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11-21-2010, 12:55 AM   #31
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AF happens with the lens wide open. So it doesn't matter whether you can see the DOF changes or not as you stop down. DOF is thinnest at 1.4 - if the AF system can focus there, that will work for 2.8 too. Of course, this doesn't take into account focus shift - that's the problem you've been exploring in this thread and one that AF systems don't seem to compensate for. That happens because AF determines focus at 1.4 and then stops down to 2.8, but at that aperture, the focusing is incorrect, so you'll get back focus or front focus. With the proper lens-camera interface, the lens manufacturer could encode the focus adjustment for a lens with focus shift, but it doesn't sound like this thing is done currently.

11-22-2010, 12:52 PM   #32
Rin
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Are the current variations of the Sigma 50mm 1,4 without issues or is front and back focus still very common.
11-22-2010, 02:47 PM   #33
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Check FW version. I have similar problem with my 35/2.8 Macro. But with last two version of firmware, the AF is more stable.

edit: I just saw that you use last FW. You can try set it again. Some time helps.
11-23-2010, 11:27 AM   #34
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tomorrow i will receive the same lens and a K5, i wonder how it will eprform i can return it within 2 weeks anyway

11-24-2010, 06:27 AM   #35
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I have an other issue with my Sigmalux I didn't mention before. In LR3.3 this lens is 'recognized' as a 70-200 mm F2.8 EX DG Macro HSM II zoom . So the Lens Profile corrections are done for the wrong lens AND as mounted on a Nikon camera, go figure, a Nikon ! That 'Nikon thing' is indeed a very strange turn of events !

Last edited by philippe; 11-24-2010 at 08:30 AM.
11-24-2010, 06:32 AM   #36
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I had some focusing issues with my sigma 100-300mm f/4 I adjusted it but it would still drift in and out from week to week. In the end I just gave up and reset it to +1 and strangely it seems to have settled down.

I'll also mention that my sigma 100-300mm f/4 is also recognised by light room as a sigma 70-200mm f/2.8 - which is very annoying when I want to do lens based image searches.

knock on wood.
11-24-2010, 10:48 PM   #37
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QuoteOriginally posted by Rin Quote
Are the current variations of the Sigma 50mm 1,4 without issues or is front and back focus still very common.
Sorry, I've been a bit busy. Well, the issue is definitely there. But not just with Sigma. I think it is "noticable" with lenses wider than F2.8. Congratulations. So, how's your K5 + Sigma turning out?

As for me, I would settle with that problem, coz there's no cure as of today. Like an online article pointed out, getting used to the lens' behavior, manually! I hate it, but I really really love the way a prime's picture's look. That "raw" brightness and sharpness.

For myself, I also discovered that 50mm was a bit short for my style of shooting. So I'm actually waiting for the Sigma 85mm F1.4 HSM. They seem to have solve this "focus plane shift" problem; of some online posts I read. They are on sale right now, but I just don't have the time to buy one and test... So, for me it's going to be this new year. Money's intact for it!
I'm also considering the FA 77mm F1.8. Seems more sharper, with screw-drive AF.

Last edited by icypepsi; 11-24-2010 at 11:03 PM.
11-24-2010, 10:50 PM   #38
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QuoteOriginally posted by SPA Quote
Check FW version. I have similar problem with my 35/2.8 Macro. But with last two version of firmware, the AF is more stable.

edit: I just saw that you use last FW. You can try set it again. Some time helps.
I think it will be far less "noticable" with lenses F2.8 and narrower. But I'd be very comfortable with a F2.8 lens, as my experience with the 3 lenses virtually disappeared with and after F2.8

11-24-2010, 10:54 PM   #39
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QuoteOriginally posted by Digitalis Quote
I had some focusing issues with my sigma 100-300mm f/4 I adjusted it but it would still drift in and out from week to week. In the end I just gave up and reset it to +1 and strangely it seems to have settled down.....
I don't know if you read my experience about the K7 not saving the microfocus adj. even when it says "Saved". I had the same problem, until I discovered it wasn't. Same thing, I used to feel it magically settles for some one value. But the weekly drifting... stranger still!! Maybe some more testing should tell what it is.
12-05-2010, 02:35 PM   #40
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I tried three copies of Sigma 50mm f1.4. All them have FF issue. The question is if Sigma management knows this issue?
12-05-2010, 02:52 PM   #41
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It'd be hard to convince me I wanted a Sigma 50 1.4 when just the Pentax-made 50's are such a candy store, anyway. Tried an FA 50? I just love em.

For 28-30ish fast-ness, that's still another matter. I considered looking for the Sigma 30mm, which seems fairly nice, though I went with the 28/1.8, instead, cause it has more useful-to-me qualities. (Despite a size that often makes me dream of FA 31s )

Three lenses are a lot to have the same issue: I presume you're sure it's not caused by something else? Sigma seems to be making nice stuff lately.
12-06-2010, 10:15 AM   #42
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The problem is FA 50 1.4 is not so good at wide open. But compared with my front focused Sigma 50mm, I would rather choose FA 50.

QuoteOriginally posted by Ratmagiclady Quote
It'd be hard to convince me I wanted a Sigma 50 1.4 when just the Pentax-made 50's are such a candy store, anyway. Tried an FA 50? I just love em.

For 28-30ish fast-ness, that's still another matter. I considered looking for the Sigma 30mm, which seems fairly nice, though I went with the 28/1.8, instead, cause it has more useful-to-me qualities. (Despite a size that often makes me dream of FA 31s )

No, I have other lenses. None of them has focus issue.

Three lenses are a lot to have the same issue: I presume you're sure it's not caused by something else? Sigma seems to be making nice stuff lately.
03-29-2011, 10:55 AM   #43
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I bought the Sigma 85mm F1.4

For those wondering what the hell this guy did eventually, I returned the Sigma 50mm F1.4 HSM and went on the vacation without it But after I got back, I waited and purchased the Sigma 85mm F1.4 a week ago and see similar problems, but much less pronounced and much more acceptable. Actually, I have another issue with the 85 in that I must be having a bad copy. I discussed it in this thread. Please take a look, you may have an answer!
03-30-2011, 01:02 AM   #44
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i've never had any luck with sigma's... in fact i wont bother trying them again... the DA 55 for me!
03-30-2011, 07:13 AM   #45
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QuoteOriginally posted by WerTicus Quote
i've never had any luck with sigma's... in fact i wont bother trying them again... the DA 55 for me!
I hope that's not the case with me. Coz, the previous time, this problem was shown by the DA 55 also. Besides, the DA 55, Sigma too has some fantastic optics. I would surely have gone for the FA 77, if it were SDM.
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