It is _not_ the same proportion: A 35mm negative is 24mm x 36mm, a
ratio of  1.5:1 where 8x10 is 1.25:1, so one is either going to get
wide boders along the long dimension if it is fitted to the paper,  or
you must crop the long dimension to get the short dimension to fit.
AFAIK, there is no paper of the right aspect ratio for standard 35mm
double frames. There is no law against trimming paper to whatever
dimensions one desires.
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com

I missed the last part. The lens makes no difference whatever
whether its the camera lens or enlarging lens. Its just a mis-match in
the shape of the negative and printing paper.
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com

I often print 35mm and 6x9 negatives (same aspect ratio) to approximately
7x10 on 8x10 paper.  You can even get artsy, file out your negative carrier
and print those little black edges so beloved by some and hated by others.
You can go further and print exactly 6x9 on 7x10 and leave borders all
around the image.

Note that 6x6 negatives will print 8x8 inches and that the so-called ideal
formats 645 and 6x7, while close, do not enlarge to exactly 8x10 either.
And our standard print sizes (US anyway) 3.5 x5, 4x6, 5x7, 8x10, 11x14 all
have different aspect ratios.

Since most camera viewfinders do not show 100% of the film image, and most
enlarger carriers do no reveal 100% of the film image on projection, we all
crop a little when printing, can't be helped, and most images can benefit
from a little (or a lot!) of cropping.

Cameras than have 100% viewfinders that I am familiar with:  Nikon F, Nikon
F2 (others?--read your manual!), most other makers argue that slide mounts
and prints are cropped and that the extra effort is not worth the expense to
create and align a 100% viewfinder.

The few that insist on seeing 100% of every image they shoot since they
spent the time to compose the shot in this exact fashion, etc. etc. are the
bane of photofinishers everywhere and have a cult reputation similar in many
ways to the Zone group.  Slow painstaking composition is contrary to mission
and purpose of a small candid 35mm camera or a motor drive camera for action
shots.  No reason it cannot be done, but if you propose to work that way, be
prepared to mount your own slides in special mounts or print your own
images, you'll never be satisfied with commercial lab work.

Most enlargers can project 100% images using either glass carriers or
carriers that have been filed out to 100% (or more).  There are pros and
cons to this approach, which I don't feel like getting into right now.

BTW, right after WW2 the Japanese were make 35mm cameras with an "ideal"
format (24x30 or 24x32--I don't remember which) but the US (which was still
in charge in occupied Japan) made them change to the more common 24x36 so
that their offerings would be more marketable in the US and elsewhere and
bring home some much needed revenue.