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Re: [OM] Zuiko zooms barrel distortion tests

Subject: Re: [OM] Zuiko zooms barrel distortion tests
From: "John Prosper" <japrosper@xxxxxxxxxxx>
Date: Mon, 18 Jun 2001 09:05:26 -0500
From: "Olaf Greve" <o.greve@xxxxxxx>

Hi,

Good, I just received the results of my comparison shots to test for the
various types of distortion in the Zuiko zooms, so it's time to add some
more fuel to the fire:

The tests performed (all at f5.6, and roughly at some 5M distance from the
wall, shutter speed varied between 1/15th and 1/30th seconds):
-35/2.8 Shift (neutral position): slight barrel distortion.
-35-70/3.6 @ 35mm: slight to moderate barrel distortion.
-35-70/3.6 @ +/- 40mm: slight barrel distortion.
-35-70/3.6 @ 70mm: slight pin cushion distortion.
-35-80/2.8 @ 35mm: slight to moderate barrel distortion (hardly more than
the 35-70/3.6!).
-35-80/2.8 @ +/- 40mm: very slight barrel or wave-form distortion.
-35-80/2.8 @ 80mm: slight pin cushion distortion.

{Material deleted}

So, in my opinion, the 35-80/2.8 owners can sleep again; no need to think
that a HUGE gain in distortion elimination will be had by using the Shift
lens. ;)

I am not in the least bit surprised by your findings. I owned the Zuiko 35-70/3.6, and it has been the sharpest zoom I have ever possessed, producing 8x12" enlargements indistinguishable from same photo session output from my 90/2 macro. I sold it for its one major failing?lack of real speed?and I plan to add a 35-80/2.8 later on. I was never bothered by the barrel distortion of the 35-70/3.6, but then I never employed it when framing images where linear precision was required.

Distortion in standard zooms (or any! zooms for that matter) is quite common especially at the wide-angle end. I never understood all the excitement from those complaining about distortion in such a pricey zoom. The high-end units from Nikon, Canon, Pentax, Leica, Minolta, and Contax exhibit similar distortion. It is merely one of the realities of the design tradeoffs in making such a complicated lens unit.

If one requires absolutely straight lines across the frame, one should use a prime lens, especially a perspective control lens (although the 35/2.8 PC wasn?t quite perfect either)?not a zoom. Zooms are general-purpose optics with reasonable geometric precision: they are not the preferred critical choice when perfect linear precision is required.

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