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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 :)

Question about noise.

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Francis

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I haven't been able to make good use of the search function because nothing comes up when I look for 'noise'.

Here's the question: How do I film a very dark room with low noise. Say I have a shot where the camera is on the ground in an unlit room, then a character from the outside goes and opens the doorway to light. How would I get zero noise from the black?

Even shots with lots of lights still present with noise. I've been doing shots with plenty of lights I think (several 6k HMIs), floods, those panels with multiple tubes but no matter what I do, there is noise on the camera viewfinder and viewer (viewed in REDSpace, REC709, whtv), REDCine-x, Quicktime output. I just can't escape from the noise. :cursing:
 
There are several things to think about when talking about noise.
Most important is exposure. It's not the amount of light you're using
It's about how much light hits the sensor. One rule with digital sensors is
Don't underexpose too much. Try to feed it with as much light as possible
without clipping highlights you want to keep detail in.
And watch out that you don't hit the noise floor in shadows you will want to
see detail in. I'm not sure where the noise floor begins with the new firmware.
Maybe someone else knows, or you have to test.
Than pull the brightness down in color correction.
Always remember that the native ISO of reds sensor is 320.
Another thing is to expose the rgb channels equally to use their
full bit range. Avoid underexposing the blue channel for example
when shooting under tungsten light, cause rebalancing the white balance
will gain the blue channel and bring up noise.
Also I would reccomend Neatvideo noice reduction software.
It does a perfect job without softening the Image.
After getting rid of digital noise I render a bit of grain on the
picture. In my opinion that makes it appear sharper and more
natural. Hope that helped a bit...
 
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Kim Frank said:
There are several things to think about when talking about noise.
One rule with digital sensors is Don't underexpose too much. Try to feed it with as much light as possible without clipping highlights you want to keep detail in.
Click to expand...

Thanks for the response Kim.
I'm working with a Canon Prime lense with T-1.4. From my understanding, the aperture setting for this lens is fixed. I imagine that can just put an extreme amount of light on things like people and then bring up the shadow values in post but is that what should be done? (a part of my belief is that post should be used only for enhancing light, tone and color and that the lighting should be set prior to shooting).

I guess in effect, I'm trying to understand how much light, is too much light. Right now I feel that I'm constantly underexposing (fixed aperture) with a large number of lights. My histograms show that mostly everything is pulled to the far left region with the blacks (underexposure?)
 
I don't really understand how you are shooting with 6k HMI's at a f1.4 and still getting an underexposed image inside a room. I think if you posted some stills there are a lot of people here who could help right away.
In general, too much light is when something that needs detail is clipping. Too little light is when something that needs detail is underexposed and needs to be boosted in post. Your goal, as Kim said, should be to crush shadows in post, not raise them. This will drastically reduce noise rather than add it.
By the way, I assume you have the camera ISO set to 320?
 
blacks should look just like that - black. So long as you are not trying to bring up your exposure in post, underexposure shouldn't inherently give you more noise. Try crushing the blacks a little in redalert and see if your happy.
 
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Yes I'm shooting at ISO 320. I've heard about crushing blacks to decrease noise and have tried to understand it better. Is it where I bring down shadow and dark values? (I'm working out of Cine-X).

On a histogram, are the colors clipping if their peaks are beyond the maximum y-axis value?
 
Another thing to consider is painting the room a dark color.
A white room underexposed to look dark will look WAY noisier than say a dark blue room. Less underexposure is required to make the dark blue room look "dark", therefore, less noise.
 
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That makes total sense Dylan, I didn't even think about that. I am filming in a white-walled room
 
Please post some stills!
I don't understand how you end up with noise in a white-walled room with that much light…
 
There's really no politically correct way of putting this, and I don't mean to offend, but I wonder if it would be helpful to have a "Beginners" forum in here. I think the responses previously offered are assuming that Francis has at least a marginal background in cinematography and it's entirely possible that he doesn't know that he can open up the lens. I'm guessing the aperture is set to a T/16 or similar. There's no way you can get a dark image with a lens set on 1.4 with 6Ks and ISO 320.

So at the risk of getting my head chewed off, Francis... are you aware that the lens you're using has a ring on it marked something like 1.4 - 2 - 2.8 - 4 etc. and you can twist that ring from T/16 or 22 around to 1.4 and bring more light into the lens?

I was on a shoot with a bunch of volunteers a couple of weeks ago, and when I asked one of them to zoom in to a close up, they told me there was something wrong with the camera. When they zoom in, the image goes out of focus. I thought maybe the back focus was off. I checked the shot and of course, the person had never used a manual focus camera before.

