Originally posted by pacerr This may be a chicken-and-egg argument, and I'll not repeat the often voiced point about 50mm being the normal FOV for normal people at a normal viewing distance, but I've read more than one presumably knowledgeable person that noted that the 50-55mm focal length is the easiest FL to design and manufacture a fast lens for in the 135 format.
I haven't seen proof of that, but the preponderance of excellent, low(er) cost 50's in all brands would seem to support that view.
Could just be 'cause 50mm is normal, but I'd think there'd be some strong marketing ploys if there was an alternative FL.
H2
Well, sorta.
43mm's normal on a 35mm cameras (it's why the FA 43 is what it is.) 45mm would be much more logical, I suppose.
Thing is, it's actually a bit easy to design telephotos, especially with SLRs. A lot of telephoto primes have less elements than 50mm, and are still of comparable quality.
Back when the 35mm camera system kicked off with Ur-Leica, the bloke who designed it, Oskar Barnack, decided on a 50mm lens as a standard, although they weren't thought of as "standard" back then. Why? Who knows. It became standard, after a while. Although I haven't looked into, Barnack probably got the lens formula from Zeiss, who're responsible for a shedload of optical innovation - Tessar, Sonnar, Planar for starters, which were widely copied, with good reason. Most fifties are based on the Zeiss Planar - a design dating from 1896 - including Pentax's.
Basically, manufacturers started...not quite
copying, but certainly using the principles Barnack had developed, and it was just easier, and anyway 50mm on 35mm film's a pretty good length.
So, 50mm lenses are what lensmakers got good at. The kinks got worked out early (the FA 1.4 50mm is optically identical to the 1976 K 1.4 50mm - in fact, none of the later Pentax fifties differ from their earlier counterparts, save for number of aperture blades.) They're small, and their perspective makes it easier for people to compose a shot, as looking through the viewfinder with a 50-odd millimetre lens on it doesn't shock you with a whole bunch of extra stuff outside of your main field of view.
You don't need a lot of glass to make 'em fast, either. An f1.4 50mm needs only a slightly curved front element 35mm in diameter.
Now, since, back in the day, since this was a standard lens everyone expected a camera to have, the fifties were the kit lenses. Every camera came with one (you could probably pick between a cheaper, slower one, or a more expensive, faster one. I wasn't there.)
That's why they tend to be cheap, yet well done. They're easy to make, because all the research and design has been done, and more importantly, has been pretty much perfected. There're a lot of them, keeping down the price, because they were a nice practical focal length and sold with pretty much every camera up until the eighties.
As for whether it's a good standard lens, that's a matter of choice. Some swear by 40mm, some by 35mm. The term "standard" or "normal" really only applies to the "standard" lens you "normally" shoot with.