Calling Leica historians: the 5cm normal lens, etc.

Was Leica the first to use a "normal" lens in 5cm for the 135 format?

Any particular reason why this focal length was chosen instead of

other nice round numbers like 40 or 45mm, both being closer to the

format's diagonal length?

 

Other focal lengths like 135, 35 and 28mm also became "standard

offerings" across brands (e.g. Zeiss) right from the beginning, AFAIK.

Why is that? No such "agreement" among makers WRT to short teles -

we had 85, 90, 100 and 105mm.

The 50mm lens was in common use at the time as the "standard" lens for the standard 35mm motion picture format, 18x24mm. This format was doubled to 24x36mm in the Leica. It had little to do with matching the diagonal of the movie frame. Movie makers seemed to like the flatter perspective of the slightly narrower angle of view.

 

90mm was already in use as a normal lens for 6.5x9cm format and 135mm for 9x12cm. I suspect that the standardization of the wide angles (28 and 35) was to match the viewfinder optics in movie cameras of the day.

Leica was very nearly the first to use the 135 format for still photos anyway.

 

I don't think the diagonal of the film plane has ever had much to do with the decision on standard lenses, but has been used frequently as a rationalization after the fact to "explain" the normal focal lengths, when the real explanation is some combination of history, what's easy to make and what looks reasonably normal. The 50mm must be said to have proved itself worthy according to those criteria.

 

Using slightly longer normal focal lengths (which the 50mm effectively is) in movies makes sense, as moving the camera - or the subjects - make the "distorting" effects of wider angles more visible.

Given that the Leica was originally to be marketed as a device for testing movie films, I think Al's explanation is probably closest to the mark.

http://corsopolaris.net/supercameras/early_135.html Interesting web page on early 35mm cameras...

I read somewhere that the Ur-Leica had a 43mm f/4.5 lens.

One of our members (I think it might have been Albert Knapp) told us that the focal length of the human eye is, I think he said, 42mm. And the film diagonal for 135 format is 43mm. These two facts would seem to suggest that 42 or 43mm would be the most natural choice for the format. I imagine that might be what Contax was thinking when they settled on a 45mm normal lens. I've also wondered if this is what Nikon had in mind when they chose the lower zoom limit of their old 43-86mm optic. Currently, I believe they have added a 45mm Tessar-type lens.

 

When we print our negatives to a 4x5 or 8x10 proportion, we are only using 24x30mm of the negative. In that case, the diagonal becomes 38mm. Considering all of the above, it's not hard to see why some of our members consider the 40mm Summicron to be the best all-around lens.