Mamiya 645 Lens on Canon EOS Camera

Started Sep 29, 2009 | Discussions thread
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(unknown member) Senior Member • Posts: 5,590
Re: Mamiya 645 Lens on Canon EOS Camera

Ray UK wrote:

The crop factor confusion has been well discussed above so I won't comment further on that, however I have seen various discussions in manual focus forums relating to the use of medium format lenses on 35mm or crop cameras and the general consensus seems to be that they are not that good.

The theory being that they do not have the resolving power compared to a lens that has been designed for the smaller format because the design of the lens needs to take into account the larger image circle and some of the centre sharpness has been sacrificed in trying to achieve this larger coverage. On a medium format camera this slight loss wouldn't be noticed because you don't need to enlarge a medium format image quite so much to get a decent sized picture.

How much truth there is in this, I do not know, but in theory it does seem to make sense.

Essentially you are correct in saying that the resolution of 6x6 format lenses is generally not quite as high as the best lenses designed for smaller formats.  Having said that many 6x6 format lenses were of good optical quality, so whilst they might not have quite the resolution of a state of the art lens designed for for 35mm, the resolution that they do have tends to hold up right to edges of a 35mm frame and also evenness of illumination across the frame can be excellent because only light rays transmitted from the centre of the lens are being used on a smaller format.

If you already have such lenses then there is no reason not to give them a try but I'm not sure it is really worth spending too much money on an adapter bearing in the mind the totally manual operation of such lenses and the fact that you are carrying around a much heavier and larger lens than one specifically designed for the smaller format.

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