Auto ISO

After being a digital user for many years, this week, for the first time, I tried out the Auto ISO function. I was on a trip where the lighting level was prone to keep changing and I wanted to keep the shutter speed and aperture at manageable levels. So I set it to manual (1/125 @ f5.6) and chose the Auto ISO setting, my thinking being that the ISO was less important than the other two criteria. It worked like a charm. Does anyone else use this system regularly, and what do you think are the pros and cons?

I use it all the time on a 5d3. Its the first body I had that it actually worked decently. Generally in AV and set the min shutter speed for the lens and go to town. Seems silly but I actually never thought to use it in manual. In manual I would get way more shutter speed control.

Roy Mathers wrote in post #16523847
After being a digital user for many years, this week, for the first time, I tried out the Auto ISO function. I was on a trip where the lighting level was prone to keep changing and I wanted to keep the shutter speed and aperture at manageable levels. So I set it to manual (1/125 @ f5.6) and chose the Auto ISO setting, my thinking being that the ISO was less important than the other two criteria. It worked like a charm. Does anyone else use this system regularly, and what do you think are the pros and cons?

Anytime I am in shifting light levels, I use M mode + auto ISO. In my mind, this almost makes it so I never use Av (my previous choice for shifting light).

The best way to think of it is that with digital we had two modes:
Av = Aperture and ISO priority mode.
Tv = Shutter speed and ISO priority mode.

So obviously there is a missing mode. Where is the aperture and shutter speed priority mode?

Canon has now kind-of given us this missing mode by letting us shoot M-mode + auto ISO. What is still missing though is some way to input exposure compensation and a way to make it keep working if we also use flash.

The mode currently does not work with flash. The ISO just defaults to 400, which makes it now M-mode with fixed ISO (and just what the heck is the point of that?)

It is frustrating that with almost two decades of digital SLR cameras, Canon has still not quite adapted their thinking to a control scheme that recognizes ISO as just another variable. The control scheme of the camera is still kind of based around the film system where the ISO was set when you loaded a roll and could not be changed from shot to shot.

As ISO is usually the least important variable (of aperture, shutter and ISO) it really should be the dependent variable most of the time.

^^^ All completely true.

To the OP; Careful, you may get told to learn how to use your camera properly

I once said the 5D2 auto iso was annoying as it didn't have the ability to select the minimum shutter speed, only 1/FL, and got jumped all over for being a noob / being lazy, you name it, and got told that auto ISO was not useful ever and a stupid feature that no-one would / should ever need / want


Anyways, I use auto ISO 99.99% of the time on the 5D3 and I love it. I always shoot in Av, and I'm always shooting people. I basically don't really care what my shutter speed is, so long as it's 1/125 or faster, and I don't really care what my ISO is, so long as it's as low as it can be and still give me 1/125; there's zero benefit to me to being above 1/125 unless I'm trying to overpower natural light with flash or whatever - then I'll be on manual mode and manual ISO - but in all other situations, me picking the ISO is a zero value-add function in my opinion -- the camera can do it just as well as I can, so there's really no reason i want to be doing it myself.


Canon were at least a generation behind on implementing this properly, and having got used to having it on the D700 (i went canon->nikon->olympus->canon, but that's a different story), it was a nightmare moving over to the 5D2 as I kept forgetting to set an appropriate ISO -- the habbit had completely left me.


If you shoot with large apeture primes, you may quite reasonably want to go from f1.4 to f5.6 between frames.. that's 4 stops. That's enought that you need to adjust your ISO even in constant light and it's VERY annoying to have to keep adjusting the ISO constantly as you flick between apetures when you've unlearnt doing it on auto-pilot. Was one of the two main reasons I upgraded to the 5D3 (the other being the AF system of course).

RMH nailed it. I didn't really care for auto-ISO in the 5D2...I think the minimum speed was locked to 1/60 or something like that. It's been improved on the 5D3, but I really like the way auto ISO works on the D700 (and I assume later Nikon cameras).

bacchanal wrote in post #16523994
RMH nailed it. I didn't really care for auto-ISO in the 5D2...I think the minimum speed was locked to 1/60 or something like that. It's been improved on the 5D3, but I really like the way auto ISO works on the D700 (and I assume later Nikon cameras).

