Auto ISO on 40D

[bill owens]

Just looked at a 40D manual trying to figure out how the Auto ISO works in Tv

and Av modes. It says, for Tv, the ISO will be set automatically within 100-800

"to obtain a standard exposure." What exactly does that mean? Can't I select a

min. speed or or a max. aperture beyond which ISO will increase automatically?

If not, what can I expect to happen?

[bobatkins]

I wouldn't bother with it. The range is limited and I can't really see the point.

 

If you go outside the range it will just (in TV mode) flash the aperture to indicate it can't get a proper exposure within the available ISO range. It will adjust the ISO between 100 and 800, but who knows exactly how it decides what to use.

 

If there was a mode where you set shutter speed and aperture and the camera then selected ISO for the right exposure, that might be useful at times.

[KenPapai]

Like Bob said, not worth it. I disable it; is worthless. You're smart enough yourself to determine ISO when you are using Tv or Av modes.

 

...the bitterest beer on the planet! ;-)

[colinsouthern]

I wouldn't be too quick to write it off entirely ...

 

I'm not sure of all of the features of the 40D firmware, but on the 1D3 you can use it to good effect in situations where you want to control aperture and shutterspeed - and yet still have a degree of automation.

 

eg: You can tell the camera not to go slower than 1/60th (so that you avoid camera shake) - keep the Aperture between F2.8 & F4 (to control DOF), but vary the ISO (high ISO when it's really dark, lower ISO if the lighting improves).

 

Even at 100-800 you're still taking 3 stops of compensation - not fantastic, but better than nothing in my opinion.

 

Cheers,

 

Colin

[Burnsie]

My question is this? Does anyone think that Canon can someday do a firmware upgrade for the 40D and provide the functionality that Bob suggests (camera selects ISO based on shutter and aperture settings manually set by the user)? This is something I would like to be able to set as one of the 3 options on the mode dial. Wasn't sure if this could be done simply in software (firmware upgrade) or if it would require some type of additional hardware (new camera model)?

[bobatkins]

It probably could be done in firmware, but I suspect that it may be a feature reserved for the 50D (or 60D...).

 

Canon really don't add features in firmware updates. They fix problems. New features normally wait for the next model.

 

In theory you could do it by switching to manual mode and using auto ISO - if auto ISO worked in manual mode. However if I remember right, in manual mode Auto ISO simply selects ISO 400 and doesn't change it.

[jason_hall4]

Sure they CAN. The question is IF they will. I would not hold my breath unless it is considered an issue that will affect sales. That does not look like the case when you look at hard it is to find the darn things in stock.

 

Jason

[steve_dunn2]

<p>An option that lets you set shutter speed and aperture (and optionally exposure compensation) and then picks the right ISO to get the shot would be nice*; sometimes you care about both shutter speed and aperture and ISO is not so important. It would certainly be something that could be added via firmware; we already have firmware that will adjust ISO according to some program that links it to light metering, aperture, and shutter speed in some other modes/settings. But I'm not holding my breath for this option to appear in a future body (maybe it will, maybe it won't), and as has been pointed out above, adding nifty new features isn't what Canon's firmware updates are typically for. It might appear somewhere down the line, but not in a 40D.</p>

 

<p>I had a quick look at Canon's information about the auto ISO feature when the 40D was first announced and concluded it was useless to me. If I recall correctly, the camera will give you 400-800 as its usual ISOs, and only use ISOs slower than 400 if there's too much light for 400 (which almost never happens). I suppose this is the safe way to do it, ensuring that you stay away from being on the borderline of not enough light as much as possible, but to me it's completely bass-ackwards. I want the lowest ISO that will get the shot. 400 and even 800 have pretty good noise performance on modern DSLRs, but it's unavoidable that 200 and 100 are better; physics dictates this. I hated grain in film; I hate noise in digital, so I want as little of it as possible. The 40D's auto ISO mode seems guaranteed to produce more of it than necessary in many situations.</p>

 

<p>Here, let me put on my curmudgeon hat and say something perhaps a bit provocative. Isn't a "creative zone" mode with auto ISO perilously close to an idiot mode? "I want to take control of this picture, so I'll go into a Creative Zone mode, and I just <em>know</em> the right setting is [insert chosen aperture or shutter speed here], but I can't be bothered picking an ISO; that's too much thinking, so I'll let the camera do it for me."</p>

 

<p>*: Um, hasn't Nikon had this for a few years now? I seem to recall spotting something like this in the manual when I was trying to teach a friend how to use her brand new D70.</p>

[KenPapai]

Like you say Steve, putting out-of-the-box auto ISO mode in the creative zone of the dial is almost like the Idiot modes. I couldn't agree more and is why I disabled it pronto. It's not being a curmudgeon at all. I was a bit checked when I first saw it -- why not limit that to the d-Rebs then? That makes a lot more sense for Canon.

[bill owens]

Thanks for the responses. Why is Canon avoiding such a useful feature? I just looked at the Mark III's manual and it doesn't seem to do much better (it has an ISO range setting but no min/max speeds/apertures).

 

Last year I shot a stage performance with rapidly shifting light using a D200 with auto ISO enabled and it was a great, if not perfect. The perfect implementation would be (1) set the ISO range (optional), (2) set a minimum and maximum speed for Av, and a minimum and maximum aperture for Tv, (3) set your default/preferred ISO, (4) shoot.

 

So, for example, if shooting action in rapidly varying light, you might decide that 1/200th is the minimum you can tolerate to stop motion; if you open the lens to the widest you can tolerate for DOF, and there's not enough light, the camera shifts the initial ISO up to compensate (but not beyond the highest level you've set in the range setting). This means you stop motion in low light but reduce noise in bright light. In this scheme, if the light gets really bright, and you've set the max speed to, say, 1/1000th because you know anything above that is wasted, the auto ISO would lower the initial ISO for ideal noise reduction.

 

Likewise if you're in Tv mode, and you want to ensure a minimum or maximum DOF in quickly changing light conditions, this feature could be useful.

 

If you're fast enough to change speed/aperture and ISO on the fly, then this "noise reduction" feature may not be useful.

 

Would this really be that hard to implement?

 

Maybe on the 50D...

[uncle_ziba]

This feature very useful for me. I can't count how many times I forgot to reset the 1600 ISO on the 350d and end up with grainy pictures in broad sunlight. (btw same issue with forgetting to reset exposure compensation).

 

At least canon is now smart enough to reset auto bracketing. I wish they also did that with ISO (AUTO ISO is as close as it gets) and with exposure compensation.

 

I think auto ISO also tries to keep shutter speed above 1/focal length which is a good safety net.

 

Sometimes there is just not enough time to go through a checklist before taking a picture. If something can be automated I want to use it.

[bill owens]

Checked out the Mark III more closely--it has all the right features for perfect Auto ISO. By setting min/max speeds, apertures and ISOs, then setting ISO safety on, it works like a charm.