curl@wjvax.UUCP (Jim Curl) (12/14/85)
I own a Minolta X700 camera and am shopping around for a zoom lens with
a wide range. I know that at least three manufacturers produce a
35-200mm zoom, Vivitar, Tokina, and Cosina. Of the three, Cosina's is
the most compact and the most expensive.
Has anyone out there had any experiences with these (or others) or read
about them? I'm curious to know what the tradeoffs are between the lenses
in terms of optical quality, compactness, maximum aperature, etc. For
instance, I wonder if the Cosina lens, as a result of its small size,
loses something in the extremes of zoom and focus.
Answer via mail or by posting a response.
Thanks,
Jim Curl
San Jose, CAmather@uicsl.UUCP (12/15/85)
Zoom lens suffer from 3 problems: 1) weight (more elements needed for the range of focal lengths) 2) distortion (caused by the added lens groups) 3) speed (they are typically a few stops slower than tele's) However, the newer designs have really made an impact in all 3 of these areas. They lens designers are now pushing those optics programs (FORTRAN?) to design V E R Y W I D E A N G L E lens which are light, fast and clear. I haven't bought any of these ultra-wides, but have read that the weight problem still exists and you may find the focus-zoom feature annoying. 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. ---- b.c.mather Software Surgeon uiucdcs!uicsl!mather
kanner@tymix.UUCP (Herb Kanner) (12/19/85)
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. ...!hplabs!oliveb!tymix!kanner
seifert@hammer.UUCP (Snoopy) (12/19/85)
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. Sounds like the 28-90 is NOT a zoom lens. A zoom lens does stay in focus throughout the focal length range. This is essential for motion picture cameras, and for some still applications. Not everyone requires a true zoom, so they make non-zoom variable focal length lenses, which can then be lighter, smaller or cheaper, since they have one less design constraint. I think there's a special term like "veri-focal" for them. Snoopy tektronix!tekecs!doghouse.TEK!snoopy