Medium Format Family

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6x6 to 35mm real lens equivalent?


Hi guys, I'm finding a bit of difficulty trying to come with a lens equivalent from 6x6 to 35mm,

what is the conversion ratio? It is not simple because the hasselblad medium format image is square!

I know if you shoot 6x4.5 you can use 1.5 as your conversion ratio, making a 75mm lens equivalent to a 50mm.

so: lets say I want to frame the same "landscape" that I am now framing with a 50mm hasselblad lens on 35mm film format, which focal length lens should I use on 35mm film?

making the question even more difficult, lets assume I am going to crop the 35mm film capture into a square. which lens will give me the same view point (after cropping it to a square) that I get from the 50mm hasselblad?.

Thanks a lot


New Member
This is not a simple matter as it might seem.
To compare the effect of focal lengths between various format you should be comparing the angle of view.

In 35 mm the accepted standard focal length is 50 mm.
With 6x6 the standard focal length is 80 mm.
That gives a ratio of 1.6 between those formats.
35 mm images reduced to square formatare 24x24 mm
That gives a ratio of 2,35 compared to 6x6 format.

The accepted standard focal length for 35 mm format film is 50 mm when in fact it should be 43 mm.
The standard focal lenth for 6x4.5 is 75 mm when in fact it should be 70 mm.
Generaly a standard lens is a little longer than the theoretic value.
the way I "convert" is as follows:

6x6 ---> 35mm equivalent
40mm --> 24mm
50mm --> 28mm
60mm --> 35mm
80mm --> 50mm
120mm -> 75mm
150mm -> 85mm
180mm -> 105mm
250mm -> 135mm

Of course your mileage may vary and I could be totally off base, but it seems to work for me.