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I'd like to know where I can check if my Nikon D810 introduces more or less noise from using the expanded "Lo" ISO setting: ISO 32. There's already the topic Should I use low-end expanded ISO? on this website, but this doesn't help me figuring out whether I should use the low setting if I wanted more noise.

Some reviews argue that the low ISO setting exactly doubles the light information in the produced raw file for every pixel, suggesting it is a software-related trick, but something inside me hopes it's just a trade-off of DR for a cleaner image, and I like the sound of ISO32.

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Cameras have ONE native ISO value (the sensor collects the photons that it can collect). Higher and lower ISO settings are manipulations of that. High ISO just boosts the signal up, bringing the noise up with it. LO ISO shifts it down, pushing the noise down with it. However, that then leaves the top section devoid of bright data (there is additional manipulation of that), so overall there is a contrast increase and dynamic range decrease. They do NOT call it ISO then, it does not honor formal specs. The 810 specifications say ISO 64 - 12800. It also has some settings called LO going one stop below ISO 64, which is Not called ISO 32... it is called LO.

Nikon manuals say best results are to Not use LO ISO. The 810 manual specifically alludes to that on page 110 of the User Manual.

  • Could you expand on what circumstances one could justify using the Lo setting? I mean, say I know my picture will not contain highlights, and I want a crisper image. Would this call for Lo32? And would we genuinely perceive the image as cleaner(, since your answer suggests it simply "downscales" the noise, rather than less physical noise being present)? – user55789 Dec 10 '16 at 22:29
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    Don't really know, I'm guessing. Maybe if you needed to reduce the exposure. Or wanted to slow shutter speed more. When you might otherwise use a ND filter maybe. Or if somehow the lighting was otherwise too intensely bright? – WayneF Dec 10 '16 at 22:46

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