Nikon 50mm vs Mamiya 90mm

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I made an interesting experiment : I shot with nikon 50mm f/1.4 lens and mamiya 90mm f/3.5 KL lens, to proof that medium format should deliver sharper image, because of less magnification needed from medium format to produce same size of photos (8x10" photos is magnified 3,5x from 6x7cm negative and 8,3x from 35mm) I shot with same aperture f/4 I should actually compare lenses that produced from the same manufacturer (carl zeiss : hasselblad / rollei vs contax), but due to equipments limitation, I compare mamiya vs nikon. photo from medium format is sharper (of course), the most interesting thing is that the photo taken with mamiya lens shows blur on the corners, while nikon lens shows sharp image on the entire photo. My question is : is the depth of field at same aperture and at 'same normal lens' different between medium format and 35mm ? or is mamiya lens that bad ? Could anybody explain please ?

Thank you

-- Erick (eik@bdg.centrin.net.id), April 02, 2002

Answers

You guessed it: depth of field is different. Depth of field is a function of absolute aperture (the working diameter of the lens) rather than relative aperture (f/number), so a 90mm lens at f/4 would have a depth of field closer to that of a 50mm at f/2.

This is one of the big reasons why the 35mm format became so popular back in ancient times, the increased depth of field was a big factor in the development of faster lenses in the smaller format.

rick :)=

rick_oleson.tripod.com

-- rick oleson (rick_oleson@yahoo.com), April 03, 2002.


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