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07-27-2011, 08:22 AM   #1
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In store testing of new lens

I've decided to replace my kit lens with a faster, wider, 2.8 zoom. I'm leaning towards the Pentax 16-50, over the Sigma 17-50 but the Tamron 17-50 is also still (just) in the running.

I want to avoid any FF/BF issues so I'm going in to the store to try out the actual lenses before I buy rather than buying online.

I'm thinking shooting a test subject wide open at both the long and wide end, centre focus will eliminate any obvious FF/BF lenses quickly but any tips and advice on how to test in the store to find the best copy would be greatly appreciated.

I've got a K10d so individual focus adjustments aren't possible and I don't want to do a "global" adjustment because I don't have any FF/BF issues on any of my other lens.

07-27-2011, 08:45 AM   #2
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Of the issues I've read about the DA*16-50, FF/BF is not one of them. Not saying it can't happen or hasn't, I've just never read of any such problems. The Tamron on the other hand, seems to be notorious for it. Remember that your K10d firmware has to be at 1.30 in order to use SDM. Otherwise, at 1.20 and lower, it will use the screw drive focus (which many would consider to be a good thing).

07-27-2011, 09:09 AM   #3
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You can print and take with you a focus test chart. Or do it the sloppy way and take a tripod and a meter and shoot at it at aprox 45...then you can check for FF/BF on the lcd screen.
Good luck...(and the tammy is great value for it's price).
07-27-2011, 09:36 AM   #4
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A lot of us are jealous that you have an actual store and lenses in it.

A lot of my lenses have problems that I have never noticed, simply because I don't use them that way. I handed my FA 35/2 to Marc Sabatella and he took like 3 shots that immediately showed lots of purple fringing. If I was thinking about buying that lens right there, I would be bothered by that fringing, but in my usage, I never see it. So my advice is to test where you might use the lens, if that's possible. For example, a lot of zooms with focus issues will behave differently at different focal lengths. If you intend to use them at the wide end, some back focus at 50mm is no big deal if you can be perfect in your daily usage range.

If you have read online reviews for each lens, see if you can observe personally any issues mentioned in the review. Sometimes these negatives look like giant problems in the review, and in person, they aren't important.

07-27-2011, 10:44 AM   #5
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I live very close to the largest pentax store on the west coast.
With that being said I know I'm lucky on that part.
Also Here In the Puget Sound there are 6or7 more shops that I know of, And I know theyre's more . ((((Im not taking about bestbuy frys or other junkstore stores. )))))
Everyone of the stores actually ask you if you would like to try out the lenses, cameras, filters, they even let you try them outdoors before you buy. All they want is happy customers.
Your specialty shop only carry the No1product after all you are the inspector.
The internet shops and bestbuys etc, usually carry a lot of the No2. Were do you think your rejects go. Also there motto is sell cheap sell alot you'll never see the customer and they dont know A No1 from No2 all there looking for is a bargain

Last edited by bobva; 07-27-2011 at 10:56 AM.
07-27-2011, 05:00 PM   #6
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Care to share the name of that store? I'm from a bit south of you but get to Seattle regularly. I have never actually seen a Pentax camera in a store so I would definitely stop in just to see it if nothing else.
07-27-2011, 05:57 PM   #7
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QuoteOriginally posted by Mike L Quote
I've got a K10d so individual focus adjustments aren't possible and I don't want to do a "global" adjustment because I don't have any FF/BF issues on any of my other lens.
I had a K-x at the time I ordered a 16-50 so had the same worry as you. First copy had huge BF so I returned it for another. Second copy had the same problem, maybe even worse BF. I gave up after that and returned it for a 12-24. All this was through Adorama who I bought from for their 30 day return policy.

There are problems with testing a lens in the store. First you need a very patient salesman. Next you have to deal with the store lights affecting BF/FF, really BF/FF should be checked under natural light. Next it is hard to tell on the LCD whether you have a problem, so you need to xfer the files to a computer to view. Next is, what about testing for decentering? That requires a different test and set up. More time and processing. This is why I like the 30 days (or 14 from B&H) to complete my testing. I first test the lens in "real life" situations; indoors, outdoors, close distance focusing and far. Then do the boring test shots for BF/FF & decentering.

So sure you could do a basic check in store, but more extensive testing could reveal a problem that becomes a warrant return if the store doesn't have a return policy.
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