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Sigma 400mm APO 5.6
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PostPosted: Wed Aug 31, 2011 3:48 pm    Post subject: Sigma 400mm APO 5.6 Reply with quote

I have this sigma for about half year now. Bought from ebay for 190.

It is OK lens, but that haze on focus element really disturbs me.
I would really like to try cleaning.

http://www.pbase.com/pganzel/repair_of_sigma_400mm_f56_apo

Does anyone have any experiance with that lens, is it worth to take apart?


RB291398 by rok.breznik, on Flickr

333859_2001858282548_1126294101_31861463_1875613_o by rok.breznik, on Flickr
middle lens

Some samples

RB114255 by rok.breznik, on Flickr

RB114299 by rok.breznik, on Flickr

RB313572 by rok.breznik, on Flickr

White heron by rok.breznik, on Flickr

RB114171 by rok.breznik, on Flickr


PostPosted: Wed Aug 31, 2011 4:05 pm    Post subject: Reply with quote

Those shots make it look like it is a very good lens.

If the lens performs that well with the haze, is it worth cleaning?

I'd say no as it performs fine as it is, you might damage it dismantling unless you have the correct tools like a lens spanner of the correct size.


PostPosted: Wed Aug 31, 2011 4:52 pm    Post subject: Reply with quote

Yes, those photos are with haze. Confused
I think that will be sharper, if that 5 element is cleaned.

Thanks for reply!


PostPosted: Wed Aug 31, 2011 4:57 pm    Post subject: Reply with quote

I don't think it's cleanable.
Keep it like that as a soft focus lens.
Stay away from Sigma for they are prone to haze.


PostPosted: Wed Aug 31, 2011 4:59 pm    Post subject: Reply with quote

despite the "dirt" on glass it still produces nice images... take it to fotomehanika in Ljubljana, they should clean it... I've had a similar problem with my 180/2.8 but not to that extent, cleaned it with ISO alcohol easily Wink


PostPosted: Wed Aug 31, 2011 6:01 pm    Post subject: Reply with quote

I have taken three of these lenses apart. It is very hard and damage is easy. I now have two semi-working lenses and a bag of bits. One performs worse after cleaning and reassembly then it did before (but this may be because I switched the original canon FD mount to the Olympus OM mount from the "bits" lens and this required using the final element from the OM lens with all the other optics from the Fd lens). The other lens has some play in the focus mechanism but does perform well.

There are two causes of haze in this lens. Oil from some part of the mechanics can condense on the doublet in the middle of the focusing group. Why it condenses on this element alone I cannot say, but at least this can be cleaned. However, cementation failure of this doublet (which actually does not move when focusing) is very, very common. That cannot be fixed.

I bought my samples quite cheaply (one was a gift), so was happy to try and fix them. But after three attempts at getting a really good lens, I would avoid these Sigma's like the plague unless I could inspect them before purchase. If you can get a good example, though, I do recommend it as it is a very nice lens.

At the price you paid for yours, I would leave well alone. You cannot fix the problem completely and are likely to cause other damage.

Mark


PostPosted: Thu Sep 01, 2011 9:54 am    Post subject: Reply with quote

Mark, thanks for great answer!