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Crazy Sigma 400 APO
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PostPosted: Wed Apr 04, 2007 11:45 pm    Post subject: Crazy Sigma 400 APO Reply with quote

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 cant work out what is going on with the lens. Todays results were 100% better than the last ones. The hazy element doesnt 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?

PostPosted: Thu Apr 05, 2007 7:18 am    Post subject: Reply with quote

I had one like that, it worked reasonably wel. It had CA problems but under normal lighting the lens was ok.