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Sony NXCAM NEX-FS700 CineAlta
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Old July 12th, 2012, 03:43 PM   #1
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Weird colour shifting and noise question

Hi,

Iīm testing out my new FS700, picture profiles, noise, the usual stuff and I found something very strange.
I uploaded a video to show it. In this video I go through the ISOs from 400 to 2000. I used the kit lens set to auto iris to have the same exposure over the whole ISO range.

http://www.steinhardtverlag.de/Felix/00005.MTS

At 25 seconds I switch from 800-1000: You can see the picture kind of flickering between magenta and green, very subtle. I had dialed in manual WB 5000 Kelvin, so the camera should do nothing to the hue like in auto WB.

Then at 35 seconds I switch from 1250 to 1600 and look what happens to the picture. The hue completely changes to magenta! What is going on here? Alister, do you have an idea?

Second question: Noise. I come from the FS100 and it was clear the 700 could not be as good, but...Itīs noisier than what I know from the RED One MX which has no internal noise reduction at all.
Good thing, itīs only luma noise nothing chroma. It seems like there was no processing power left in the CPU of the camera to do luma noise reduction.

I made this test shot at ISO 500 / external recorder and I would not use that without a little denoising. You can download it as 35 mbit x264 file. Looks 99% like the original

Or is something wrong with the camera?
Edit: TThis was shot in CG1 and cinema color.

Felix
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Old July 12th, 2012, 06:05 PM   #2
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Re: Weird colour shifting and noise question

I do see that, perhaps it has something to do with the kit lens? Maybe there is some software compensation for some property of the kit lens that isnt working right? It does seem odd that that color shift only occurs at one step, but the fact that it flickers may indicate it is connected with the iris since the iris may have been flickering as it may have been right in between two autoiris steps. The steps of the iris may not match up exactly with the ISO steps, and it is possible there is some software bug dealing with some communication with the lens that causes the shift? All really just theories but maybe you should try the test again and try it with a different lens and see if you can reproduce the issue.
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Old July 13th, 2012, 02:11 AM   #3
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Re: Weird colour shifting and noise question

Did you have auto shutter speed? If your shutter speed is changing this can introduce colour phase shifts and flicker if you have any type of fluorescent or discharge light.
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Old July 13th, 2012, 06:20 AM   #4
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Re: Weird colour shifting and noise question

Nope. Shutter was set to 1/50. 2 Arri 650, one offscreen.

I remember my old GH2 doing almost the same when switched from 640 to 800.
Itīs no problem, I can make a second PP with corrected WB shift, but Iīm not sure if the camera is ok, also because of the noise amount.
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Old July 13th, 2012, 09:23 PM   #5
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Re: Weird colour shifting and noise question

Canīt someone with an FS700 test this, please? Just switch from ISO 1250 to 1600. Any hue shift? In manual WB with dialed in Color Temp.

Last edited by Felix Steinhardt; July 14th, 2012 at 12:49 PM.
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Old July 14th, 2012, 01:35 AM   #6
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Re: Weird colour shifting and noise question

I can try to test tomorrow after my FS700 arrives!
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Old July 16th, 2012, 01:02 PM   #7
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Re: Weird colour shifting and noise question

I have the same issue with my FS100. Got it installed on the roof of the house as a kind of webcam to follow kestrels. Got auto shutter plus auto gain limited to 12dB. During 'normal' daylight the colors are fine. When sun sets and it becomes dusky the colors get a nasty purple hue, obviously when gain goes gradually up from 0 to 12dB. Don't know what the shifting point is. Can't check it, since the things is on top of the house.
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Old July 17th, 2012, 12:53 PM   #8
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Re: Weird colour shifting and noise question

Set my colour temp to 5600k and went from 0db to +30db. No obvious colour shift.
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Old July 21st, 2012, 02:40 PM   #9
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Re: Weird colour shifting and noise question

Noticed it has nothing to do with the gain. it is just that at very low light the white balance seems to shift. I have fixed white balance at 5600K, but that gives a purple hue at very low light. Never noticed this with my EX3, but then again I never use it at such low light because it is not sensitive enough.
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