Archived posting to the Leica Users Group, 2001/03/25

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Subject: Re: [Leica] lens equivalences (was Rolly 3.5f)
From: Johnny Deadman <>
Date: Sun, 25 Mar 2001 17:28:51 -0500

on 3/25/01 4:17 PM, Dave Jenkins at wrote:

> Doug, wonderful though both the 75mm Xenotars and Planars are, they are
> actually equal to a 49mm lens on a 35mm camera *in side to side*
> coverage. The commonly used diagonal measurement of coverage is
> confusing because it can only be valid if the frames are the same shape.
> Otherwise, you're comparing apples and oranges.

I went into this a while ago for my own satisfaction and really there are
three different ways of looking at equivalences and none of them are really
satisfactory. You can look at the short side, long side or diagonal. So for
example a 75mm lens on 6x6 can be considered equivalent to a 110mm, 135mm or
even 150mm on 4x5 depending on which side you choose to compare. Whichever
one you choose it still never looks the same on a different aspect ratio.

Certainly the 75mm Xenotar FEELS a lot wider than a 49mm on 35. I'd say the
41mm equivalence reflects my own experience. But like I say there are no
'right' answers to this one.
- -- 
Johnny Deadman