Comments below.
At 8:57 AM +0000 11/28/02, olympus-digest wrote:
>Date: Wed, 27 Nov 2002 18:33:30 -0800
>From: dreammoose <dreammoose@xxxxxxxxx>
>Subject: Re: [OM] Mind Bender (intermediate focal length?)
>
>In the focal length series I calculated based on FOV, I used the
>theoretical FOV, calculated using simply focal length and film width.
This approach does have the advantage of largely eliminating the effects of
lens design.
>Moose
>
>Joe Gwinn wrote:
>
> >The problem is that field of view varies from lens design to lens design,
> >even if the focal length is the same, so using FOV values to determine
> >something like "intermediate" is only approximate.
> >
I was thinking also of the lenses used on view cameras, where the field of view
(that is, image circle) vastly exceeds the film size. Ditto, shift lenses for
35mm. So, I was looking for an algorithm that included only data that was true
of all lenses, regardless of design, which leaves only focal length.
Anyway, we have two answers, 141.4mm (~140mm) and 135mm. I don't think it much
matters which answer one uses:
140/100= 1.400
200/140= 1.429
1.429/1.400= 1.020
135/100= 1.350
200/135= 1.481
1.481/1.350= 1.097
And of course, 140/135= 1.037
So, we are within 40f each other, far too small a difference to be
photographically significant. At this point, the question will devolve to a
question of optical quality of the actual lenses in question. We can even
debate relative bokeh, if we have the energy.
Joe Gwinn
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