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Old May 4th, 2011, 04:51 PM   #1
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Detailed test of the picture profiles individual noise ratios

I've been fiddling around with my EX1, to test how to best avoid signal noise.

Here are my findings: YouTube - Sony EX1 Image Noise Test

The test is made to expose for noise levels alone and nothing else, therefore the test chart image might look a bit odd.
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Old May 5th, 2011, 05:47 PM   #2
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New Link YouTube - Sony EX1 Image Noise Test
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Old May 6th, 2011, 02:46 AM   #3
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Re: Detailed test of the picture profiles individual noise ratios

A better test is to simply shoot the same scene, correctly exposed and then look at the noise. The problem with "exposing for noise" is that the different gammas give different noise levels throughout the gamma curve and what really counts is how this translates to noise distribution in a typical scene. Standard gamma one for example has very high gain compared to all the other gammas and this results in real world images that are visibly more noisy than with any of the other curves.
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Old May 6th, 2011, 06:38 AM   #4
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Re: Detailed test of the picture profiles individual noise ratios

I am sure I could see a black cat in the coal cellar.

I just wonder what this test proves. Maybe a night shot of a street scene would shed more light on any noise issue.
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Old May 6th, 2011, 10:45 AM   #5
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Re: Detailed test of the picture profiles individual noise ratios

I don't know what it proves. It wasn't meant to prove anything, beyond the information at what gamma settings you get the least amount of noise.

I found it interesting that STD 1 was least noisy of all in the closed iris test. While everyone says that its the one to avoid in any situation.. I think that I would use STD 1 if I had to gain above 6 db in night shots.
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Old May 6th, 2011, 03:27 PM   #6
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Re: Detailed test of the picture profiles individual noise ratios

Standard 1 will give you more noise at any given gain setting than any of the other gammas due to the higher low and mid level gain. At +6db you will have +6db more noise.
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Old May 6th, 2011, 09:22 PM   #7
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Re: Detailed test of the picture profiles individual noise ratios

I did another test with a ramping going from 7.5-60% exposure on a graycard..

While Std 1 wins on the very low end, until about 10%, it quickly picks up and becomes very noisy from about 25% exposure.
Std 4 Is very noisy below 20% but quiets down thereafter.

Compared to the other Std gammas, I must say that Std 2-3 are the best choices. They stay consistent throughout the range, and are lowest on the noise overall.

On the Cine side it is clear that Cine 1 and 2 win hands down in the lower to mid end.
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Last edited by Dominik Krol; May 6th, 2011 at 10:56 PM.
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Old May 7th, 2011, 04:20 AM   #8
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Re: Detailed test of the picture profiles individual noise ratios

That's why you need to look at the entire exposure range when doing such tests. Picking just one part of the exposure range only tells you about that one part. Best way to plot noise is with a luma wedge or step chart.

Standard 3 is the closest to Rec709 so for the most accurate 1:1 reproduction it's the one to use and I think it's the standard gamma used by most people on these boards. It's also the default gamma.
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Old May 7th, 2011, 11:22 AM   #9
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Re: Detailed test of the picture profiles individual noise ratios

I don't have a step chart, therefore I did a iris ramp up from bottom up to the top, I just didn't feel like making screen grabs for every single %

40% had the biggest range, therefore I chose to use it as an example.

Part of the reason why I decided to share my tests in the first place, was to get confirmation and a discussion about what you can do to minimize noise. Also with grading work in mind.
Often times my recordings look clean and nice, but after grading it, the noise level ramps up to unacceptable levels, making it necessary to put a noise filter in post, doubling my render time.

I realized that the EX1 is very sensitive to luma changes in post. If you try to lift your mids and shadows to much the image gets noisy. Thats true for any camera out there. So my goal was to figure out how to best avoid it in the EX1.
My first goal was to eliminate the noise floor. After that I wanted to find out which setting would give me the best result (noise wise) in the shadows and mids.

There are many aspects to take account for when trying to optimize the picture profiles.
I might find the least noisy setting in the camera, but perhaps ending up with a more noisy result after grading, because I had to gain it even more in post.
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Old May 7th, 2011, 12:10 PM   #10
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Re: Detailed test of the picture profiles individual noise ratios

It's a tough call whether to increase gain in camera or in post. Generally I find it better to get the exposure correct in camera as the noise is pre-compression. Unless your shooting with minimal compression perhaps with a NanoFlash at 100Mb/s or similar, when you apply gain in post you are not only stretching the camera noise but also all the mosquito noise from the compression process.

