OK people, we have messages talking about several different concepts
here, and confusing them, and that's part of the reason there's no
agreement. Some of you are talking about transfers where the Finder is
involved, and some of you are talking about transfers that bypass the
Finder.
I own a Canon digital point-and-shoot and a Canon digital SLR.

Here is how it works if you install NO Canon softwa

A. Loading into iPhoto
iPhoto recognizes Canons with no additional software because iPhoto has
support for Canons built into it. This is in iPhoto, not in the Finder.
iPhoto negotiates the USB transfer with the camera directly, bypassing
the Finder.

B. Loading into the Finder
Canons generally do not support USB Mass Storage. (Many other camera
brands such as Nikon provide an option.) If you plug in a Canon camera
without any other software, it will not show up on the desktop as a
drive. Without USB Mass Storage support, the camera does not know how
to make itself show up as a drive, and so the Mac cannot directly
negotiate the USB transfer with the camera. (An earlier post says that
the Canon 350/Rebel XT does have a USB Mass Storage setting. I will
have to try that on mine.)

C. Loading into a card reader
Canons work great with card readers because the camera is not involved.
If you put a card from a Canon into a card reader, the Mac doesn't know
it was a Canon. All it sees is a mounted volume with the JPEG or RAW
format files on the card. OS X has built-in support for both JPEG and
Canon RAW, so you see them as files in the Finder.

D. Loading into Image Capture
With the OS X Image Capture utility you can easily preview and select
which photos to download, which is useful when you are keeping 287
photos on the card as a temporary backup and you only want the last 5
photos you shot this afternoon. (Last time I checked, iPhoto still is
dumb enough to allow only an all-or-nothing download, which annoys my
friends who use iPhoto. Let me know if this has changed.) Like iPhoto,
Image Capture bypasses the Finder. If you want Image Capture to open
instead of iPhoto when you plug in a camera or card, do it from Image
Capture preferences.

So please, before any of you puts forth an opinion about what does or
does not happen with a camera, you must state which of the above
transfer types you are talking about, because it changes the equation
significantly.

If you don't want to worry about software at all, use a card reader.
Direct camera connections consume camera battery power, tie up the
camera, and risk corrupting photos through USB transmission glitches
(according to some photographers). Card readers preserve camera battery
power, free up the camera, are not driver-dependent, and are seen by
the OS as a simple file transfer.

I don't see the lack of USB Mass Storage as much of a disadvantage for
Canon because a card reader is better than a direct transfer anyway,
and a card reader is already seen as a drive.

Cosmik Debris wrote:
I don't know what a Rebel is but the Powershot that we buy in this part of
the world certainly just plug into the USB bus. The Mac recognises them
with no other software required to load into iPhoto.