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-   Sony NXCAM NEX-FS100 CineAlta (http://www.dvinfo.net/forum/sony-nxcam-nex-fs100-cinealta/)
-   -   Lower ISO please! (http://www.dvinfo.net/forum/sony-nxcam-nex-fs100-cinealta/521784-lower-iso-please.html)

Luc De Wandel February 21st, 2014 03:39 AM

Lower ISO please!
 
Please, please Sony, come on and give us a firmware for the FS100 that will permit to choose a lower ISO-value than 500! I'm spending a fortune on ND-filters for all my lenses. Why can DSLR's start as low as 100 ISO and not our beloved FS100?

Bill Pryor February 24th, 2014 11:31 AM

Re: Lower ISO please!
 
I never thought I'd want a camera to be less light sensitive, but you're right.

I use 77mm filters on all my lenses and have done that for a number of years. I just get 77mm stepup rings for each lens, and then 77mm threaded lens caps for each. For 9 lenses, the caps and stepup rings probably cost no more than around $20 (USD) per lens. So I only need one set of ND filters.

Luc De Wandel February 25th, 2014 01:55 AM

Re: Lower ISO please!
 
Good idea about the step up rings, but a little more hassle though. Would be still more convenient if Sony would give us lower ISO's. Never thought I'd ask for this in a video camera too, LOL.

Les Wilson February 25th, 2014 04:08 AM

Re: Lower ISO please!
 
No need to be embarrassed. We've had that feature in proper video cameras for decades. It's called Built-in ND filters.

Luc De Wandel February 26th, 2014 02:46 AM

Re: Lower ISO please!
 
Yeah, my PDW-F350 and PMW-320 had them, and so does the FS700. But I still think lower ISO-values would be a much simpler and better solution. Any filter will always deteriorate image quality, no matter how good they are.

Cliff Totten February 26th, 2014 06:10 AM

Re: Lower ISO please!
 
The problem with negative gain is that it reduces your dynamic range. The more you crank in back (-3db then -6db...etc) the worse your dynamic range gets.

John Mitchell February 27th, 2014 08:43 AM

Re: Lower ISO please!
 
Quote:

Originally Posted by Luc De Wandel (Post 1833191)
Please, please Sony, come on and give us a firmware for the FS100 that will permit to choose a lower ISO-value than 500! I'm spending a fortune on ND-filters for all my lenses. Why can DSLR's start as low as 100 ISO and not our beloved FS100?

500 is the native ISO of the chip - it doesn't go any lower. Just use your variable NDs and iris or buy a matte box and use NDs in stages (better)

David Heath February 27th, 2014 11:05 AM

Re: Lower ISO please!
 
Quote:

Originally Posted by Cliff Totten (Post 1834001)
The problem with negative gain is that it reduces your dynamic range. The more you crank in back (-3db then -6db...etc) the worse your dynamic range gets.

Yes, but probably more accurate to say that highlight handling is worse. (It will tend to give lower noise - so arguably shadows will benefit at the expense of highlights in terms of dynamic range.)

In the extreme, too much negative gain could mean the output could never get to white at all. Look at it this way. Increase the amount of light to a photosite, and you expect the output to increase - which it will, but only up to a limit. The camera may be designed (say) for output white to correspond to when a third of that value is reached. The levels higher than that are then available for processing to give highlight detail, via a "knee" etc.

But imagine the effect in you have two stops worth of negative gain. Even with the sensor exposed until it's limiting, the output will never reach peak white, the neg gain will mean it's only going to be equivalent to 25% peak in the 0dB case - well below the nominal 33% needed for nominal full white.

Luc De Wandel March 1st, 2014 02:10 AM

Re: Lower ISO please!
 
1 Attachment(s)
I've worked with large single-chip camera's all my life (well, since 2000 - before that there were none) as a professional photographer and I've always had ISO values as low as 50 or 100. Never have I experienced any problems with lack of detail in the highlights, provided the exposure was spot-on.

These are shots made with a Sony chip (very comparable to the one in the FS100). There is no degrading of the image quality in the lower ISO-shots. Cranking up sensitivity is known to have numerous negative effects, but the contrary has never been true.

I can't help wondering why this cannot be achieved when a large-size chip is incorporated in a video camera…

Closing the aperture is the last thing I want, because what's the point of having a camera with a large chip that produces beautiful shallow DOF, and then close the aperture so that this effect is completely wasted? Besides: closing the aperture to 16 or 22 on most lenses will have a very negative effect on sharpness and chromatic aberration. The same is true for ND's: every extra layer of glass, no matter how high the standards, will negatively effect picture quality.


By the way: 'Negative gain' is something like a 'cheerful depression', is it not? :-)


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