Medium format lens to 35mm and calculations...

Flor27 · Joined: 13 Sep 2007 Posts: 1195 Location: Paris, France

Hi,

I would like to know how to calculate the resulting focale lengh and angle of view if I feet a medium format lens to my 35mm camera. I'm not aware in photographic mathematics actually Embarassed

Thanks !

Laurence · Expire: 2016-06-19

rick_oleson · Posted: Thu Nov 15, 2007 3:11 am Post subject:

Since the proportions are different, there is no exact "right" answer. Probably the easiest way to get into the ballpark is to look at the normal lens on your MF camera and divide that by 50mm to get a correction factor: if you have an 80mm normal on a 6x6 camera, for example, the factor would then be 1.6 (80/50).

The optician's way is to measure the diagonal of the negative and use that as the standard: 6x6 cameras often are actually closer to 56mm square; the diagonal of that is 80mm. 35mm is 24x36, the diagonal of which is 43mm.... so if you use that method, the correction factor is 80/43, or almost 1.9. But, you use the whole 80mm only if you print square format prints, if you crop them down for 8x10s or whatever, you're back closer to the 1.6 calculated above.

There are other ways to look at it too: if you use both cameras for square prints, then you're only getting 24mm square on the 35mm negative, so that makes it 80/34 or 2.4. Or, if you use both cameras for 8x10 format prints, you're using 24x30 on the 35mm and 45x56 on the MF... that gives you 72/38 or a 1.9 correction factor.

That last one may actually be the closest to reality for most people.

rick_oleson · Posted: Thu Nov 15, 2007 3:15 am Post subject:

Looking at your question again, I think there might be a little extra confusion:

If you're familiar with the 35mm format, and you fit, say, an 80mm medium format lens onto your 35mm camera with an adapter, the 80mm MF lens will perform just like an 80mm short tele made for the 35mm camera. In that sense, there is no 'crop factor' involved; the medium format lens will behave exactly as its marked focal length indicates.

Laurence · Expire: 2016-06-19

rick_oleson · Posted: Thu Nov 15, 2007 4:27 am Post subject:

Those are all of the lenses that I have adapters to use on my Canon DSLR.... 43 in all, I think. I don't think I've actually USED them all on it....

Laurence · Expire: 2016-06-19

rick_oleson · Posted: Thu Nov 15, 2007 11:37 am Post subject:

there is a down side: you need a cabinet the size of a barracks to keep them in.....

: ) =