S30 ISO Auto Setting useless?

[Jerry]

Hi folks,

i just got myself a Powershot S30 and I'm still toying around with it. While doing so, I found that setting ISO-speed to AUTO doesn't seem to trouble the camera the least. It looks as if it is always using ISO 50 in this mode.

I checked that in dim light by setting a time value in Tv-Mode where only ISO 100 could still produce a matching aperture - when I changed to AUTO setting, the camera was no longer able to provide this aperture (showing 2.8 in red).

Does anyone know why this is or under which condition the camera might go for a higher ISO speed? I would be glad for help since I've to admit this 'mystery' annoys me a bit. Jerry

[Rustle]

I think the ISO is only automatic in the point-and-shoot modes. It would make sense that the manual modes lock into ISO50, on the basis that someone using those modes would switch to 100 or 200 if they want more light sensitivity.

I tested this by switching between Program and Auto (with no flash), and it seems to work that way. Program couldn't resolve the image with the 1-sec max shutter, but Auto went to 1/60th of a second. for a no-shake exposure.

I guess that's one of the other differences between Program and Auto. Good call, Jerry.

Russ

[Jerry]

Hi Russ,

thanks for the hint. I checked it out and made the same experience as you when directly comparing Auto and P mode. I still think it is strange that Canon implements an Auto-ISO-Setting in the non-point and shot modes that does not work. Where is the point in offering an option that does only work in modes where you cannot choose an alternative anyway...?

Yours, Jerry

[Rustle]

After further tests, I think I'm right, but it doesn't make sense that I am.

ISO50, 100, and 200 are multiples of each other, as they should be, so increasing ISO halves the shutter speed at each step. Auto mode, with it's 1/8th second max shutter speed, will push up to ISO150 in order to get a picture in that 1/8th, but will go with a lower ISO if possible.

I switched to ISO100 and found a shot that was just within Program mode's 1-second max shutter speed. Theoretically, switching to Auto ISO should either match the shutter speed (at ISO100) or be 2/3rds faster (at ISO150). Instead, the camera stays at ISO 50 and can't resolve the shot.

So, Auto mode uses ISO150 if absolutely necessary, but Auto ISO appears to do nothing for the manual modes. Might as well be in ISO50.

You're right to wonder why that is. If the Auto ISO mode only mattered in the Point-and-Shoot modes, why have the option in manual mode menus? There's no point to it. So, the Auto ISO should always move between 150, but doesn't.

I suppose we should all write to Canon and ask for this to be changed in the next firmware.

Russ

[scotten]

Canon says that ISO in auto ranges from 50-150. However as you note, the setting seems to get "stuck" at 50. BUT, in the Program Modes, ISO will auto-adjust all the way from 50 to 800, even though the manual does not disclose this fact. This means, for example, that in the "Fast Shutter" (Sports) mode, with flash off, you can shoot automatically in low light conditions, knowing that the highest shutter speed possible will be combined with the lowest ISO setting appropriate for that shutter speed. This is useful, for example, if shooting in a theatre where the actors are moving, but a flash would be inappropriate. One can also use the Slow Shutter Speed setting in this way. This makes the camera extremely versatile for quick shots in variable light, and does not require manual settings. As an added benefit, the ISO seems to set at "in-between" (i.e. ISO 600) settings not achievable in Manual mode. Try it, it's fun to play with. Works great for Macro shots in low light also.

Sam Cotten

[Rustle]

I'm not sure about it going all the way to 800. Have you confirmed that? ISO800 results in a pretty low-quality picture.

I can see the camera doing that in Fast Shutter mode (or whatever it's called), but I'd be annoyed if it did that in any other mode.

How did you test this?

Russ

[scotten]

I tested it by direct comparison with shots in Manual mode, and more importantly it was confirmed by Canon via e-mail from their tech assistance website.

Sam

[Jerry]

Hi guys,

thanks for the useful info.

By the way, in the meantime I found that in P and Av mode the camera does not offer any slower speed than 1 second. If you want to have more time, you have to go for Tv or M mode. I really like my camera (even though it breaks my heart that yesterday it slipped my fingers and fell to the stone ground, causing a nasty bump in the body (at least nothing is broken)(sob,sob!!)), but honestly I do not understand why Canon implemented so many unnecessary limits (ISO-Auto not working, no slower speeds than 1 second).

Anyone have an idea why you cannot go slower than 1 second without a 'manual override'? Since you have to use a tripod at 1 second anyway, why not allow the camera to work slower???

Confused, Jerry