6D Auto ISO Minimum Shutter Speed question.........

So, I recently upgraded from the 5D2 and I've been using the Auto ISO Minimum Shutter speed function generally as a walk around setting. I can set the minimum shutter speed it will use on auto ISO generally to 1/125 sec or 1/250th on AV mode and use it kind of like a default. Generally I'm walking or hiking around here on Maui taking landscapes so it's a nice little feature but when I attach my 580 EX II, it doesn't work at all. Seems to stick at ISO 400 so I end up just going back to adjusting ISO manually. Is there any way to fix this or is there a good reason it doesn't work with a flash? I set my flash to high speed sync, auto, and 1/180 sec and it makes no difference. I will admit also that I am kind of a noob with using flash

It is normal behavior for Canon bodies (at least all the ones I've owned) to default to ISO 400 when flash is available. If you want another ISO setting, you have to select it yourself. I think you'd be better off to shoot flash in Manual mode.

The only deviation is when shooting flash in P mode and bouncing the flash. The camera will then lift ISO to 1600.

Since Canon always consider exposure for ambient and flash to be two separate things, in the same image, they've also chosen to use fixed ISO values for flash. You check exposure for ambient before the flash fires, thus the camera doesn't know which ISO would be appropriate for the flash at the time when you set the ambient. Changing the ISO at the time of the preflash would mess up exposure for ambient light.

Besides, Geokras is right. Switch to M mode and fixed ISO for flash. It's easier.

apersson850 wrote in post #17365217
Besides, Geokras is right. Switch to M mode and fixed ISO for flash. It's easier.

Perhaps. But this has always been something I dislike - for fill flash the logic (!) should be to give me the ambient exposure I otherwise would have had then add in some flash. This, in fact, works just fine if you set the ISO value yourself. However, if you select auto-ISO, Canon (in their infinite wisdom) decides to override what otherwise would have been the ambient exposure by setting your ISO value to an arbitrary number then add flash in on top of it. It took me a while to work out that's what they were doing and it makes a kind of cockeyed sense (at least if you look at it sideways) but I still think it's just plain wrong.

For those who do look at it sideways (and there is an argument to be made for looking at it that way) I think there should be a setting that lets them do things as they're currently done and I'd even be OK with that being the default, if Canon thinks (as they obviously do) that it's the "correct" way of doing things. But please, please, please, could there also be a setting that allows it to be done my way? To calculate the exposure (including setting the ISO value, under auto-ISO, as if no flash were present) then add fill-flash on top. That makes sense to me, but Canon (again in their infinite wisdom) does not allow it, despite it being something easily done in firmware.

...Mike