50 ISO vs. 100 ISO

[Edalongthepacific]

I attended a lecture where a very talented professional photographer stated that ISOs below 100 were not necessarily better than an ISO of 100. I didn't question this at the time but now I am confused, especially after reading some ISO comparisons between the D4, 1DX and D800. Any thoughts?

[Petrus]

Digital sensors and the image processing systems have their native ISO somewhere between 80-200 ISO where the quality is at maximum. Making the sensor slower (smaller ISO) or faster (high ISO) brings a quality penalty. This is mentioned in the manuals also. The user must deliberately enable the use of slower ISO than the optimum one (Canon), or there is no possibility of slow ISOs at all (Fuji X-Pro1 has ISO 200 as at slowest). If slower ISOs are needed for long exposures, ND filters must be used.

[ErikKaffehr]

Hi,

It is really about exposing to the right. Optimal exposure is the one that fully utilizes the capability of the sensor. If we reduce ISO further highlights will be clipped.

Much of the ISO is just information (tag) to the in camera processor or raw converter on how to interpret different voltages.

On some cameras, ISO does also affect pre amplifiers, like on all Canon cameras while on some modern cameras like Nikon D800 ISO is pretty much a tag.

Best regards
Erik

I attended a lecture where a very talented professional photographer stated that ISOs below 100 were not necessarily better than an ISO of 100. I didn't question this at the time but now I am confused, especially after reading some ISO comparisons between the D4, 1DX and D800. Any thoughts?

[Edalongthepacific]

Thanks for the responses. You are all brilliant!