Saturday, April 02, 2011

Sony PMW-F3 Differences Of Opinion

If it's not one Sony video camera causing controversy, it's another. Now it's the Sony PMW-F3's turn to be the subject of disagreement. Alan Roberts has issued a technical report on the picture quality of the PMW-F3, and wrote this about noise levels:
Since the slope of the gamma curve is unity when the signal level is about 50%,
it is also clear that the noise level is only about -48.5dB rather than the claimed -63dB in the specification.
- ADDENDUM 68 : Assessment and settings for Sony PMW-F3
This prompted a response from Alister Chapman at XDCAM-USER:
Now I don’t have the ability to measure noise as Alan does and I normally respect his results, but this noise figure does not make sense, nor does his comment that the camera has similar sensitivity to most 3 chip cameras. To my eyes, the F3 is more sensitive than any 3 chip camera I’ve used and it’s a lot less noisy. The implication of the test is that the F3 is noisier than the PMW-350. Well that’s not what my eyes tell me.
- Alan Roberts F3 assessment. Confusing Reading
and Philip Johnston at HD Warrior:
I am very much with Alister on this one the F3 is the cleanest, best picture at this price point you will see and I can assure you beats all the older APPROVED HD camcorders by a mile.
- Sony PMW-F3 Investigation
The report also has a very odd passage about the resolution of the sensor:
The specification claims it to be T/11 at ISO800, and since ISO800 corresponds to 0dB gain, this means that the sensitivity is very similar to that of a 3-sensor ” sensor, which in turn implies that the pixels are about 5μm square. Given that the sensor is ‘super 35mm’ size, it must be 24x13.5mm. For the pixels to be 5μm spaced, the sensor width must be about 4800 pixels, making the sensor approximately 4,800x2,700. This fits reasonably well with the estimations in section 1.2.1, and means that the sensor has approximately 12.9 Megapixels, typical of a digital stills camera.
- ADDENDUM 68 : Assessment and settings for Sony PMW-F3
While Sony has been coy about some details of the sensor in the camera, they have clearly said that the sensor has 3.4 megapixels, so it's puzzling that the report instead comes up with a different number by a reverse calculation based on the sensitivity. Others have noted some other minor errors in the report (see: F3 BBC Report)

This may all appear to be just a minor disagreement between camera buffs, except that Alan Roberts opinion about a camera is very important; he does evaluations for the BBC, and those evaluations determine whether the BBC approves a camera for production or not. And the BBC's approval follows on to whether a lot of other broadcast institutions will allow the use of the camera.

Will Alan be joining in on the discussion? That seems unlikely. He's already sick of arguments about the Panasonic AG-AF100 and posted the following in a thread in a discussion about that camera on the DVDoctor forums: the last couple of years or so, things have been changing. Now, the questions are more along the lines of 'you've got it wrong because...', and some of the posters and postings are clearly biased for/against individual cameras and/or manufacturers.

I have always been totally neutral on such things, I measure and report. My neutrality has often been questioned; I've been accused of being in the pay of both Sony and Panasonic, so I suppose my neutrality is still observable. It will always remain so.

The recent furore over the AF101 has been the last straw. I got so angry with the continued blether about it that the fuse finally blew. So, here's my statement for the future:


If you want to talk rubbish about cameras, get on with it, I won't comment either way. AF101 tests up

BBC Mirror by Daniel Bronwing: BBC R&D White Paper WHP034
ADDENDUM 68 : Assessment and settings for Sony PMW-F3 [PDF]
XDCAM-USER: Alan Roberts F3 assessment. Confusing Reading
HD Warrior: Sony PMW-F3 Investigation F3 BBC Report AF101 tests up

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