With the larger negative size the field of view of medium format lenses is much wider than the field of view with the same focal length on 35mm. To make a comparison with 35mm film SLR fields of view multiply the focal length by 0.48. For instance, 90mm is ~44mm in 35 film SLR terms.
I do not see a consensus on which lens series is the best. The non-C single anti-reflective coating lenses seem to be the “worst”, but the optical difference between the K/L and C lenses is not so clear. Some commentators have indicated that the C series had poor quality control, whereas the K/L lenses–being optically the same–are better by virtue of better quality control.
Single anti-reflective coated lenses released in 1970 with the original Pro
These lenses are optically identical to the original lenses, but have a newer barrel design (NB) that matches the later C lenses. They only were produced briefly and are comparatively rare on the market.
C, apparently, stands for “Design Improvement”. These lenses are multi-coated. Released with the Pro-S in 1974. Has a “C” on the front name ring.
Most recent. These lenses are, apparently, a slightly newer design with better coatings than the C lenses. The K/L is a code to indicate which bodies the lenses are compatible with. K indicates the Pro/Pro-S bodies and L indicates the Pro-SD bodies. KL lenses all shipped with an adapter attached to the lens so that they can be mounted to Pro-SD bodies. This adapter should be removed to mount to Pro/Pro-S bodies. This adapter is a fairly simple rubber O-ring for light sealing rather than for any mechanical reason. I, personally, have not had any issues using C lenses on my Pro-SD body without the small adapter ring.
Has a “K/L” on front of the barrel.
Compatible with Pro-SD *only*; these are the 75mm Shift lens and 500mm APO only.
Apochromatically corrected lenses. Sometimes known as A lens. More expensive, heavier, but chromatic aberrations are better corrected.
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|Length (mm)||Maximum Aperture||Generation||Angle of View (in degrees)||Weight (g)||Details||Notes|
|65||f4||K/L||68||1070||Details||This is a new, different optical design than the earlier original and C 65mm lenses|
|140||f4.5||C||36||800||Details||Macro lenses with floating element to adjust plane of focus curvature.|
|150||f4||C||33||790||Details||Soft focus lens|
|210||f4.5||APO/L||24||1020||More details||Apochromatic correction|
|250||f4.5||APO/L||21||1370||More details||Apochromatic correction|
Auto Extension Tubes
Two extension tubes–for use in close up photography–were produced, the No. 1 (45mm) and No. 2 (82mm).
Extension tubes were produced for the Pro and Pro-S and a different model for the Pro-SD. The Pro-SD extension tubes fit the larger lens throat of the Pro-SD body. Because of this the Pro-SD extension tubes do not fit on Pro or Pro-S bodies.
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DiSante, T. (1981). How to Select & Use Medium-Format Cameras. HP photobooks. Tucson, AZ: H.P. Books.