sensitivity change

Discuss the PMW-F3 and any other F series camcorders here
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raarup
Posts: 3
Joined: March 30th, 2011, 10:12 am

sensitivity change

Post by raarup » March 30th, 2011, 10:24 am

I got my F3 last week. Like Alister Chapman I had some problems with moire and have tried different settings to fix it.

But one thing that really surprised me is that F3'eren goes from 800 ISO in 1920 / 50i mode to 400 ISO in 1920/25P mode. This makes no sense. There ends the same amount of light on the sensor at 50i and 25P - 180 degree shutter.
Is there anything I have missed?


Morten Raarup, On Off Line
Copenhagn, Denmark
alisterchapman
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Joined: February 1st, 2011, 7:43 pm

Re: sensitivity change

Post by alisterchapman » March 31st, 2011, 7:18 pm

When you shoot interlaced the camera combines pairs of line off the sensor to create the fields. So for the first field line pairs 1&2, 3&4, 5&6, 7&8 are used and then for the second field pairs 2&3, 4&5, 6&7 etc are used. The combining of two lines of pixels doubles the sensitivity. This is also why the spacial resolution is slightly lower at 50i than 25p.
raarup
Posts: 3
Joined: March 30th, 2011, 10:12 am

Re: sensitivity change

Post by raarup » March 31st, 2011, 11:22 pm

Is that because it's a cmos sensor? I did't remember that my f800 or f350 behaved like that.
alisterchapman
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Re: sensitivity change

Post by alisterchapman » April 24th, 2011, 6:29 pm

It's the same for most cameras, CCD and CMOS. If you didn't use combined line pairs you would have interline flicker in the interlaced pictures.
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