X-S10 doesn't turn off IBIS / limited ISO selection for Auto-ISO

trilean wrote:

Erik Baumgartner wrote:

If the X-S10 is like the X-T4 and X100V then the dual-gain jump is indeed at ISO 500 (the X-T3 is at 800 like the older X-Trans III cameras).
Despite the read noise improvement at ISO 500, there will still be an increase in overall noise relative to ISO 400 (with a corresponding exposure increase) when shot noise is added to the equation (1/100” and ISO 400 is better than 1/125” and ISO 500”). The vast majority of noise in an image is exposure related shot noise, not read noise (what you typically see in a photons to photos ISO graph), so given a choice of lowering the SS (more exposure), or higher ISO (increasing brightness), more exposure is always preferable when possible.

Sure, less ISO => less noise, no question about that.

Yes, but it’s not because less ISO = less noise, it’s because more exposure = less noise.

But my original question was: Why is the selection of max ISO values so limited compared to default sensitivity or regular ISO selection? It's not that there is a minimum value != 160 or a max value != 12800. It's that values are missing. E.g. there's ISO 400 and 800 but _not_ 500 or 640. That just doesn't make any sense.

Probably because 1/3 stop differences in ISO noise aren’t especially significant. Why limit yourself to such a low max ISO anyway?
If you want to ensure the least amount of noise, the thing to do is shoot with lowest possible SS (avoiding motion blur issues), and the widest possible aperture (avoiding DOF, sharpness issues). If you’ve taken steps to maximize your exposure, the ISO will be what it needs to be, there’s not much sense in limiting it (except to maximize highlight headroom in some situations - but that’s best done with exposure compensation).