idea: hack below 100 iso, who needs ND filters

B

backwheelbates

Member
I looked around and I couldnt find any topics on this.

I've been using ND filters to shoot video with a wide open aperture (for shallow DOF), and a relatively low shutter speed (1/50 second for 24p), as Im sure a lot of you out there are as well. But I'd love to ditch the filters and just reduce the iso sensitivity to below 100, say 50 or 25. Does anyone know if this is something that the hack is capable of?

According to wikipedia there are some really low iso films out there! This seems like something that would be easy to do in digital terms.

http://en.wikipedia.org/wiki/Film_speed

Thanks for any ideas, or feedback.

Cheers!
 
Given that in sun light one has to reduce the exposure by six steps to get it right at 100 ISO with 1/50 second shutter and f/2.8 aperture. Six steps mean you'd need to get sensitivity down to a whopping 1.5625 ISO. I doubt it would be possible to lower the electronic gain of the sensor that much. And so far there's no info at all that the firmware even has the ability to change the ISO range of the sensor.
 
It has also been noted that when you use a different iso value other than the camera natives, you beguin getting unwanted noise... besides.. a ND fader aint that expensive after all..
 
The camera will have its best dynamic range at the native ISO. When you increase ISO (gain) it introduces more noise into the dark areas and you get less dynamic range. This is the compromise for increased ISO.

When you decrease ISO from the native (if that were possible on GH1), I think you will start really clipping the highlights. The sensor already has a very sharp behavior as it get into the highlights instead of gracefully bending the curve over. So, while it may seem like an easy solution to decrease ISO, I think the results will be very poor. Dynamic range will be cut even faster than it is when boosting ISO. It is no wonder that most video cameras only have one step of negative gain (usually -6 dB) below 0 gain, if they have that setting at all.
 
Actually I think it's possible that patched ISO's below 100 could reduce the amount of visible Fixed Pattern Noise by crushing it into black. I'd personally find 1/3rd-stop ISO's down to 10 very useful.
 
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