ACR cropping by default? I'm confused...

I had not noticed this until today, although I've looked back through my image

files and this phenomenon is present in all images. When browsing an image

(screenshot attached below) in iPhoto, I noticed that slightly more image is

visible than appears in ACR and Photoshop. (screenshot attached next post).

Notice the small triangle of light on the right hand side is reduced to a speck

in ACR.<div></div>

The original was NOT edited in any way in iPhoto, but when opened in ACR it looks like this (the "crop" is only a few pixels and might be difficult to see):<div></div>

Now, I thought that maybe iPhoto was perhaps "stretching" the image for some reason known only to Apple programmers, but the pixel dimensions are slightly different in each program, 3320x2488 in iPhoto, and 3264x2448 in Photoshop. The image was not edited or cropped in either program, just converted from RAW and opened in PSE, but, as I wrote above, every image in my library displays this way. I've attached the resize dialog from PSE and inset the image info box from iPhoto below. For reference (and further confusion), the E-500 manual lists the pixel count as 3200x2400.

 

I've been working seriously in digital for about six months, so I've never encountered this before. It may all be rendered moot when my copy of Lightroom arrives next week, but, in the meantime, what is causing this and is there any way to overcome it (few pixels that it is)?<div></div>

Sorry, I was mistaken: Olympus manual says 3264x2448 for RAW.

There are a few more pixels around the edge of digital slr images. Most raw processors won't show them, but a few will. I had a similar experience with canon 20D raws (and it's probably the case with all the Canon bodies): Canon's 2 included raw processors, and Adobe Camera raw, all showed the advertised size. But Raw Shooter Essentials showed approx 15 extra pixels in both directions.