Full Auto and ISO 400...

I have never seen my XTi choose anything, but 400 ISO for any shots taken in Full Auto; even in bright daylight. If I'm reading the manual correctly, it claims that Full Auto will chose an ISO of 100, 200, or 400. Am I missing something?

PS I know... don't shoot in Full Auto... yada... yada... yada!

In full auto (green box) mode, the camera has no clue what you're taking a picture of. It has to assume that you might need a fast shutter speed to stop action or a small aperture to give good depth of field. So it will keep the ISO as high as possible.

The only reason that it will leave ISO 400 is in very bright light when the shutter speed is very high and the aperture is getting very small.

Portrait and Landscape will prefer to use ISO 100. The other Basic modes prefer to use ISO 400.

But I've been outside in bright daylight. What's it gonna take for "green" auto to drop the ISO? A tactical nuke!

You are in the same boat I was a few months ago. I know you will not like this answer but moving the the creative modes proved to be the answer to my problems with ISO400.
--
Chetan
-----------------------------------------------------------------------
Visit my photos at http://www.flickr.com/photos/chetan_kulkarni/

There are always two people in every picture: the photographer and the viewer. Ansel Adams

It would appear that your camera doesn't like shooting in full auto, and would prefer to be exercised in one of the manual modes.

--
Conglomoreum is dead! Long live Conglomoreum!
http://www.artistlies.com

Try P mode, you might like it. It's pretty much full auto, except that you have the power to set ISO speed, and a few other minor adjustments (like exposure compensation, flash compensation, RAW mode).

what focal length were you shooting?

secheese said:

But I've been outside in bright daylight. What's it gonna take for
"green" auto to drop the ISO? A tactical nuke!

Click to expand...

Almost. Figure that in "sunny 16" conditions with ISO 400, at f/11 you'd have 1/800 shutter speed. The program curve will vary depending on the lens, but it'll probably pick something around there. Neither the 1/800 shutter speed nor the f/11 aperture are alarming - in fact, both are excellent choices for handling the needs of either action shots or landscapes - and the camera would have little reason to lower the ISO.

There is little need to lower the ISO anyway. Bear in mind that in green box mode you're forced to shoot JPEG with contrast set at +1. Under those conditions, the JPEG black level is high enough that noise is not an issue at ISO 400. I have a 4x6 print made from an XT/350D JPEG shot at ISO 1600 at contrast +1; it's a low-key photo with lots of shadows and there is simply no visible noise... none at all. I suspect that at ISO 400 you could easily print at 8x10 or larger and have no visible noise.

Various.

Oh good grief...

I love P mode... and manual (which I use a lot), but I need/want to understand how the camera makes it's decisions in ALL modes. Especially, when I hand the camera to my wife, that knows diddly about cameras, and have her get reasnable results.

dylanbarnhart said:

Try P mode, you might like it. It's pretty much full auto, except
that you have the power to set ISO speed, and a few other minor
adjustments (like exposure compensation, flash compensation, RAW
mode).

Click to expand...

Indeed. It has basically all the benefits except auto ISO - and that apparently you don't like.
--
Misha

secheese said:

I have never seen my XTi choose anything, but 400 ISO for any shots
taken in Full Auto; even in bright daylight. If I'm reading the
manual correctly, it claims that Full Auto will chose an ISO of
100, 200, or 400. Am I missing something?

Click to expand...

This is good news! My 300D and 350D always picked too low of a shutter speed for me in auto mode. I think they were using a program with the old rule 1/focal for picking shutter speeds in auto mode.

If you are having trouble getting auto mode to drop below ISO 400 then the shutter speeds must be more on the line of 1/(2xfocal), which is more where I think it sould be for a 1.6x camera.

Canon must have got tired of all the Nube's complaining about soft pictures and altered the program for higher shutter speeds and smaller apertures. That makes the 400D act more like a P&S in auto mode.

Smart move canon! They must have decide ISO 400 noise was no problem and adjusted the program.

Emm... didn't you want your 400D to act more like a P&S?

--
CityLights
http://www.pbase.com/citylights/favorites
http://www.pbase.com/citylights/favorite_portraits
http://www.pbase.com/citylights/favorite_animals
.