I don't think the 5D2 has any user-defined shutter speed limits for Av mode with auto-ISO; I'm pretty sure my 6D was my first Canon that had that limit.

BTW, It's probably the same on most of the newer cameras: you can sort of simulate auto-ISO with flash on the 6D by using "ISO safety shift". I use it sometimes by setting the camera to Tv-priority, and ISO safety shift, and then set the ISO manually to the highest I expect it to be useful and the camera will downshift the ISO to avoid over-exposure, and you can use EC. The only problem is that the lens is usually wide open doing this in low light, and I prefer 2/3-1 stop down most of the time.

It definitely wasn't locked at 1/60. I think it was 1/FL, rounding down to the nearest ISO value or something similar. Used to drive me nuts with my 35mm prime - 1/35 might be enough to stop camera shake, but its bloody hopeless for freezing a toddler

Just did a shoot with my 6D last night. M with auto ISO worked like a charm. I knew I needed 2.8 and at least 1/250 with variable light so that pretty much gave me ISO as the only setting to play with.
The 6D allows you to set a range for min & max auto ISO too so no worries about unexpected noise.

Anyone know which bodies allow for true Auto ISO in M? I have a 50D, and in M, the ISO is Automatically set to 400.

I use it shamelessly, particularly indoors. I'd rather have ISO grain than motion blur

Blaster6 wrote in post #16524077
The 6D allows you to set a range for min & max auto ISO too so no worries about unexpected noise.

What does it do if you set the max ISO to 6400 and it needs 12800 for the shot? If it just underexposes the image by one stop, then setting a maximum isn't avoiding any noise.

KirkS518 wrote in post #16524128
Anyone know which bodies allow for true Auto ISO in M? I have a 50D, and in M, the ISO is Automatically set to 400.

1D Mark IV
7D
5D Mark III
1DX

I would also assume the 70D works the same as these, and possibly the 60D as well but you need to check it.

I don't know if any of the Rebels have this or not, or when they would have gotten it.

Thank you everyone for all your interesting and informative replies. I can't believe that I haven't tried this function before - I certainly will in future and I'll investigate its possibilities further!

I've begun using M + auto ISO for shooting hummingbirds. There are specific shutter speeds and f-stops I like, so I let the camera choose the ISO.

JeffreyG wrote in post #16523906
Anytime I am in shifting light levels, I use M mode + auto ISO. In my mind, this almost makes it so I never use Av (my previous choice for shifting light).

The best way to think of it is that with digital we had two modes:
Av = Aperture and ISO priority mode.
Tv = Shutter speed and ISO priority mode.

So obviously there is a missing mode. Where is the aperture and shutter speed priority mode?

Canon has now kind-of given us this missing mode by letting us shoot M-mode + auto ISO. What is still missing though is some way to input exposure compensation and a way to make it keep working if we also use flash.

The mode currently does not work with flash. The ISO just defaults to 400, which makes it now M-mode with fixed ISO (and just what the heck is the point of that?)

It is frustrating that with almost two decades of digital SLR cameras, Canon has still not quite adapted their thinking to a control scheme that recognizes ISO as just another variable. The control scheme of the camera is still kind of based around the film system where the ISO was set when you loaded a roll and could not be changed from shot to shot.

As ISO is usually the least important variable (of aperture, shutter and ISO) it really should be the dependent variable most of the time.

My thoughts exactly. Auto-ISO is very frustrating in M right now without EC.

But what's even more frustrating is how flash and ambient autoexposure is calculated. I think Canon can do a much better job by changing their antiquated algorithm. While many make do with the current system, I just can't fathom why - after 15 years of digital - they have not fixed it. I envision a system where the base exposure would be perfect with every single shot (using the ETTR concept), with EC and different metering modes needed only for taste.

Autoexposure and autofocus are probably the most important tools to getting a photograph technically correct, letting a photographer not have to worry about that and think more about the content of the photo. IMO, this should be the top priority for Canon - for every camera company actually - above ridiculous gimicks that are found with each new model.

Is there someone that we can complain to at Canon?