Is there an effective auto crop feature for single images in PS?

[ultrachrome]

We do a lot of film scanning on a creo scanner. The best way to do this is to slightly over scan and then crop in PS. I've tried File>automate>crop and straighten image - doesn't work properly and leaves slivers beyond the image. I've tried select "color range" and selecting the dark part around the the image (the film rebate) and then "trim" which does work really well providing the image has a very sharp straight edge but film negatives don't have this. 

I'm thinking if there was a way of doing select color range>expand selection (just a few pixels) and to end up with straight lines after "expand selection", then I would have a very effective auto crop tool for film scanning...

Any ideas?

[Stephen Marsh]

Sample images are always useful, generally more than 1 to try to take into account the variable nature of the scanning process.

[Conrad_C]

I've tried File>automate>crop and straighten image - doesn't work properly and leaves slivers beyond the image.

By @ultrachrome

Yeah, I wouldn’t go any further down that road. Crop and Straighten Images is a relatively simple feature designed to look for the empty spaces between snapshot prints you throw on a flatbed scanner, and is not well adapted to other kinds of scan trimming such as film frames. If the space around an image is not perfectly uniform and clear, like when prints are too close together, have borders, or are multiple images actually printed on paper that has a background or texture, there is a high chance Crop and Straighten Images will guess wrong, which is what you already found.