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Old Dec 17, 2007, 3:40 AM   #1
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Hi guys, in my attempt to be back to pentax ( if only i manage to sell my 30d ), i was asking myself if tamron, tokina and sigma lenses have the same front/back focus problem, they often have on canon.

Lenses like the sigma 17-70 or the tamron 28-75 would be really great if they don't suffer from those problems. I hate to have to send back the lens to calibrate, expecially since i always buy online and can't just bring back the lens to the store.
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Old Dec 17, 2007, 5:44 PM   #2
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Hi Lando,

Unfortunately, there's just no way to tell. Sample variations show up in all mfgs, but I think that they are somehow less frequent on Pentax bodies. I don't do FF/BF tests on the lenses that I get -- I just use them, and if the IQ isn't up to what I expect from my prepurchase research, then I'll test it to try to determine the problem.

I have both the Tamron 28-75/2.8 XR Di and the Sigma 17-70 and both of them focus well on both my DS and K10. I've shied away from Sigma for some time because of QC issues and CS problems in the past, but this one's a good one. The Tamron had gotten pretty much universal rave reviews at the time I purchased it, but I've heard a few complaining about focusing issues with these in the past few months. I also have quite a few Tokinas, and they have been very good, but I recently bought a Tok 20-35/2.8 AT-X Pro AF that just won't focus correctly. I sent it back to Tokina to see if they could help, but they returned the lens, saying that it was within spec. I also have a very expensive Pentax zoom that I'm sending back for evaluation after the holidays because I just can't get close to the sharpness that others seem are getting from the same model.

The bottom line is that any lens could be a dog. I've got a pretty healthy collection, and the great majority work as expected. It's been said that Pentax AF might be slower, but it's more accurate than other systems. I don't know if that is generally true, but it seems that either Pentaxians aren't experiencing the same kind of problems, or we are less demanding of our gear (and I kinda doubt the second). Digital makes it easier to spot "defects" with the ability to blow each frame up to unreal proportions. The best that we can hope for is to get a reasonably good sample of any lens.

Good luck in choosing some glass to use. Take what you read in complaints from users worth a grain of salt, and trust testimonials only from those who you can reasonably determine are fair minded (look up some of their posting history in the various fora) -- there's a small bunch of very vocal people who can find defects in anything, delight in complaining, and do just about nothing but. Just do your research ahead of time, make sure that those that you buy from have fair return policies, and don't be afraid to use them if you find a problem.

Scott
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Old Dec 18, 2007, 3:47 AM   #3
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Thanks, the fact is that with Canon, that I have now ( hopefully today i'm selling the body ), there are a lot of problems of ff/bf, with third party lens and with original even.

I remember I had much better results with my kit lens on k100d, than with the 30d and the sigma 24-60, which is an EX lens.

I think Daniel said in past how on pentax ( maybe because they share camera specs with other manifacturers ) these kind of problems are much more rare.
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Old Dec 18, 2007, 7:32 AM   #4
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Canon always has issues with non-Canon lenses, heck, even with Canon lenses when it comes to FF/BF, especially on the 20/30/40D bodies! It is more of a Canon issue. I have not run into any that FF/BF on my K10D yet! Luckily, my 20D focused dead on with every lens as well, but I also got lucky!! My same lenses on friends cameras FF/BF, rofl.

Also, personally, Tamron, Tokina, and Sigma make some of my favorite lenses, lol.
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Old Dec 18, 2007, 12:18 PM   #5
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At this moment the 2 lenses that would be great on the k10d are not made for pentax, the Tamron 17-50 and the sigma 50-150. If I could have these 2, I would be a happy pentaxian.

I know we have the da* lenses, but those are much much cheaper.
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