D7000 at ISO 12800

Started Dec 21, 2010 | Discussions thread
leverpastej Forum Member • Posts: 59
Re: D7000 at ISO 12800

SUPERHOKIE wrote:

Are you sure about this?

I thought pushing ISO was all about analog amplification of the signal before it is recorded to the card. If analog amplification is done only up to 800 or 1600, that

is a whole new school of thought I wasn't aware of. Just like military night vision goggles, I thought the camera amplifies whatever light hits the sensor when you turn up the ISO.

There is definitely no light amplification going on in the camera (like you see in military night goggles), just an electrical amplification of the signal read out from the sensel. And it is not unusual for the highest ISO settings to be accomplished by digital amplification.

After analyzing D7000 RAW files I am quite sure the analog amplification tops out somewhere around ISO 800. There are several signs of this. First there are regular patterns of gaps introduced in the raw histograms above ISO 800. Also the read noise (measured in electrons) does not improve beyond ISO 800. Finally the masked out areas of the sensor (areas that seem to be left untouched by in-camera processing) show no amplification of black level noise above ISO 800. All of this points to the conclusion that only digital gain is used above ISO 800.

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