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Sigma SQ 300mm f/4 (M42)
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PostPosted: Tue Jul 30, 2013 7:28 am    Post subject: Reply with quote

There is a thing i've noticed as frequent problem with YS SIGMA models sponsoring soft-focus (macro) mode. Firstly grease gets into aperture system. People try to clean it but after that they are not able to reassemble lens correctly. Indeed SIGMA with additional front helicoid for soft-focusing (macro) are one of the toughest to put back together properly.

So the result of such tinkered reassembly is often improper adjustment of this front focusing system. Not reaching the deep end. This way the lens remains in soft-focus mode permanently. I've already fixed few examples of such problem. After correction lens delivers as intended. Still a bit low contrast of pastel colors true but good detail.

PostPosted: Tue Jul 30, 2013 12:51 pm    Post subject: Reply with quote

Honesty Calvin, I'd get rid of that lens, it looks awful. I was using my Tair-3C yesterday and it has no CA even wide open and is razor sharp, if you need a 300mm, grab a Tair, they are so cheap considering how good they are.

I agree with what Peter, Graham and Attila said, old Sigmas are often among the worst and the APO designation they use is a joke, the lenses aren't apochromatically corrected and honestly, I think in relation to old Sigmas, it just means the CA is a bit less than the outrageous level of their non-APO models.

PostPosted: Tue Jul 30, 2013 1:32 pm    Post subject: Reply with quote

I had one of these Sigma lenses with the double helicoid about 25 years ago, I think it was a 135mm lens. It was hateful. I bought it at a shop that was about 200 miles from where I live for about 70, which was a lot of money, but still not worth taking the damn thing back. I gave it away in the end.

PostPosted: Tue Jul 30, 2013 2:28 pm    Post subject: Reply with quote

That sounds familiar. I had the later Sigma 2.8/135 labelled as a Pentacon Prakticar. First time I tried it I put it on a tripod and shot it at infinity, f8. Couldn't find anything in the frame remotely sharp so it went in the bin. That was mint, like new too.

Some crops from my Tair-3C from last night, unsharpened, f8, to compare. My Tair looks like it fought a war or two, but still shoots perfectly.

I know CA is correctable, but I'd definitely pick a lens that wasn't riddled with CA to begin with.

PostPosted: Tue Jul 30, 2013 3:23 pm    Post subject: Reply with quote

I have the 4/200mm version of this lens but haven't had a chance to try it out yet.

PostPosted: Tue Jul 30, 2013 3:45 pm    Post subject: Reply with quote

It looks nice Ed, fingers crossed it's a decent performer.