[15 / 2 / ?]
Two things.
A. Why did so many companies make 135mm f/3.5 lenses during the film days? I saw Canon, Nikon, Olympus, Pentax, minolta and Zeiss (and konica soligor?) all produced 135mm f/3.5 lenses back in the pre EF mount film days.
B. why do we always base crop factors on the diagonal instead of the vertical for different aspect ratios? The olympus 75mm f/1.8 is a weird 150mm based on the diagonal, but if you take the vertical its a pretty normal 138mm (most lenses aren't exactly the focal length they say) f/3.5 like the old film lenses. Same as the pentax 645 150mm, which is a 93mm on the diagonal but an 86.5mm vertical. so both lenses look more like a 135mm or 85mm that you cropped the sides off to make an 8x10
A. Why did so many companies make 135mm f/3.5 lenses during the film days? I saw Canon, Nikon, Olympus, Pentax, minolta and Zeiss (and konica soligor?) all produced 135mm f/3.5 lenses back in the pre EF mount film days.
B. why do we always base crop factors on the diagonal instead of the vertical for different aspect ratios? The olympus 75mm f/1.8 is a weird 150mm based on the diagonal, but if you take the vertical its a pretty normal 138mm (most lenses aren't exactly the focal length they say) f/3.5 like the old film lenses. Same as the pentax 645 150mm, which is a 93mm on the diagonal but an 86.5mm vertical. so both lenses look more like a 135mm or 85mm that you cropped the sides off to make an 8x10
