Earl Dunbar wrote:
>
> That is intriguing, especially since there is no 70mm OM system lens
> (outside of zooms), i.e. it's an interesting focal length on the E-1.
> Not sure it would be something I'd use a lot, but yesterday I was at a
> wedding and put the 100mm on the OM-1n to do some casual
> head-and-shoulders isolation shots of guests during the reception. It
> was a bit too long for some shots. Yes, I could have moved back, but
> these were quick grab shots, and I would have missed the shot. I often
> find myself wanting a prime in the 65-80mm range. Even when I had an M3
> with a 90, I was often wishing for a 75mm.
---------------------------------------------------
I've always wondered why the 70mm prime seems to be missing from most
35mm camera systems. The focal length of many primes seem to be based
on a system of doubling the area of coverage from one to the other.
This leads to ratios of the square root of 2 (1.4) between them.
From 400mm on down we should have:
400, 280, 200, 140, 100, 70, 50, 35, 25, 17.5, but usually have:
300 135 85-90 24 17-18
Percentage wise, the difference between 135 and 140 or even between 280
and 300 isn't too large but the gap from 50 to 85 or 90 is very large.
I suppose the rules say we should do portraits with 85mm lenses on 35mm
film so, having to provide an 85mm may just be too close to 70 to
properly complete the sequence.
Anybody know what the historical accidents are that led the the
"standard" set of prime lens focal lengths? And how did the Minolta and
other 58mm standard lenses get in the mix? An attempt to bridge the gap
between 35 and 85?
Chuck Norcutt
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