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[OM] Re: Fisheye confusion - Resend - additions and correction, please i

Subject: [OM] Re: Fisheye confusion - Resend - additions and correction, please ignore previous version.
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Tue, 15 Nov 2005 22:53:22 -0800
Dan Mitchell wrote:

>So, on an E-1, the 16mm fisheye wouldn't get me anything over the 
>14-54 except for some possibly interesting distortion, 
>
It's not as simple as all that.

First, there are variations from sample to sample. Plus or minus 5% 
seems to be a normally accepted standard. For example, here are some 
results from Modern Photography tests.

              Spec.        AOV     Meas.    AOV    FL var.
Zuiko         18/3.5      100.5    18.76    98.1    +4.2%
Zuiko         21/2         91.7    20.15    94.1    -4.0
Tamron        17/3.5      103.7    17.75    101.3   +4.4
Samyang     18-28/4-4.5   100.5    17.81    101.1   -1.1
Vivitar S1  19-35/3.5-4.5  97.4    19.1      97.1   +0.5

Now I believe that Oly intended their lenses to be as specified and the 
fact that this particular 18mm was 4% long and the 21mm was 4% short was 
normal sample variation from imperfect manufacturing.

But notice what this says about making all sorts of assumptions about 
different lenses of similar nominal fls. The particular 17mm Tamron and 
the 18mm Samyang tested are for all reasonable purposes, identical in 
focal length.

Second, there are the great differences between rectilinear and fisheye 
lenses. A rectilinear 16mm would cover about 59 deg. horizontally on 
4/3, while the 16 fisheye would cover about 78 deg, equivalent to an 11mm 
rectilinear lens.

>and even on 35mm film, compared to the existing 17mm lens I have, it wouldn't 
>get me much more.
>
A rectilinear 16mm would cover about 97 deg. horizontally (107 
diagonally) on 35mm, while the 16 fisheye would cover about 163 deg. 
(180 diagonally) Quite a considerable difference!

Do you happen to have one of the Zuiko Interchangeable Lens Group 
Booklets? The samples on the inside front cover fold-out and the inside 
back cover are quite useful visual guides to lens coverage. The 
landscape coverage of the 16mm is much greater than the 18mm.

Moose


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