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From: kanner@tymix.UUCP (Herb Kanner)
Newsgroups: net.rec.photo
Subject: Re: Zoom lens comparisons
Message-ID: <599@tymix.UUCP>
Date: Wed, 18-Dec-85 21:59:55 EST
Article-I.D.: tymix.599
Posted: Wed Dec 18 21:59:55 1985
Date-Received: Fri, 20-Dec-85 05:14:57 EST
References: <632@wjvax.wjvax.UUCP> <11900005@uicsl>
Reply-To: kanner@tymix.UUCP (Herb Kanner)
Organization: Tymnet Inc., Cupertino CA
Lines: 19

In article <11900005@uicsl> mather@uicsl.UUCP writes:
>
>I bought the Vivitar Series I 28-90 f2.8-3.5  and the lens does NOT stay
>in focus as you zoom. This is typical of fast zooms, but I find it a pain
>compared to my Vivitar Series I 70-210 f2.8-4.0 which I can focus at the
>farthest focal length (210) and then zoom back for optical framing.
>I personally still opt for two zooms of slightly overlapping range.
>----
The 70-210 is a zoom lens.  The 28-90 is NOT a zoom lens; it is a
vari-focal lens and is so designated by Vivitar.  Of course, camera store
advertisements might mis-name it.  I assume that by giving up the
characteristic of staying in focus as you change focal length they achieved
some gains elsewhere in the design, e.g., fewer elements or better
correction of aberrations.  

-- 
Herb Kanner
Tymnet, Inc.
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