Why doesn't profile mode on my Canon digital camera work?

My understanding is that, in profile mode, my subject(s) would be in focus, while the background would be softer, kind of like in SLR camera photos.

I did some Googling a while ago and I came across a discussion where someone explained that compact digital cameras aren’t really built for this feature because of something with the lens and lengths (apertures?). Unfortunately, I can’t seem to find this page again.

Can anyone explain why portrait mode may not work on my compact digital camera? Could it ever work, considering the size of the camera, or is it really only a capability of SLR cameras?

If you want the background to be out of focus, step further back and use the zoom.

The ability to selectively focus on a subject and isolate it is a result of depth of field. Depth of field is the range of distances from the camera in which an object will appear to be in sharp focus.

The depth of field is determined by a combination of the physical size of the projected image on the imaging medium and the size of the aperture in the lens. Small images, whether by the use of wide angle lenses, small imaging mediums, or a combination of the two, give great depth of field. Small apertures also give great depth of field. Because you cannot change the lens or sensor, the portrait mode will attempt to use the largest aperture possible.

This means that point and shoot cameras, with their very small image sensors compared to digital SLRs or 35mm film, have a small projected image and a large amount of depth of field. Even if the aperture is wide open, there can still be too much depth of field to isolate the subject. If you zoom in to the camera’s maximum focal length, you may be able to decrease the depth of field enough to isolate the subject. Dimming the lights may also help, since the camera may not have a shutter speed fast enough to properly expose the image at the camera’s maximum aperture if the scene is very bright.

If you still cannot, using manual focus will allow you to focus on a point in front of the subject so that the far limit of the depth of field extends just past the subject. This is difficult to do with a point and shoot, though, and many point and shoots do not even have manual focus capability.

Cleophus summed things up quite well. The basic problem is the small CCD sensors, which are much smaller then a 35mm negative. Profile (or portrait) mode tries to optimize things by opening up the aperture as much as possible, but it’s only going to help somewhat.

For a compact, having the background very very very far away from the subject might be the only real way to achieve the effect you’re looking for. Even then, the trouble usually isn’t worth it compared to picking up an old DSLR or maybe even one of the point and shoots with the larger sensors like the Canon S3/S5.

Among the Canon point-and-shoots, I believe the G-series ( G7, the soon to arrive G9 ) and Powershot 600-series ( 620-640, soon to arrive 650 ) have the largest sensors.

However whenever it arrives, the Sigma DP-1 is claimed to be the first compact with a DSLR-sized photo sensor. Whether it will be a decent camera beyond that, is, of course, an open question at this point.

http://www.dpreview.com/news/0703/07030807sigmadp1.asp

I have the S3 and it has problems getting narrow DOF due to its small sensor size but it can be done. The G7/9 and the A63/4/5/0 are much better at it.