Noise and Sensor Size

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im.thatoneguy

Well-known member
I have a question related to the technical aspects of sensor size.

If you shoot 16mm your grain is going to be twice as large proportionally to the frame as if you shot on 35mm with the same size stock. Will a similar effect be true of noise? If you shoot windowed 2k or windowed HD vs scaled 2k or scaled HD will the noise be twice as apparent since each pixel can't be averaged with its surrounding neighbors?
 
Well, technically it is not a blow up--it is a crop. The grain (what little there seems to be) will be the same size. It's just that it will be proportionate to the entire 2k image.

My guess is that there will be no problem, unless you project a 2k image over 4k worth of real estate.
 
lpcvideo1 said:
Well, technically it is not a blow up--it is a crop..
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er, yes exactly. In my dislexic way of thinking the grain/noise (however minimal) will be 'blown up' by 200% or so. Based on the RED footage we've seen this should not be a big problem. Much better than film it seems.
 
im.thatoneguy said:
If you shoot windowed 2k or windowed HD vs scaled 2k or scaled HD will the noise be twice as apparent since each pixel can't be averaged with its surrounding neighbors?
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This is something that interest me too.

If you use bigger pixels you can collect more light and therefore improve the signal to noise ratio. If you use more pixels within the same area the pixel size is reduced so the signal to noise ratio is worse. So theoretically noise seems to be inversely related to resolution (for a particular sensor area). Assuming that is correct it seems to me that if you shoot 4K with a 35mm lens and then scale to 2K or 1080p you should have an improved noise figure than if you shoot windowed. Is that right? it seems to make sense. After all there will be more light captured with a 35mm lens because it is a physically bigger format.

Martin
 
If you use bigger pixels you can collect more light and therefore improve the signal to noise ratio. If you use more pixels within the same area the pixel size is reduced so the signal to noise ratio is worse. So theoretically noise seems to be inversely related to resolution (for a particular sensor area). Assuming that is correct it seems to me that if you shoot 4K with a 35mm lens and then scale to 2K or 1080p you should have an improved noise figure than if you shoot windowed. Is that right? it seems to make sense. After all there will be more light captured with a 35mm lens because it is a physically bigger format.

Martin
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Yes. Greg Lowry reported on this very aspect over at DVinfo.:)
 
mike the beginner said:
Yes. Greg Lowry reported on this very aspect over at DVinfo.:)
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Thanks for that Mike.

It validates what I was suggesting before that there may well be an advantage to using an S35 2x Extender if using S16 lenses for 2K or 1080p to take advantage of the full sensor area. There shouldn't be a significant light loss cost in using the extender because that would be regained when downrezzing. But you would gain significant resolution (potentially up to 30%) by side stepping the effect of the optical filtration. This does assume that the S16 lens + 2x Extender configuration is up to the job and you could only be sure of that by running some tests.
 
We did display a 2k section of the 4k image via the 4k projector at IBC during testing. It looked superb, and I think anyone would be happy with the native pixel for pixel quality of the RED camera.

The way I like to think of it, is that when you use a pixel for pixel mode, it looks great, and when you scale down, it can look better, but that doesn't stop it looking great pixel for pixel.

Graeme
 
Graeme_Nattress said:
The way I like to think of it, is that when you use a pixel for pixel mode, it looks great, and when you scale down, it can look better, but that doesn't stop it looking great pixel for pixel.

Graeme
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Great to hear Graeme, I am certainly looking forward to experimenting when I get mine.

Martin
 
It has been suggested that another advantage of oversampling (shooting in 4k then scaling to 2k) is gaining latitude. If you really can underexpose by 1 full stop and essentially get that shadow information to show up when you scale down that would be tremendous.

Blair S. Paulsen
RedOne #19
 
Graeme_Nattress said:
I'm loving the frames I'm getting to work on. It's amazing to see yourself in 4k motion digital cinema.

Graeme
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heh heh yes Graeme you are very photogenic at 4k. Youll be able to put that one in your family album for sure.

mmmmm.. Its kinda nice realizing you can use hi rez stills from the Red as photos for the family album :)
 
Does the quality of the stills you can pull mean the unit photog is going the way of the Dodo? Just don't let the crew get so small we lose craft services, I have a major sugar jones to quell:crybaby:

Blair S. Paulsen
RedOne #19
 
I'm getting super jeaous of you Jarred.
This is ridiculous. What is a normal day for you?
Wake up... bathroom... spend some qt with the wifey.... check the million pm's I got on dvxuser.... check the red section on dvxuser.... have some breakfast.... go by the
Red studios and screw around some.... go home.... rub it in on dvxuser.... (just a little:) ) spend some qt with the wifey, eat a little something... sleep.... do it all over again. ???
That about it? It must be nice to be the king... Well, I think I'll go swing by the RED studios on my way to get some milk... Punk :)

Jason
 
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