 3.3.15 and did a fresh black shade. I then went out and shot some 2k HD 239fps stuff in broad daylight, great exposure. So I had a surprise to come back to the process and see how grainy it is. Is this normal?

Here is my trimmed R3D, it's only 200mb, if anyone can open this up and look at the grain levels and tell me if that's to be expected at 2k HD in such good lighting conditions

http://www.descensus.com/files/A001_C039_0113NM.RDC.zip

Thanks!!

 

[Gunleik Groven]

Downloading, but 2khd should be (at least) 4x as grainy as 4khd, probably a bit more due to signal/processing issues, when displayed at 1080.
Loves a bit of contrast and that main subject is not underexposed.

Also, did you blackshade for highspeed at working temperature?

Cheers!

G

 

[Shawn Nelson]

Downloading, but 2khd should be (at least) 4x as grainy as 4khd, probably a bit more due to signal/processing issues, when displayed at 1080.
Loves a bit of contrast and that main subject is not underexposed.

Also, did you blackshade for highspeed at working temperature?

Cheers!

G

Thanks!
I definitely did not blackshade at 2k 239fps at working temp, because blackshade takes so long and I'm on location I dont have time to wait the 40 min (or whatever it is). But I did do a black shade after the fresh build install.

 

[Domenic Barbero]

yea a black shade for those speeds would definitely help a lot.

 

[Gunleik Groven]

It is kinda recomended to do a blackshade for the relevant offspeed when you go far off from "standard" framerates. You can save that blackshade and switch between them. I also see users saving several blackshades and trying to load them (loke one for long and one for short exposures).

Anyhow... even though I mostly display noisy images here... I will look a bit into them. But it might not be till tomorrow...

(kids and beds and stuff around this time over here...)

Cheers!

G

 

[Domenic Barbero]

i played with the footage. moved the iso back to 320 and added a touch of correction and that definitely helped. hit it with a denoiser as well and should cure most of it.

 

[Jeff Kilgroe]

Presuming you black-shaded at the proper resolution and frame rate, and had the sensor up to temp first, then it could be a few things. I'll download in a bit when I'm not on an iPad...

More than likely, you're under-exposed. Sensor response in terms of ISO or mid-grey point seems to change at higher frame rates in my experience. The noise floor comes up as the sensor cycles faster, that's really the simplest way to say what happens and what is most likely going on here. You have to lower your mid exposure point or treat the camera as if it were a lower ISO camera. Unfortunately, while this will bring up exposure in your shadows and push noise down, it crushes DR and sacrifices your highlights. Shooting overcranked requires much more attention to lighting, not simply dumping on more light to compensate for exposure time.

This effect seems to plague most CMOS cameras, not just RED. And it's a cycle issue, not a "shutter speed" issue. Shooting 24fps at 1/480s shutter is one thing. But cycling the sensor 10X faster at 240fps and still using a 1/480s shutter, that noise floor really creeps up.

There also seems to be some extra anomalies in the R3D compression when shooting higher frame rates over 120fps. Nothing I can pinpoint but stuff just doesn't always look as sharp or good. They improved 2K quality in the past with one of the builds -- build 3 I think. IMO, it could use a bit more improvement still. But it's hard to quantify, most of us only shoot 2K in situations where we need the high frame rates and there's other issues that come along with those rates.

 

[Shawn Nelson]

Thanks Jeff, I'm curious your thoughts after you look at the clip. I think it's a good exposure at the recommended iso800 (we are told repeatedly to use iso800 as native). Though perhaps iso320 should be used instead for high fps?

The time it takes to black shade is sooooo friggin long that it's simply unreasonable to do in the field unless you're on lunch break, and sometimes you don't know you'll be doing 200fps or greater until the shot occurs to you.

 

[Clark Dunbar]

I've found that 2K at high speeds is just noisy!

 

[Terry VerHaar]

FWIW - black shading on the new beta builds (4.0.3/4.0.6) seems to be much quicker.

 

[Alexey Milokost]

I have discovered for myself that the black shade doesn't really help to decrease the noise. So my recipe for clean image with high speed is:
Outdoors: rate camera at 160ISO, use really sharp glass like UP, crash blacks in post, apply sharpening and de-noise tools if needed.
Indoors: use only 3200K lights 5k and above (2Ks and lower will flicker), put 1/4 or better 1/2 CTB on each light, rate at 160ISO, use really sharp glass like UP, crash blacks in post, apply sharpening and de-noise tools if needed.
Green screen: same as indoors, +1 stop for green screen (if face is f4.0, the green is f5.6), do not use the blue screen.
Try to shoot +2 stops from the widest open. On UP f4.0 would look great.
If 300fps is the desired rate, I would rather shoot at 299fps but set a better compression - 6:1.
Any splashes of water and fast flying objects look good with 45 degree angle in Relative mode which is like 1/1200 sec
Summary: Tungsten 10k, 20k and 24k are the only ones to use.

 

[Jeff Kilgroe]

OK, just looked at the clip. It's not as bad as I feared. I think a decent de-noise pass with NeatVideo or in Resolve will clean it up just fine.

That said, the noise seems to be predominantly in the lower mid-tones and not in the dark blacks. I see more noise on the trees and shotgun compared to the black jacket. That leads me to believe it's more an exposure and possibly compression issue than a black-shade issue. Black shading is quicker on the new v4 beta builds. We also have the ability these days to save black shade profiles and load them as needed if we don't have time to do the actual shading.

For high frame rates like this, I rate the camera lower than ISO 800. ...320, even 250, if conditions are right. Of course, it's metadata, but you still need a lot more light to rate the camera that low. On your clip, if I pull it down to 320 the noise is almost gone, but it is of course dark. Pulling any part of the image up reintroduces the noise.

Like Clark says, 2K at high speeds is noisy. This comes back to the noise floor coming up as the sensor cycles faster. You have to rate lower and light more to keep it clean. A good de-noise software is also very helpful.

 

[Nick Morrison]

If you are shooting at 2K, shooting at 320 can help a lot to control noise. Also shoot at 5:1 or 6:1. If you skimp on the compression, you are more likely to see noise should the sensor get strained.