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Re: [OM] Distortion in 35/2.8?

Subject: Re: [OM] Distortion in 35/2.8?
From: "L.J. Clark" <ljclark@xxxxxxxxxxxxx>
Date: Tue, 20 Jan 1998 18:38:30 -0800
Some on this list have described what you experienced as "barrel
distortion".  I'd be a little cautious with that diagnosis.

If you have barrel distortion, it will show up when you photograph
a grid when the film plane and subject are parallel.  The lines will
be curved (bulging outward).

Your lens may very well have barrel distortion, but it is much
more difficult to quantify this if you tilt the camera off axis.

The distortion can vary through the focus range.  You can also
complicate things by introducing a little distortion from your
enlarger lens.  Likewise, you can't tell by looking through
the viewfinder.

Shawn Wright wrote:
> 
> I just printed an 8x10 shot with my Zuiko 35/2.8 (single coated), 
> with an old church near the centre, and three old lamp posts, one 
> near the centre, and one near each edge of the frame. Upon printing, 
> I noticed the outer lamp posts are leaning inwards toward the 
> centre of the frame.

If they are leaning, but not curved, there may likely be NO barrel
distortion.

> Since I don't recall them being this way, I must assume this is
> distortion in the lens, although I don't recall exactly the name 
> for this effect.
> 
> Is this typical of the 35/2.8, and if so, are there Zuikos in 
> the 24-35 range which are better at controlling this effect?
> 
> I'm afraid the shot is ruined, as is a vertical of the same 
> church. At least with the vertical, I expected a problem, since 
> I don't have a shift lens. The horizontal shot came as a surprise 
> to me.

Verticals usually just give the subject more room to show the 
leaning, or temp the photographer in tilting the camera even
more.

Home science experiment:  Cut a perfect rectangle in a piece
of card stock.  Maintaining the same relationship between
the eye and the frame you've made, do some tilting at tall
objects and really examine the frame edges.  This isn't
a perfect representation of the optics involved, but is 
close enough to get the point across.

Larry 
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