VArious camras yield pictures of various shapes, so it is almost impossible to guess whether a picture was cropped, unless it is really weird. And that may have involved a weird camera.
That said, D-SLR cameras are themost popular with pro photographers to day for editorial work, so the ratio of height to width is 3:2 or 2:3, which enlarges to 4x6 and 8x12.
In broad strokes, thre are two kinds of photographers; the frame people, and the laid-out people.
The frame people sell wedding pictures and portraits, mostly, and the pictures are framed, mostly. Perhaps in wood on a wall, perhaps on a DVD sized to fit a 16:9 television, or perhaps framed in fancy pages inside a photo album.
The smart ones compose carefully in the camera, planning to make their phtos fit the kind of frames a client wants (see the contract) or is likely to want.
And any D-SLR photographer (some exceptions, like Olympus users) knows if 8x10 is an expected size, and wil thus leave extra space at the eges to be cropped off an 8x12 image, so that it fits on an 8x10 sheet, and goes into an 8x10 frame or mat or album page.
Different cropping for 5x7 parents' ablums, and different again for 4x6 proof albums.
The laid-out phtographers fall into editorial and advertising groups, which overlap, too.
Most advertising and many editorial pictures are shot to a layout prepared by an art director. So the photographer needs to shoot to fit the layout, which may mean lots of unused space within the camera.
I used to work for a magazine that used squares in the layout. EAch page was two squares wide and three squares high.
All my photos had to fit one square by itself, or two squares side by side or two squares above each other, or four squares (2x2) or three squares high, or six squres (2 wide by three high)
One day the assignment was phtograph a four-member family to fit two squares side by side.
I've had dozens of shots run in special sections of a newspaper over the past couple of years, and for each of them I supplied an art director with a choice of pictures for each illustration, and he chose from them, and cropped as needed, to make the pictures fit around the ads, and still look good.
For decades, either taking pictures or editing pictures for magazines or magazine-like uses (annual reports, etc.) I cropped to fit the space, bearing in mind that sometimes stories had to share pages with ads, and some pages had production processes that permitted bleeds and other pages did not, an the bleeds could be top, one side or the other or both, and/or bottom.
For a lot of work, I'd shoot cariations that allowed the picture to look better on a elft page or a right page, and often left room for type.
SURVEY:
Just finished a two magazine survey.
Fortune, September 14, 2009, editorial pictures only.
64 photos that were not in the 2:3 ratio, and 14 photos that were in the 2:3 ratio.
Sharp (which is a Canadian frree "men's" magazine with fashion, cars, watches, Porsches sedan ads, etc. but no scantily dressed women.
Leaving out the carefully shot fashion (which would have worked with a layout)
There are 71 "random crop" pictures and 8 that look like they are 2:3 ratio.
A fair number of shots in both magazines looked like they'd enlarge / reduce to 8x10 format.
NOWADAYS... a lot ofthe "frame" folks are using newfangled digital systems, including creating magazine format and book format publications where they can crop the photo to match their "vision" with having to find an album page with a, for instance, 3 x 8 inch cutout.
Same applies to multi-image collage prints.
I don't do much personal portratiture (as contrasted to editorial portraiture) but I do know lots of people are not happy having to custom-frame an odd-sided print instead of just buying a ready-made mat and frame for 8x10 or 11 x 14, neighter one of which comes from a D-SLR camera.
BAK