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Pro and consumer versions including PXW-Z150, PXW-Z100, PXW-X70 / FDR-AX100

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Old November 4th, 2016, 08:09 AM   #46
Join Date: Aug 2010
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Re: PXW-Z150 low light issues - help?

Originally Posted by Paul Anderegg View Post
One last note about those figures. Due to the loss of light sensitivity with increased pixel count, several manufactures have begun blatantly making up figures, FALSE FIGURES. These would be Panasonic and JVC. Both of these companies have introduced standard and "extended" modes to their line of cameras. The extended or "low light" modes add 6db of gain to the readout, so when the camera says 0db, it is actually at 6db. Because the figures are taken at 0db, they get a rating of f11@2000, when in fact their cameras are a full stop less sensitive. Remember, every 6db is a stop. The HPX370 and HM890 cameras are rated at f11@2000, but at 0db on extended mode where they receive this rating, they are noisy, and the image is identical to their standard setting at 6db of gain. Sony uses REAL image sensitivity, no games. When you see Sony say f12@20000, that is a real number, with no fake or hidden gain tricks applied.

I have owned and operated HPX and JVC camera with these modes, so this is from real world experience, not just guessed about.

But this is what happens in all cameras. When the voltage readings are measured at each pixel, (they are extremely low voltage readings) the circuit just does't take whatever it gets and calls that baseline "0db". Instead, that is all "amplified", deBayered and processed. The final result of all of that is what the camera companies will call "0db" for that model.

So, yes, all cameras have plenty of "pre-amp" work going on long before it ever reaches what the camera guy sees as "0db" in his settings. And of course, it gets even more complicated when you consider the pre-amplification needed to do a LOG curve read-out and mapping from those photosites on the sensor. LOG mapping requires additional gain processing before you ever see it on your screen/switch settings as "0db".

So, I think it's fair to say that "0db" can never be taken literally on any camera of any kind from any company. It really doesn't mean allot, it's sort of a false indicator for what is really happening behind the scenes.

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Old November 10th, 2016, 09:08 PM   #47
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Re: PXW-Z150 low light issues - help?

Cliff, what I meant specifically for the JVC and Panasonic cameras, is that they have TWO DIFFERENT 0db modes, the ones they cal extended and high sensitivity add 6db underneath that 0db you see in the viewfinder. The s/n, such as 58db they claim in specs, is for their standard modes, so you have to deduct 3db from those s/n ratios for how clean a 0db image you will get at their claimed f11@2000. It's tricks like that that piss me off. Sony doesn't do this, if they say f12@2000 with a 62db s/n ratio, that is what you get, so you can add 18db of gain and know how clean your image will still be.

My work JVC HM890 stores separate gain settings for each mode. I have standard set to 0/9/18 and extended to 0/6/12. When I toggle between modes at high setting, the image stays exactly the same, meaning 18db at standard is as bright and noisy as 12db on extended. Might as well just add 18db of extended gain and put 0db on it, call the camera f32@2000 :-)

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Old November 11th, 2016, 07:17 AM   #48
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Re: PXW-Z150 low light issues - help?

My NX5U starts at -6db but becomes very noisy almost unusable at 12db. I too always assumed that this was really 18db and the noise then would make sense !!! If you are outdoors in manual the "set ND " often appears but of course in auto the camera will go to -3 or -6 before giving this message. A case where manual may not give as good an image if one doesn't realize that 0 is not really 0.

Ron Evans
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Old November 11th, 2016, 08:46 PM   #49
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Re: PXW-Z150 low light issues - help?

See page 9 starting with section 2.4 in the below PDF. Testing of the JVC HM650 and it's pretend f11@2000 extended mode. Tester shows that standard mode is only f7.5@2000, which is less sensitive than a 1993 Sony Betacam. JVC states in their brochure that standard sensitivity of the HM650 is F11@2000, which is a flat out lie. For reference, the PXW-X180 is f9@2000 with a real 60db s/n ratio, and I found it to be as bad as the X70 in low light.


JVC still will not provide signal to noise ratios for their cameras, and their brochures state just "excellent!" or some other nonsense.

Sorry to rant, but these stupid things make it hard for us to make educated camera purchase decisions. Short of buying every damn camera on the market to test, which I seem to actually do, there is no way to know what you will get in low light. About as annoying as drivers who do not signal with their blinker before cutting into your lane...grrr.


PS: Grrrrrrrrr!
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Old November 22nd, 2016, 10:27 AM   #50
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Re: PXW-Z150 low light issues - help?

I'm glad I saw this thread. I also film theatrical performances and was considering this camera (z150) not for the 4k but bigger sensor for low light and maybe more dynamic range but now I see I avoided a costly mistake.

To add my 2 cents judging from your pictures. It seems most of the noise/grain issue are due the 1 sensor not being able to render saturated color more specifically red which always has been difficult to reproduce. At the end of the day real world performance trumps all. It's tricky making purchasing decisions on specs and assuming imagine quality improves with each generation, larger sensor, more pixels etc

I think under less colorful performances it would perform fine. It be tricky for me to quantify how many performances would cause what you experienced. Though the benefits don't seem to warrant the risks for this application.
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