topic Re: 5D III: ISO changes in aperture priority mode in EOS DSLR & Mirrorless Cameras

5D III: ISO changes in aperture priority mode

mflahertyphoto — Thu, 16 Jan 2014 21:19:05 GMT

Hi,

I started noticing not long after I bought the 5D III that when I'm in aperture priority mode, and set the ISO manually, that when I start shooting near 30 seconds long exposure the ISO starts automatically changing before I trip shutter. It rises and the exposure time usually goes down to 25 or even 20 seconds. I have had to switch to manual mode.

With the 5D II, no such thing happened. The shutter speed (30 seconds) would just flash to let me know I was underexposing. I don't understand how the ISO could automatically change unless you set it on auto ISO (which I never use). Please tell me this is a problem with the camera, or is resettable somehow. Would probably sell the camera if this was a standard thing that you can't change.

Thanks a bunch,

Michael

Re: 5D III: ISO changes in aperture priority mode

diverhank — Thu, 16 Jan 2014 22:33:17 GMT

@mflahertyphoto wrote:
The shutter speed (30 seconds) would just flash to let me know I was underexposing. I don't understand how the ISO could automatically change unless you set it on auto ISO (which I never use). Please tell me this is a problem with the camera, or is resettable somehow. Would probably sell the camera if this was a standard thing that you can't change.

There is a setting option for exposure protection to have the camera shifts either speed/ aperture or ISO. It is most likely that yours is set to Shift ISO. You can either turn this off or to some either speed or aperture. Edit: See page 323 of the manual.

Re: 5D III: ISO changes in aperture priority mode

mflahertyphoto — Fri, 17 Jan 2014 03:10:34 GMT

Thanks. Looked in the manual but somehow missed that.