Funny you should say that. Nominal 6x9 is more or less 56 x 81, whence its normal focal length is 100 mm. Slightly longer tessar types were used on 6x9 folders to improve image quality in the corners a little. 35 mm still is 24 x 36, whence its normal focal length is 43 mm. That 35 mm cameras are usually supplied with 50 mm lenses is due to an historical accident.
Originally Posted by 250swb
The two formats have the same aspect ratio, so comparisons between them are easily made. A 90 mm on a 2x3 (nominal 6x9 is actually 2.25" x3.25", usually called 2x3; 6x9 is a lousy metric approximation) is sees the same view as a (90/100)*43 = 39 on 35 mm still. A 180 on 2x3 sees the same view as 1.8 * 43 = 77 on 35 mm still. Short verging on medium tele, I'd say.
105 was the mfg "norm" for both taking and enlarging lenses per 6x9. For example, Both Fuji and Nikon
make 105 plastmats, and I personally own one of the relatively rare 105 Nikkor M tessars. But what is
"normal" to your personal way of looking at things is a completely different issue. I mostly use 85mm
with my Nikon 35mm camera, a 165 with 6x7, 180 or 200 with 6x9, 250 with 4X5, 450 with 8X10;
in other words, all these have an analogous angle of view which is natural for me. Someone else might
have a completely different notion of first base. Strictly defined, normal is equal to the diagonal of the
film; but who gives a damn?