There are thousands upon thousands of reference materials both online and in books out there. If you've got no video, cinema, still etc. background, I think you need to get some experience shooting with a still camera, or cheep video camera before using a RED camera. The relative inexpensiveness of this camera allows people that would otherwise never have a chance to use something of this quality... to use a high end camera; and that's a very good thing. But I think you have a responsibility as a camera operator to understand how cameras work before picking up something like the RED One. Or at least if you're going to experiment and learn on the camera, pick up a book and apply its priciples to the RED camera.

Maybe with a "Beginners" forum, instead of throwing out complex solutions to problems that are simple, the people of the RedUser group will offer simpler solutions to begin with, then work up to the more complex.
 
There are three different factors that come together:
1. the sensitivity (ASA/ISO) of the stock/sensor
2. The opening of the Iris
3. the shutter speed
Just search wikipedia for the following
1. ETTR (expose to the right)
2. Histogram (to get a better understanding of how to read it)
3. Zone System
Than reread my post and it will make more sense to you.
Again the goal is to not boost the gain of the rgb channels.
Know where your shadows with detail are and give them enough light
that they dont hit the noise floor.
And know in what highlights you want to keep detail in.
Watch out you dont let those clip (when the histogram
gets pushed out the right side)
Cause you cannot bring back information, that wasnt recorded
But generally try to ETTR = feeding the sensor with enough light
as possibl without clipping highlights you want to keep detail in.
I dont know if youre lens has a fixed appeture (I wouldnt think so)
But to give you some kind of numbers.
A 575 HMI pointed at a talent from 3 meters away shot on 25 or 24 fps
with T1.4, 320ISO and a shutterspeed of 1/50th should give you
enough light to expose properly (using the right side of the histogram)
 
Tyler Black said:
There's really no politically correct way of putting this, and I don't mean to offend, but I wonder if it would be helpful to have a "Beginners" forum in here. I think the responses previously offered are assuming that Francis has at least a marginal background in cinematography and it's entirely possible that he doesn't know that he can open up the lens. I'm guessing the aperture is set to a T/16 or similar. There's no way you can get a dark image with a lens set on 1.4 with 6Ks and ISO 320.

So at the risk of getting my head chewed off, Francis... are you aware that the lens you're using has a ring on it marked something like 1.4 - 2 - 2.8 - 4 etc. and you can twist that ring from T/16 or 22 around to 1.4 and bring more light into the lens?

I was on a shoot with a bunch of volunteers a couple of weeks ago, and when I asked one of them to zoom in to a close up, they told me there was something wrong with the camera. When they zoom in, the image goes out of focus. I thought maybe the back focus was off. I checked the shot and of course, the person had never used a manual focus camera before.

There are thousands upon thousands of reference materials both online and in books out there. If you've got no video, cinema, still etc. background, I think you need to get some experience shooting with a still camera, or cheep video camera before using a RED camera. The relative inexpensiveness of this camera allows people that would otherwise never have a chance to use something of this quality... to use a high end camera; and that's a very good thing. But I think you have a responsibility as a camera operator to understand how cameras work before picking up something like the RED One. Or at least if you're going to experiment and learn on the camera, pick up a book and apply its priciples to the RED camera.

Maybe with a "Beginners" forum, instead of throwing out complex solutions to problems that are simple, the people of the RedUser group will offer simpler solutions to begin with, then work up to the more complex.
Click to expand...

Patience o master...
 
Have your gaffer light the set to f/1.4 at 200 ASA on his meter. Then set the lens to f/1.4; the camera to ISO 200, exposure 0, brightness 0, contrast 0, gain 0.

If you're still getting noise, then there is probably something wrong with your camera.

But, as others said, please post a still of your result, and the camera settings and RED-CINE settings you used. An idea of the meter reading you're getting off of your key light would be good, too.
 
DC restoration

DC restoration

Its a monitor and eye problem, not a camera problem.

From what I understand, you want the shot to start with a black frame then someopens a door and light fills part of the frame.

You cannot get a all back frame on a monitor that does not have DC restoration, you will see video amp and all other noise sources on a gray screen.

The RED ONE does not have AGC so its black level is fixed. If you view a compressed stream though you will see more blocking on a blank gray field than on one with a full contrast range.

The normal trick is to have something very bright in the frame all the time so that there is a balance that forces the other parts of the frame to look black.

In a 35mm print, you will see a gray field, not a black one, if there is no bright area because your eye adapts to the peak bright area, if there is no bright area you will see grain and noise in the d-max of the color print stock.

It is very bad filmmaking to have a full black frame other than for a fade out to fade in for transition, you always backlight some details in the shot to give form you just make the area of the highlights smaller to have it LOOK dark, you never MAKE it dark.
 
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