Okay, first off, do what the instructor says, make him/her smile (if for no other reason, the expression will hurt their face!) and pass your course.
Then do what you like. Some ideas you may want to consider:
Nature does not necessarily always compose in 2/3 35mm format. Or 6x7. Or 5x4. Or square. Why should you feel impelled to constrain yourself by these artificial guidelines? Why is an image that fits this format more valid than one that doesn't?
Secondly, rather than printing your highlights darker to avoid them merging with the border, why not print a black pinline to separate the image from the border? Simply cut a bit of card (preferably black) about 2mm smaller than the image. After printing the image remove the neg from the carrier, carefully position the card on top of the photo paper and give it sufficient white light to fog a black border (about 10 seconds generally works for me, YMMV and probably will!).
Just suggestions. Once you've passed your course you're the guv'nor!
All the best,
You can try putting your mount board cropping L's around the image to see what a more defined border does for it. Also be prepared to explain to the class why using whites blending into the border works for an image. Maybe show a print with and without the defined border. Could be a good learning experience for the class.
Although I agree with most everything Frank said, I would like to add a counter point to the quoted section.
Originally Posted by FrankB
Why "constrain yourself by these artificial guidelines?"
Why live within the constraints of b/w, or print at all when you can shoot transparencies or why be constrained by film? Why use a 4x5, 6x6, 2x3 if the formate does not add some value to what it is you are trying to do.
Part of what makes this medium wonderful is that it challenges the craftsperson/artist/documenter with both its wide breadth and narrow constraints.
I am certainly not saying that you must use the full frame.
I am saying that the format is what it is, as are film and paper, every bit as artificial as any other aspect of the medium. To place no importance or even limited importance on the aspect ratio of the camera you use is a kin to shooting everything with a very wide angle and cropping to mime the desired 'focal length.'
Nature presents. The photographer composes and the frame is the canvas.