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-   Sony XDCAM PMW-F3 CineAlta (https://www.dvinfo.net/forum/sony-xdcam-pmw-f3-cinealta/)
-   -   sensitivity (https://www.dvinfo.net/forum/sony-xdcam-pmw-f3-cinealta/490873-sensitivity.html)

Jim Tittle January 28th, 2011 08:34 PM

sensitivity
 
Yesterday, at our local Sony F3 event, I checked the sensitivity of the camera with my Spectra incident meter. ISO 800, at 0 db gain.

Daniel Doherty January 29th, 2011 12:43 AM

I hope you're right. I've been close to pulling the trigger but haven't due to conflicting reports on the stated sensitivity. I attended the USC release and Cinematography professor said it was closer to 400. Also, the guys who made the Convergence short said it was slower than 800. Did you use 24p as your frame rate?

Nate Weaver January 29th, 2011 02:16 AM

Depends on what gamma you use it at. Standard gamma, or Cine 1, you'd probably come out somewhere around 640-800. Cinegamma 4, and you lose a stop, maybe a little more.

But in cinegamma 4, I'm underexposing a little to save highlights, so...I'm not too concerned if an 18% grey card is hitting 50IRE anyway.

In my opinion, and I've played with the camera 3 brief times now, I'd call it 800 or very close to it. And +6 and +12 gains have almost no noise to the naked eye, unless you go blowing things up.

Jim Tittle January 29th, 2011 05:55 AM

Standard gamma, 24 fps. When I asked the Sony rep how fast it was, he said that he thought he'd heard it was about ISO 1600. Which seemed a bit unbelievable.

I wasn't trying to do anything fancy--just wanted to get a good approximate idea of how fast the camera is.
A point of comparison against cameras I use right now.

From what I saw at the demo, I would agree with Nate about the gain. It's very clean.

I'm going to start carrying smaller lights and more duvetyne...

Erik Phairas January 29th, 2011 10:09 AM

Whatever it turns out to be, the fact it can do this with 60% less noise than the ex3 is wow factor enough for me. :)

F3 vs the EX3 in a candle test.
YouTube - PMW-F3 vs PMW-EX3

David Heath January 29th, 2011 11:11 AM

Quote:

Originally Posted by Jim Tittle (Post 1612567)
I wasn't trying to do anything fancy--just wanted to get a good approximate idea of how fast the camera is.
A point of comparison against cameras I use right now. .....

The trouble with quoting ISO numbers is that they are meaningless by themselves - they have to be matched up with noise figures to give a camera-camera comparison. You can make a camera ISO whatever you like by changing the gain - which will obviously change the noise level.

Unless you've got good scientific test gear, comparing two cameras at 0dB often doesn't really tell a lot. Does camera A have a higher ISO rating than B because it's inherently more sensitive - or just because the 0dB setting has a higher noise level? My own preference is to go somewhere dark (dark streetlight at night is pretty good), and put gain in until I get a reasonable exposure. Yes, it will look noisy, but because it's challenging the camera bigtime, it becomes far easier to make a camera-camera comparison. The best cameras will look pretty good - the worst will struggle to give a picture.

Use the same street for all your tests, and it's also repeatable - unless the council change the lighting.... :-)

All that said, from what I'm hearing, the F3 is very good in this respect. That's the advantage of having fewer but larger pixels, so it's exactly what you'd expect.

Daniel Doherty January 29th, 2011 02:59 PM

All of this sounds promising. I think my credit card just jumped out of my wallet.

Jim Tittle January 29th, 2011 05:42 PM

meaning more or meaning less
 
[QUOTE=David Heath;1612621]The trouble with quoting ISO numbers is that they are meaningless by themselves - they have to be matched up with noise figures to give a camera-camera comparison. You can make a camera ISO whatever you like by changing the gain - which will obviously change the noise level.

Even with film, ISO numbers are just a starting point. And, while noise varies from camera to camera, grain patterns differ between film stocks. You can adjust "ISO" by altering development.

Calling the camera "ISO 800" gives me a very good starting point. Of course, when I mess around with the gamma, or the gain, then I'll have to compensate. But, that's not much different from pushing or pulling film stock.

David C. Williams January 29th, 2011 06:25 PM

The EI1600 figure the rep mentioned is what it's supposed to be in S-Log mode, but SNR drops from 63db to 57db in S-Log. No one not in a Sony lab can test that yet of course...

David Heath January 29th, 2011 07:02 PM

Jim, I don't disagree with any of that, just trying to say that an ISO number only really tells you what aperture to set the camera to for a given light level, it shouldn't be used to compare underlying sensitivities.

The film analogy would be if you had two film stocks, A rated at ISO200, B at ISO400. But you then found that if film A was forced a stop, it was still less grainy than B. Unlikely to happen with film, quite possible with video cameras.

Jim Tittle January 29th, 2011 07:45 PM

You say "tomato"....
 
I use light meters to measure light. If camera "A" gives me a good image with half as much light as camera "B", then I say, "camera 'A' is a stop faster than camera 'B'". I know that's a gross generalization,
but it works for me.

Sounds like you're saying that there are a lot of factors to consider when comparing video cameras. I couldn't agree with you more.

Walter Brokx January 30th, 2011 11:01 AM

Noise is important in the ISO equation, because 0 dB means nothing: it's just a starting point, not a scientific startingpoint like 0 degree Celsius.
To check the noise you'll need to capture the SDI-signal so you don't have any compression surpressing noise in the comparison.

Inna Lantsman February 2nd, 2011 12:44 PM

It actually would be very interesting to make the comparison as per Erik Phairas post with PMW-F3 and Panasonic AG-AF100

Leonard Levy February 2nd, 2011 02:44 PM

Quote:

Originally Posted by David Heath (Post 1612752)
A rated at ISO200, B at ISO400. But you then found that if film A was forced a stop, it was still less grainy than B. Unlikely to happen with film, quite possible with video cameras.

My memory might be off, but if I recall correctly about 25 years ago (when I shot film) this was exactly the case with Tri-X vs 4-X at least in 16mm.

It sounds to me like the consensus is simply that its damn fast, which may make it easier to be happy with slightly slower and thus cheaper lenses. Actually it might be easier to have a camera that is not faster at 0DB but clean in the gains as you will not need to load up on ND outside or even in normal lit interiors to get a wider stop. Wouldn't really want anything faster than 800 if the gains are that clean.

Erik Phairas February 2nd, 2011 06:44 PM

Quote:

Originally Posted by Inna Lantsman (Post 1613898)
It actually would be very interesting to make the comparison as per Erik Phairas post with PMW-F3 and Panasonic AG-AF100

Hell yea, I'd love that.


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