Why Medium Format lenses are not as fast as 35mm?

[benjiboy]

So True. The f/3.5 aperture on my 80mm lens has very little DOF wild open. I would not open it up much more if it were able to as the DOF would be almost nothing!

That's another factor that I haven't mentioned Ratty. and one of the reasons for the initial and continuing popularity of 35mm, that equivalent focal length lenses to medium format ones that aperture for aperture they give much more depth of field therefore can be much faster and still produce enough sharpness in depth to shoot in low light conditions.

 

[JOR]

A 50mm f/2 lens will have a hole 25mm (1") in diameter. The hole in an 80mm f/2.8 lens will be 26.7mm in diameter. If both lenses have the same number of elements the manufacturing cost will be similar. Until medium-format cameras had reliable focal-plane shutters, the diaphragm hole diameter was typically limited by the weight (and therefore inertia) of the leaf shutter blades. The maximum speed was limited to 1/300, later 1/500sec. Thus lenses for Mamiya RZ, Hasselblad V series, Fuji GX etc had modest maximum apertures.

Many years ago I worked on a processor for 10" wide aerial reconnaissance film. I once glimpsed an aerial camera as it was being taken from the aircraft. From memory, I estimate that the front element of the lens was about 6" (150mm) in diameter and the whole camera, including the motorised film back, was about 4ft (1.2m) long. So the maximum aperture was about f/8. I hate to think of the price!