9x12 is an odd size, but it is industry standard.   Most professionals who do portfolio work, shoot for the crop since that aspect ratio works for a lot of things.

You can certainly use 8x12, it is fairly close.  It will fit into the pages, but it isn't 9x12.

You'll just look like you don't know how the game is played.

Not your best first impression.  ;-)

photographers should be 11x14.
models 9x12.

not sure where they ever came up with the 9x12. meh.

The 9x12 size is because it allows for tearsheets to fit nicely on the page. These days, the magazines are often smaller, so it doesn't matter so much, but the standard has stuck.

I've used everything from 8x10s to 20x30s for presentations, but 11x14s seem to be the usual thing for photographers. Some photographers use two 11x14s to create horizontals as two-page spreads.

If you shot in the 3:2 aspect ratio size your images at 12" high and 8" wide for verticals and then make the canvas 9" wide. I usually suggest black "gutters" as they will blend in with the black backing of the majority of portfolio books pages. In cases where you have a predominately light image use white gutters so that they are less distracting.

The problem with 8x12 is the empty space and slipping out of position in the book.

If you shot in horizontal you can order a "double truck" (double page spread). The 3:2 aspect ratio prints to 12" H x 18" w, divide that by 2 and you have two 9x12" vertical prints making up a single two page spread. Don't do this if it will cut faces in half. Instead make your image 6" high x 9" wide and add gutters to the top and bottom.

Now, that being said, full bleed (cropped to borderless) usually have more impact. I print hundreds if not thousands of these a week and always try to crop to full bleed if possible. From a visual perspective they are more pleasing than guttered.

Here is a three year old thread:

http://www.modelmayhem.com/po.php?thread_id=376948

Either are acceptable. Agents/clients don't give you demerits for not having the exact print size...just don't stray farther than either of those sizes.

I never have my 8x11's that I MUST use cropped... I usually have them add a border.

But I definitely prefer the true 9x12's.

I have NO use for 8x12" or 8x10" photos.  If I get them from photographers, they go into a white envelope containing other prints that size and that goes into a drawer.  If it's a shot I feel is book worthy, I may ask for a 9x12" print, or a file I can use to make a 9x12" print from.  If I can't get that from the photographer, I likely won't be working with him or her again for portfolio work.

To avoid the printer doing any cropping you may not like, perhaps crop the images on your own (in a duplicate file, of course) before sending them to the print shop.  Or you can add a border on the image to make it 9x12" without cropping.  Black or white.

And, of course, any prints or files to be printed from should be free of watermarks or credits on the front.

ETA: To clarify, if I were to receive an 8x10" or 8x12" photo printed with borders on 9x12" paper, that would be acceptable.  But I don't want smaller sized prints floating around sloppily inside the pages.  I don't want my print book looking sloppy--that makes a worse impression, I imagine, than prints with borders.

Since I'm working on a printed portfolio myself, I thought I'd give you what I'd learned:

The fashion/commercial 'standard' is an 11x14 book. It can be any variety of papers, full bleed or bordered, as long as the book size is 11x14.

An 11x14 book allows the art director/buyer/agency to see that you do indeed have the original files (I.E: Not ripping them from someone else) and that you (or your print house) can turn out a decent print at a reasonable size. Prints are unforgiving, so they like to see the perfection large.

As to the 8x12, you could try printing one book at that size and then tote it around. Try to get feedback about whether they like it at that size or not. Everybody has an opinion so the best way might be to simply run with it.

This is becoming less and less relevant as people migrate to tablets for portfolio presentation.

crop for the needed ratio (3:4 for 9x12) or keep the original aspect and bleed to the short side with black gutters

I have often wondered why 8.5x11 is not used more.  Seems like a good all around compromise, readily available, and common.  I guess traditions die hard.  But, as has been said, the ipad is changing all of that.

Thanks for all of the replies. Most of my shoots are TFCD, but I may want to offer some TFP work just as an incentive for some. So that's how my question originated. Good replies. Thanks.