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[OM] Re: Lens questions

Subject: [OM] Re: Lens questions
From: Moose <olymoose@xxxxxxxxx>
Date: Sun, 08 Jul 2007 17:20:42 -0700
Nathan Wajsman wrote:
> Having reviewed the first couple of hundred images taken with the E410 
> and its 14-42mm kit lens, I have more or less concluded that I would 
> like a better standard zoom than the 14-42. Specifically, I am a bit 
> annoyed by the slowness of this lens, and by the quite visible barrel 
> distortion at the 14mm end.
>   
Nothing much to be done about the speed except higher isos or bigger, 
heavier (and more $) lenses which sort of defeats your light kit intent.

There is a pretty good, and very inexpensive, solution to the 
distortion, though. PTLens, $15, has parameters for all the common ZD 
lenses in its database and provides very easy correction. 
http://epaperpress.com/ptlens/index.html

BTW, the distortion is not simple barrel, but a more complex kind common 
in very short focal length lenses. It appears that, although 14mm on a 
4/3 camera has a FOV similar to 28mm on FF, it has distortion 
characteristics more like a super wide lens for FF than a 28mm.

Nice discussion of complex distortion here. 
http://epaperpress.com/ptlens/index.html

Unfortunately, you strip out the EXIF info from your posted images in 
this gallery, so one can't know which were taken at which focal lengths. 
I just took a few with what appeared to be WA views and/or have 
distortion and applied correction for the 14-42 @ 14 mm. It would appear 
that seeveral were indeed taken at or near 14 mm. 105, 206 & 275, though 
are mis/overcorrected, leading me to believe they were taken at longer 
focal lengths and 254 is just hard to tell. The rest seem to me to be 
very nicely corrected.
http://www.moosemystic.net/Gallery/Others/Wajsman/PTLens/

Given correct focal lengths, I'd expect the ones that are over done to 
come out right, too.
> I have looked on dpreview and Miranda for Olympus lens reviews but 
> cannot find any. 
For some tests of ZDs that address discuss linear distortion, 
http://www.photozone.de/8Reviews/index.html

Interestingly enough, you may get an idea of the distortion of most 
lenses using PTLens in reverse. Create a crossed lines pattern in any 
image editor, look at it in PTLens and see how the square pattern is 
distorted by different lenses and focal lengths. To compare different 
lenses, I apply the filter version of  PTLens in PS and save the 
alternative lenses as different layers, so I can switch between them.

Moose

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