A7c Auto ISO not working as I would expect.

[Zedster]

I have a Sony A7c. Shooting in Aperture priority mode with Sony 24/105 F4 G OSS. I have ISO set to Auto ISO; range 50-204800; Min.SS 1/250s. When I take a shot on fairly low light at F16. The camera takes the photograph at 1/30s 100 ISO which is not what I want. I would have expected it to take the photograph at 1/250s and ISO 800.

What am I doing wrong/what am i not understanding?

What I want to do is set the aperture to the aperture I desire, then let the camera chose the appropriate shutter speed, but if it requires a shutter speed slower than 1/250s I want the camera to increase the ISO to a value that exposes ok for 1/250s.

 

 

 

 

[Richard A]

In this situation, I would be using Manual Mode with Auto ISO, Set your desired Aperture and Shutter Speed and let the camera set the ISO. I use this mode quite often.

[Zedster]

I didn't realise that was possible. The Sony manual appeared to imply that Auto ISO only works in P and A. I will give that a try as it would serve my needs fine. Thanks.

There is also something weird going on with setting of the max ISO. It can be set from two places: The ISO function; Using the menu. Now I would expect the two places to point to a centrally controlled ISO setting. But randomly It doesn't work that way. Using the ISO function I set max ISO to 32000. Some time later I changed it to 128,000 using the menu. When I was taking photos I noticed the shutter speed was falling below minimum, yet ISO value was only 32000. I went back in the menu and the menu was showing 128000. The I closed out of the menu and checked the Max ISO using the ISO function and it was showing 32000. The two values were clearly not associated with each other.

[Richard A]

That’s a bit strange…

[Cameratose]

I use Auto ISO a lot. Always in Manual. The problem is you're experiencing is that you're giving the camera the choice of two parameters, ISO and Shutter. The camera is making the decision as to which one is prioritized. Just shoot in M and be done with it. 

As for the ISO, it sounds like you have something programmed.