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[OM] Re: OM Teleconverter 1.4xA?

Subject: [OM] Re: OM Teleconverter 1.4xA?
From: Moose <olymoose@xxxxxxxxx>
Date: Sun, 18 Feb 2007 17:57:55 -0800
Darin wrote:
> Very good to hear. I'd love to see some samples, if you have the time, feel 
> free to send them directly to me if you'd like.
>   
OK, here it comes. Things aren't quite as good as I at first believed, 
but not a disaster, either.

My first test was a shot where the top corners are naturally dark, and 
it didn't look bad to me. It's not all that easy to find a relatively 
distant subject that doesn't move in the breeze around here, at least 
not without leaving the yard.  :-)  , so I gave up on pretty. 
Fortunately (yeah, right), they ended the utilities under grounding 
project around the corner, so I have a utility pole available.

I also took out my new right angle finder with 2x and remote cord for 
the 5D, so I could do my best to compare resolution of a few lenses and 
converters. So far, I've only addressed the Sigma 600/8 with Kiron 1.5x 
converter.

With the different subject, with detail in the center and plain blue sky 
in the corners, a vignetting worst case, vignetting is worse than I 
thought. Worse yet, the more linear subject revealed considerable barrel 
distortion. Fortunately, PTLens can deal with those pretty well. I 
simply tried a couple of distortion profiles for super wide lenses and 
found one that does a nice job on this image too.

Here's that image, as is at camera defaults, with correction for the low 
contrast of the lens combo, and with the PTLens corrections 
<http://www.moosemystic.net/Gallery/tech/Lenses/Sigma600/Pole.htm>.

I then went back to the original shot and applied the same corrections; 
quite a difference 
<http://www.moosemystic.net/Gallery/tech/Lenses/Sigma600/Juniper.htm>.

So, for some purposes, not an ideal combination, but for your goal of 
shooting critters and birds, where the outer parts generally get cropped 
anyway, it should work pretty well.

Moose

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