The worst case scenario is where you have have gone half way with the camera gain and then try to add more gain in post. In this scenario the extra camera noise will be stressing the codec, so there will be more mosquito noise than normal and then adding gain in post brings up lots more camera noise and lots more mosquito noise.

It depends on what you are shooting but a bit of positive black gamma can sometimes help as this just lifts the dark parts of the image. It will add more noise to the dark areas (as it's increasing dark area gain) but does not add noise to mid to high areas.

A further trick is to use the crispening setting in the detail controls to raise the threshold for the application of detail correction. A positive value raises the contrast threshold and prevents detail correction from being applied to noisy parts of the image, thus reducing the visibility of the noise.
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Old May 7th, 2011, 02:42 PM   #11
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Re: Detailed test of the picture profiles individual noise ratios

Nice suggestion on the crispening setting, I will take a look at it. Was wondering what it did.

So you are saying that adding in camera gain is a big no no if you are gonna grade it. Adding the missing exposure is better done in post?
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Old May 7th, 2011, 03:24 PM   #12
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Re: Detailed test of the picture profiles individual noise ratios

Not saying don't add camera gain. Shooting in low light is tough and there's no right or wrong way really. It's my personal opinion that you have to go one way or the other... gain when you shoot or gain in post. I would try to avoid half and half. For example, if it takes 18db of gain to get a workable image, I would bite the bullet and shoot with +18db. Failing that I would shoot at 0db and add 18db in post, but to be honest experience tells me that that would not look as good as if I had shot with +18db in camera. The thing I would want to avoid is +9db in camera and then +9db in post as your adding significant post gain to an already stressed (by camera noise) and thus noisy codec.

It's never as simple as above and sometimes you do end up shooting at say +12db and then adding a further 6db in post, that's the way it goes.
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Old May 8th, 2011, 08:29 AM   #13
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Re: Detailed test of the picture profiles individual noise ratios

Gents,

I am finding this topic to be of great interest as it will have a bearing on a small project I wish to shoot at the next full-moon.

I am trying to capture a phenomenon known as the "Staircase to the Moon". Essentially, it is where the moon rises and reflects on water pools and wet mud in the coastal tidal zone at very low tide. It gives the appearance of an ascending set of steps to the moon.

Initially I will be filming a few seconds of pure blackness. After that, the moon will begin to rise and will be in the form of a very large, orange tinted sphere, but the more it rises the more white or silvery it will look. The reflections will not be as bright as the Moon itself, but are really what I'm trying to capture.

So I guess I'm asking if one of you Gentleman could recommend a set of settings that might carry this off? I won't have any time to fiddle with things once the moon begins to rise, so I'd like to be "in the ball-park" from the get-go and keep noise as low as possible. Fortunately, I do live where this phenomena occurs, so I guess if I get things pretty close to right I can always go back in another four weeks and tickle up the settings for the best results.

Thanks in advance

Russ
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Old May 8th, 2011, 09:14 AM   #14
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Re: Detailed test of the picture profiles individual noise ratios

Why does it have to be right on the night of the full moon? Why can't you rehearse on the nights leading up to the full moon? Then be ready for show time on full moon night. Does a slight difference the night before really matter?

Your real challenge isn't exposing for the reflections, it is the contrast between the moon and everything else.

I would use a 1/2 grad ND (or hard edge) filter with the dividing line right at the horizon. When that moon comes up, it is as bright as daylight. You've got to dim it down if you want to see subtle reflections in the mud and water at the same time.
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Old May 8th, 2011, 09:29 AM   #15
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Re: Detailed test of the picture profiles individual noise ratios

Hi Doug,

thanks for the suggestion re: filter.

I take your point about the night in question, although I'll have to do it the other way around. The nights leading up to the full moon are affected by the Sun still casting a twilight which eliminates the staircase effect, but the nights following the full moon (at least the next two) are OK as the moon rises later each night. Also, leading up to the full moon the tide isn't low enough to expose the mud banks (it goes out further as the full moon approaches.) I hadn't thought of it that way. I can experiment on the actual full moon and get the final take on one of the following nights. It won't matter that the moon will be not quite full.

Thanks

Russ
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