topic EOS R5 C Can i enforce auto iso for a mode like Av, after switch from a Custom mode? in Professional Video

EOS R5 C Can i enforce auto iso for a mode like Av, after switch from a Custom mode?

vincent3 — Sat, 16 May 2026 13:00:00 GMT

Not your typical Auto ISO question...

Canon R5C... I usually use A priority, with auto-iso. Shooting in school auditorium with varying lighting throughout.

I have C1 programed for Manual mode, mechanical shutter, manual iso (usually low), for intermittent flash photography at events.

When I turn off flash and switch from C1 back to Aperture, the iso does not revert to Auto. I don't notice for awhile, and I take a bunch of photos in dark areas and shutter speed drops low, blurring photos. Taking a lot of photos quickly, I don't notice in Review, or the settings shown in viewfinder, till too late.

Is there a setting to to tie a specific ISO setting, in my case Auto, to Aperture mode, so it gets recalled? I don't need a button defined to make iso selection easier, etc.

Re: Can i enforce auto iso for a mode like Av, after switch from a Custom mode?

Waddizzle — Fri, 15 May 2026 22:55:33 GMT

I would suggest powering down the camera after powering down the flash. Once done, remove the flash from the hot shoe, and then power up the camera.

Re: Can i enforce auto iso for a mode like Av, after switch from a Custom mode?

wq9nsc — Sat, 16 May 2026 00:25:51 GMT

I have never used a R5C so it may be different with these bodies but with my 1DX III bodies I toggle frequently between C1 and my standard mode. I shoot high school sports which means fast shutter speed with the aperture wide open but for post score celebrations and similar I need greater depth of field so I have C1 programmed for 1/250, f 5.6, and I will either use auto ISO for it or an ISO I choose based upon the field illumination.

So I shoot in manual with auto ISO, 1/1,000, and f2.8 and use one of the assignable MFN buttons to toggle between C1 and manual mode. Using this method, all of the manual mode parameters remain the same when I toggle back including going from fixed to auto ISO.

Rodger