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Rob Leslie
Joined: 20 Mar 2007
Posts: 1103
Location: UK Swindon
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 Posted: Wed Apr 04, 2007 11:45 pm Post subject: Crazy Sigma 400 APO |
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Rob Leslie wrote:
Today I did some more test shots with the Sigma f5.6 400 PKA MF. The last results were disappointing due to haze on the middle element group. Today every shot from f7.1 was very good with a slight improvement at f8 and f9 Wide open and f6.3 were not bad but a little flare could be seen.
The point is I can’t work out what is going on with the lens. Todays results were 100% better than the last ones. The hazy element doesn’t seem to have changed but maybe it has? As I have mentioned before I think these old Sigma APO elements are ‘hydroscopic’ so maybe the humidity is affecting it ? I wondered if anybody had any idea?
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Pentax K10D & K100D. Many Tamron Adaptall SP lenses, Fujinon f4.5 400mm. A loved Lens Baby 2, Lubitel triplet +++ and many film cameras. Mainly a Digital user inc G5, GR2
http://robstreet.blogspot.com/
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http://roblesliephotography.blogspot.com/
http://www.flickr.com/photos/64956578@N00/ |
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Jigt
Joined: 16 Mar 2007
Posts: 412
Location: Belgium
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| Posted: Thu Apr 05, 2007 7:18 am Post subject: |
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Jigt wrote:
I had one like that, it worked reasonably wel. It had CA problems but under normal lighting the lens was ok.
Guido
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nature pictures at www.ranaphoto.net
My pictures in the http://www.pentaxphotogallery.com/guidofranssens |
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