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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 :)

Avoiding Noise in the Shadows

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Esteban Sosnitsky

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Hi all, I just asked this in the ASK DAVID MULLEN anything thread, but would like an opinion from all of you aswell as it probably isnt just about what the DP has to do but what the DIT or post processor has to do.
:help:
How does one produce low light images without generating noise?
I have made a few exercises and there must be something I am doing wrong because I always tend to see noise in the shadows. Can someone tell me how to produce images on red without noise in the dark areas?
Is it on camera?
Is it because I still have the build 15?
Does it depend on post processing?
Does it depend on the settings in redalert redcine?
Does it depend on the color gamma spaces?
I feel a little disappointed, I have tried very different settings and I always get noise in the shadows. Any suggestions on what to experiment would be very much appreciated. Thanks!
Thanks.
 
In build 15 blue channel noise in low light was, for me and others, quite well.... noisy (this is a matter of preference, of course). Especially in low light tungsten conditions. What was worse was that the noise had a compression artifact, which made it almost untreatable.

That has all changed with 16 :biggrin:
 
Thanks for your response!
I downloaded some footage processed by someone in the forum and they were almost noise free images in low light situations. Looking forward to see if anyone who has done that knows and wants to share.
Thanks again Fredrik.
 
One thing to note is the RED doesn't roll off the noise floor like almost every other camera. This is good because the camera manipulates the raw data less, and you get to see EVERYTHING the camera captures. BUT It takes a while to get used to having to roll off the bottom of the curve before it's usable.

Also processing with the highest quality debayer will help, as will moving to Build 16.
 
Thanks again for your replies. But I really dont understand what rolling off the bottom of the curve means. Also, I did some tests and I see a lot of noise in grey and blue areas of the image. Is this normal? Is this what they said is solved in B16?
 
It's pretty simple -- underexposed information falls further and further into a zone of noise at the bottom near black. You want less noise, then expose so that the information you don't want to be noisy is higher than the noise level.

The only risk of doing that is the other end of the scale, the clip point -- you slide your exposure information further up the scale... and push more overexposure information off the cliff edge of clipping.

So you want less noise, expose more and control the bright highlights that you don't want to clip through lighting, using darker colors in wardrobe, walls, etc. Then the shadow information will be less noisy and you can crush the very bottom of the scale into black and get a very clean image.

That or use noise reduction processing at the risk of some softening, perhaps smearing of motion.
 
estebanred said:
How does one produce low light images without generating noise?
Click to expand...

The truth as I see it is you really can't underexpose RED much if at all in low light. Which is to say, if your light meter reads ISO 320 F1.4 and you shoot at F2.8 you're going to get some ugly RED. But if you shoot at 1.4 it'll look pretty good. So sunrise, sunset where you have a pretty even 1.4 at 320 you get some nice low noise stuff even though it seems like low light. It is, but the exposure is correct. Being daylight instead of tungsten seem to help too.

I still think the camera is a 160 camera but underexposes to 320 perfectly. Go to 800 in very low tungsten light and you're asking for trouble. That has never worked great for me. It's just noisy. At least the noise pattern in 16 is more organic so you can just go with it. Scaling all the way down to SD helps make it look better.
 
I get the feeling you need more basic information? Correct me if i'm wrong.
You are probably exposing by eye. You are looking at the image in low light and you are increasing either exposure or ISO to get the image brighter and then you get the noise? If this is the case then you need to drop the exposure or iso down. If you find this creates too many shadows then you need to bring in more light. Unfortunately, really, that is the nature of image production. It is true for film as much as it is for digital.
 
If someone said "I'm getting too much grain in the 500T emulsion I'm using" -- my response would be: (1) overexpose the stock more, or (2) use a slower-speed stock, or (3) use a bigger negative format.

There's no free lunch -- too little exposure produces grain on film or noise in digital. If you are getting too much noise in the shadows, you need more exposure in the shadows. More exposure gives you the flexibility of darkening the image in post without getting more noise, whereas too little exposure not only puts more shadow detail in the noise floor, but any color-correcting in post that plays around with the shadows, particularly any attempt to lighten them, only brings up the noise.

The only reason that 3200K is noisier than 5600K is that when your lighting is warmer in color, you are basically underexposing the blue channel more and more, which is why it gets noisier when you attempt to correct that low color temperature light to "white" by pushing the underexposed blue channel.
 
