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More on the Sigma 400 APO
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PostPosted: Tue Apr 10, 2007 8:35 pm    Post subject: More on the Sigma 400 APO Reply with quote

My continuing saga with Sigma 400 APO.
This is the third of these lenses I have had and all three had the same problems. Which is the inner element hazes over. I believe this is the APO doublet group and that it is actually hydroscopic. Well the haze has almost cleared on this model I have (PKA MF) this really confirms that the element group does absorb moisture. If not how can it dry out? Im also sure that any change of humidity will result in the elements reabsorbing moisture and another lengthy period for it to dry out again? It will never be perfect but it is better. The absorption process that most likely affects these old APO elements is know as Osmosis and used to be the killer for the gel coat on fibreglass boats. APO lens elements are a similar sort of plastic. Who would have thought my boating experience would apply to photography!

Well lets cut to the goods. This is more like how a Sigma 400 APO should perform when stopped down to f8 and the reason they usually fetch good money on eBay. When clear they will better the newer Sigma APO 400 zoom, in fact I dont think there is any easy to find at reasonable cost 400mm that can come near them. Which is why I keep trying to sort one out!
To larger file

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Long distant bird photo!

My advice buy a hazy one in the winter for little money and keep it as a Summer only lens. Dont expect to ever get one that will stay clear. Later models should be better but doubtful you would find one for under ?200 and I have heard of new Sigma APO lens hazing over and taking weeks to sort out. My mate took one to a tropical hot house and it never recovered.

PostPosted: Tue Apr 10, 2007 8:39 pm    Post subject: Reply with quote

Thanks for sharing! This is not good news at all! I will keep away my self from this lens.

PostPosted: Tue Apr 10, 2007 11:04 pm    Post subject: Reply with quote

I have my Fujinon f4.5 400mm which is much better but it is also twice the size and weight of a Sigma f5.6 400mm. The good thing about the Sigma 400 is it can be put in your bag, the bad thing is finding a good one and keeping any moisture away from it. I cant think of a 400mm lens that can match the Sigma 400 APO for quality, size and price, IF it is clear. I have taken a lot of good photos with them and seem them better lenses costing 10 times as much, but there always comes a day when you see the results and think whats going on, then you look close and see the thing has hazed up because of a bit of damp or humidity