246 Auto-ISO Dumbfoundedness

[cmod]

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Hi All —

 

Recent 246 acquirer — what an incredible tool. Feels like shooting the world with a microscope, so detailed and texture abundant is the output.

 

One thing has confounded me, however — auto-iso. I've since been told to just ignore it, and that one should approach the 246 with an all-manual mindset. This is not the Auto-ISO you're looking for *waves hand*.  

 

Still — I'm curious! My understanding of how Auto-ISO should work is as follows: 

• you set a maximum allowable ISO
• you set a minimum shutter speed

ISO is then governed by the following algorithm: 

 

If $shutter_speed < $min_shutter_speed && if $iso < $max_iso

then $iso ++

 

The 246 has you set a maximum shutter speed. What advantage does this bring? And why would you want to limit your shutter speed in all but long exposures? 

 

Regardless, whatever I set the maximum to be, the shutter speed doesn't seem to ever abide by it. And the ISO seems to very rapidly creep its way up to the maximum, even if one can expose the current scene reasonably with a slower ISO.

 

Can someone please shed some light on this? It's the only part of this otherwise impeccably refined machine that has thrown me for a loop.

 

Thanks,

C

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[dante]

It's actually a minimum shutter speed you're setting, which is why the menu is confusing. Just set the max ISO to whatever you can reasonably live with. I would recommend putting the "max" shutter speed at 1/125, which will deliver the best results with most lenses 50mm and shorter.

 

As to the ISO going up quickly, it does seem to sometimes go up before it should, given the shutter speed in play; however, given the utterly unforgiving high resolution of this camera, it's better to have very slightly more grain and less shake when you are in very low light conditions.

 

Dante

[Joakim]

For me Auto ISO works best and most consistenly when I shoot in A mode, because I sometimes feel the camera selects a weird ISO  in manual mode. Other than that I like this implementation and that I can set a limit both based on shutter speed or focal length.