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Path: utzoo!watmath!clyde!floyd!harpo!seismo!hao!cires!nbires!opus!rcd
From: rcd@opus.UUCP
Newsgroups: net.rec.photo
Subject: Re: recomendations?
Message-ID: <269@opus.UUCP>
Date: Sat, 24-Mar-84 02:39:04 EST
Article-I.D.: opus.269
Posted: Sat Mar 24 02:39:04 1984
Date-Received: Sun, 25-Mar-84 13:41:44 EST
References: hpfclk.90500001 <261@wxlvax.UUCP>
Organization: NBI, Boulder
Lines: 36

<>
> As to lenses.  What is quality?  If I am after large enlargements, I will
> either use a medium format (Rolli TLR) or a 4x5 if I can carry it...
In general, there's a good point here - the resolution limit of a
mediocre lens, open wide, off axis, is in the same neighborhood as 
the resolution of typical film.  Still, if you're working to 8x10, the
difference between mediocre and good lenses will be noticeable,
particularly with zooms.

>...I not only looked at the quality of the optics,
> but the weight.  In the end, the latter was as important for two reasons:
> 
>    1. The weight of a heavy lens can distort the optical position of the 
>       mount on the camera.  It may not be parallel with the film plane.  This 
>       can reduce the quality of the photographs.
Most manufacturers are aware of this possibility, but it isn't a
significant phenomenon until you get a really heavy lens.  The error in
lens position due to lens mount distortion will be less than the error due
to incorrect focusing.  When the lens gets really big, you will find that
the lens body has (or should have) a tripod mount built into it - thus you
mount the camera to the lens rather than the reverse.  This also provides a
guide to where the break-even point occurs for too much weight for the lens
mount - the mount can easily support the weight of the camera without any
appreciable flexing.  (Try a Questar with a 35mm camera sometime.)
> 
>    2. If you want to handhold the camera, you would want a light lens.
No.  The weight works both ways here:  If the lens is so heavy that it
makes your hands shake, then yes, you need a lighter one.  Otherwise, the
mass of the lens helps steady it - for a given force from your hand, the
lens won't wiggle as far.
If you use the lens on a tripod, the length of the lens can be a factor.
Some lens designs give an overall length approximately the same as the
focal length; some are much shorter.  If there is a significant difference,
the shorter lens will be more stable on a tripod.
-- 
{hao,ucbvax,allegra}!nbires!rcd