Ok, thanks for your input, its really appreciated.
David, I do understand what you are saying, the thing is I have tested the camera with daylight and tungsten in different situations and I feel the camera noise is too high. Probably with B16 this issue will be different BUT I saw Gunleik's TESTS footage and I dont see that kind of noise there. I wander if he did some post effects or something, looking forward to his response.
I exposed by eye with a monitor (which is not good because of color space and due the fact that the output is 720p) but I always check with my meter to be sure and make a decision from there. I have worked with the F900 and the F23 and I dont see this kind of effects there.
I feel your input is very valuable in the means that exposing the shadows a little more will get you more info to pull back afterwords. Thanks. But for example, the other day I shot a demo which had a blue background. I lit it with daylight HMI;s and KINO flos, and the amount of noise in the whole picture was a little too high. I have an upcoming shoot which should be very contrasty. I guess I will light it flat and contrast in post? What concerns me about this means of procedure is the clipping highlights, so I will try to be more accurate on the exposure and comment on this thread afterwords.;)

Thank you all for your help. I still would like to hear if someone is doing something different in post, other than what we have discussed here. Thanks again.
 
joelnet said:
I still think the camera is a 160 camera but underexposes to 320 perfectly. Go to 800 in very low tungsten light and you're asking for trouble. That has never worked great for me.
Click to expand...

Hi Joe, I agree, I have never used the camera higher than iso 500. I tend to use 320 and either dim the lights or go to 160. The thing is sometimes, in low budget productions your lights can only be tungsten cost wise. So I am trying to experiment in both situations and see where can I get this camera to work nicely under these circumstances. I just shot a greenscreen with tungsten, rated the camera at 4000K (WB) and iso 320. I will post the results, I can say they look great. But I want you to see it.;)
Nevertheless, whenever the light falls under zone IV I feel the noise is not good in either daylight or tungsten, of course I see it more in tungsten because of what david explained earlier, but I have to be fair and I havent seen that kind of noise in the Cinealtas. (Dont judge me, I bought a RED;))
 
supernovafilms said:
I get the feeling you need more basic information? Correct me if i'm wrong.
You are probably exposing by eye. You are looking at the image in low light and you are increasing either exposure or ISO to get the image brighter and then you get the noise? If this is the case then you need to drop the exposure or iso down. If you find this creates too many shadows then you need to bring in more light. Unfortunately, really, that is the nature of image production. It is true for film as much as it is for digital.
Click to expand...

Supernova, I expose with the meter and by looking at the monitor and the scene itself. I never increase the ISO, all my shoots are 160, 320 or 500 tops in worst case scenarios. Thanks for your input.:wink:
 
What kind of meter you using?

Expose for the highlights/gamma.
Do tests on your hmi's...
What monitor are you using?
Try tests using full stop range and bring into studio and find where noise stops. Find the discrepancy with your light meter readings and adjust accordingly.

If you are using just the small lcd and light meter, then i would say this is a light metering problem.

I mean if you see the noise on monitor why don't you just drop exposure???

Or does noise still occur when you do this?

If so then yes please post frame grabs...
 
Just finished another shoot. I applied what you have suggested and I have to say I feel the problem has been minimized. I over exposed a stop of what I would have decided previously and then pull down the curve in red alert maximizing contrast, deep blacks, rich mid tones and highlight detail are present. I feel the problem was that nailing the exposure is really hard when the monitor looks like when you set the color space and gamma in red alert in REC709 which is very saturated and bright, then your meter says something different and you chose to underexpose. Then upload into red alert and you have some areas that are generally flat and slightly underexposed that bring unwanted noise. So I tried to level up the whole ambient light, and expose a little over the areas I wanted to bring up and then bring the others down in post. I think it works. I just came from the shoot so after a good night sleep I will play with the footage and share.
PS> We have a LMD 9 inch monitor (9050 sony hdtv),a panasonic 26inch bt-lh2600, a sekonic cine L-608 zoom. I dont think its an equipment/tool problem. I think its an issue with my inexperience with this camera, plus the lack of manuals with the software, etc. And yes, my meter has batteries thank god.
 
I shot in ASA500,T1.3,tungsten light,B16 4K 2:1 ,redcode36

and got very noise in the shadows,This is my blue channal:

So I need more exposure in the shadows?But in other words,RED can`t shot in high iso(over ASA500) especially under 3200K?
 
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