The M9 theme stretching thumbnails for vertical images. I've tried searching around a little to see what all is involved in fixing this. I've seen a little about adding a custom thumbnail function, but don't quite understand where to start. Can anyone help me, or at least point me in the right direction.

In album.php find
echo getCustomSizedImageThumbMaxSpace($width="298", $height="187");

and change it to

echo getCustomImageURL( NULL, 298, 187, 298, 187 );

This will crop the thumbs for vertical images.
If the thumbs are not cropped, the layout and hover effect will break.

Wow! You just made my day! It worked! Thank you so much... I thought for sure I wouldn't get a reply. Much appreciated.

*As a note, I notice the thumbnails now contain my watermark. Is this because instead of generating thumbnails, now the thumbnails simply call on the actual image? Either way, really glad to get rid of those funky stretched thumbanails!

Quote: Is this because instead of generating thumbnails, now the thumbnails simply call on the actual image?
That's correct :-)

If you like to remove the watermark change:
echo getCustomImageURL( NULL, 298, 187, 298, 187 );
to
echo getCustomImageURL( NULL, 298, 187, 298, 187, NULL, NULL, true );
It is then treated as a "thumbnail" which does not have a watermark.

Btw, we always try to answer to questions ;-)

Brilliant! Absolutely brilliant! It's perfect. Thank both of you so much for your help! I couldn't find this solution when I was searching. Has it come up before? I'm still surprised at how swiftly and deftly it was answered!

It is known and not direclty noted on the user guide because it is documented on the main technical documentation:
http://www.zenphoto.org/documentation/elementindex.html