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Old March 2nd, 2008, 02:57 PM   #1
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White Noise - normal or problem ?

Hi all,

When we focus the 251 (standard lens) on a edge-to-edge white subject such as a large, evenly lit white sheet of paper, we can see noise on the HD monitor. Setting is Ultrawide.

Is this normal ?

This was done in order to find out why we have noise on magenta and some greens and one red in the Macbeth color chart when using the mini 35 and cineprimes.

P&S Technik tell us it's because the camera is not "that high quality". That seems like a facile way to get out of a real explanation.

However, there IS noise in a full white subject.


ps -there is no noise in full black
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Old March 2nd, 2008, 04:13 PM   #2
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How are you connecting the camera to the monitor? What kind of monitor is it?

I ask because it may be possible that the noise is being introduced after the signal leaves the camera.
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Old March 2nd, 2008, 04:46 PM   #3
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even if the camera is set to L on gain which should be 0db, you can change that in the menus under Switch catagory. check you settings here first.

its also hard to say what noise you are talking about. all cameras have some noise, even at 0 db. its normal. without seeing , its hard to say if you you are seeing is normal or not.
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Old March 6th, 2008, 02:41 PM   #4
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Try Paolo's TC3 instead of Ultrawide.
Let us know,
Eugen
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Old March 6th, 2008, 05:11 PM   #5
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many thanks. we ran another set of tests which look much better, I don't know why. I will post them as soon as I am back at my office. What's interesting is that the green/magenta effect which many have complained about here is visible in some settings and not in others. It seems to be inherent to the JVC ProHD.

Monitor is JVC HD (HDSDI), but also viewed as HD QT on a Sony GDM520 (FW via Mac) and on an Epson HDready beamer (HDMI).

Will keep you posted
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Old March 7th, 2008, 04:16 AM   #6
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The Green/Magenta is related to the CA of the lens.
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Old March 10th, 2008, 06:28 AM   #7
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Is it lens-specific, then ?

Marc, what you're saying means that there's no common link (e.g. the chip) between noise in violet/magenta and green samples on the macbeth chart seen through a mini-35 with cineprimes, and the magenta/green CA in pure white seen through the standard lens ?

Does this mean in your opinion that each lens has to be matched with specific setting(s) on the 251 ?

How is this with other cameras like Red, or XDcam ?

How is this on 35mm film ?

Would testing the camea agains white but without ANY lens give aditional information ?

many questions coming from a filmmaker who wants just THIS quality of image in his films and not anything accidental.

Thanks, guys.
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Old March 10th, 2008, 11:39 AM   #8
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Quote:
Originally Posted by Claude Mangold View Post
Marc, what you're saying means that there's no common link (e.g. the chip) between noise in violet/magenta and green samples on the macbeth chart seen through a mini-35 with cineprimes, and the magenta/green CA in pure white seen through the standard lens ?

Does this mean in your opinion that each lens has to be matched with specific setting(s) on the 251 ?

How is this with other cameras like Red, or XDcam ?

How is this on 35mm film ?

Would testing the camea agains white but without ANY lens give aditional information ?

many questions coming from a filmmaker who wants just THIS quality of image in his films and not anything accidental.

Thanks, guys.


I don't know about noise levels, but the CA from the stock lens looks just like the CA from the stock lens on the XL-H1. In fact ALL lenses have CA of some kind if you investigate long enough. Some just stand out more than others and the severity varies.
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