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Low ISO Technical Issues

Steve Berlin

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If this is the wrong forum please let me know where it belongs.

I would like to know if camera makers can provide low ISO settings that they do not currently make available, such as down to, oh, say ISO 6. I'm a gaffer but I really want to know this about high end DSLRs because for fun I do still photography. I ask here because I figure there are forum participants that know sensor and camera tech inside and out, not just for Red cameras, and better than anywhere else I know to ask.

A typical lowest ISO is 100. To open up the aperture all the way on a bright sunny day for minimum DOF you have to add an external ND filter and the problem is compounded when using flash, because maximum sync shutter speed is usually not higher than 1/200 sec. I would prefer using the camera for this exposure situation, and not using a variable ND filter.

What would makers have to do with the sensors, and especially the electronics and firmware to preserve image quality while letting the user dial in low ISOs? Would this be an easy feature enhancement?

Thank you.
 
On most digital cameras see ISO as digital gain / offset to your image... so no matter what iso you set your camera to it does not do any difference to the actual capture.

If you shoot raw you are then able to alter i.e lift or lower your gain offset in your computer / in post. If not shooting raw you are then applying this lift/offset before the the image is saved as a tiff or jpg or such.

So basically when you want to shoot ISO 6 you are saying that you want to bring down the gain of your image to almost nothing, but if shot on a summer day you kind of all ready filled the photobuckets of your sensor and they can not be brought down from pure white so such iso setting is not possible.

Same goes for bringing up the iso you are actually just showing the actual capture with more brightness / lift / gain applied.

For that reason the ND's are needed.
 
Thank you. So all gain is just digital gain, no analog electronics directly interacting with the sensor? I can see I need an education for this level of discussion :)

Well, I don't know for how long the "buckets are filled" but what about shortening it to get native lower sensitivity?
 
Oh, and are you aware of any good online sources for a curious non-engineer to read about how the camera works at this level?
 
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