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07-28-2013, 12:46 AM   #1
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Help me test a DA 12-24 for faults please

I bought a 12-24 off ebay as broken. The description said that it took photo's, but had come into the sellers possession listed as not working so was being sold for parts. As a result, I bought it at a ridiculously silly price, and when I say silly, I mean silly Im more than happy to get it repaired but want to know how to test it to find out what is wrong with it.
My suspicion is that the focussing isn't quite right, if I take 2 photo's, both with everything on Auto on my K30 then the pic using my DA 35 F2.4 is noticeably sharper than the 12-24. (Maybe because it is a prime?)
Can someone help me out here with a few basic tests to run to get to the bottom of this, it could be that it is just a case of calibrating the camera to the lens, or it could be that the that Im trying to take the wrong type of photo's (too close up), but some basic tests or a testing methodology would be good so I can eliminate possibilities - it could be there is nothing wrong, but I don't know enough to test with any confidence and don't want to send it off for repair without knowing what I want repaired.
Of course it could be seller error, and there is nothing wrong with it, and Im looking for faults that are not there, which is why I want to test it properly

I was going to sit in the garden and set some objects up on the garden table and take a photo at every aperture and see how the DoF changes and check for focus, then do the same for the DA35, but that is as far as I can think for testing? Im limited to the garden today as I have the kids...
This is the only zoom I own, so I can't compare like for like, I have to test it against either the 35mm or a 100m Macro..

Thanks

07-28-2013, 01:23 AM   #2
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I really don't see why trying to find what / if there's something wrong with it. Just use it as usual and you'll see if it's broken or not. Congrat for getting this lens for a low cost because it a very good wideangle zoom
07-28-2013, 01:29 AM   #3
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There is that, but Im off on my travels soon, so would hate to take it and find out something is wrong later and lose photo opportunities that I won't get again, which is why I wanted a robust testing method so that I have confidence that all is OK
07-28-2013, 03:03 AM - 1 Like   #4
Ole
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Focusing accuracy and focusing mechanism: Test at three focal lengths (12, 18, 24mm) at F5.6 on subjects somewhat close, some distance away, and infinity, all set to autofocus.

Exposure accuracy and aperture mechanism: Test all F-stops (4, 5.6, 8, 11, 16, 22) in Av mode at, say at 24mm and just one subject distance. Use a front lit subject. Don't be worried if you see sharpness and contrast drop at F16 and F22, that's expected due to diffraction. But all images should be exposed the same.

Use a tripod to eliminate camera shake as a factor.

Always use the lens hood if you have it.

Then examine all images. If you're happy with the quality then you're all set. No need to compare to a prime, you don't have primes anyway that matches the focal lengths of the 12-24.

07-28-2013, 03:34 AM   #5
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QuoteOriginally posted by Ole Quote
Focusing accuracy and focusing mechanism: Test at three focal lengths (12, 18, 24mm) at F5.6 on subjects somewhat close, some distance away, and infinity, all set to autofocus.

Exposure accuracy and aperture mechanism: Test all F-stops (4, 5.6, 8, 11, 16, 22) in Av mode at, say at 24mm and just one subject distance. Use a front lit subject. Don't be worried if you see sharpness and contrast drop at F16 and F22, that's expected due to diffraction. But all images should be exposed the same.

Use a tripod to eliminate camera shake as a factor.

Always use the lens hood if you have it.

Then examine all images. If you're happy with the quality then you're all set. No need to compare to a prime, you don't have primes anyway that matches the focal lengths of the 12-24.
Thank you - will have a go later and post back if any concerns arise..
07-28-2013, 04:42 AM - 2 Likes   #6
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Just make sure nothing is decentered (for example, if one side of the photo is blurry when it shouldnt be)
Feel free to look at sample photos posted for this lens, in the lens reviews section as well as in the sample photo search tool. Just remember that post-processed photos are sharpened up a lot, especially with UWA lenses. In lightroom, I tend to use 40, 0.7, 40 and greater for my 14mm prime.
07-28-2013, 11:44 PM   #7
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Might point out, that if you use live view, the focus will be completely accurate, because it focuses using the image on the sensor, not the AF sensor. So you can take a shot with live view (on tripod), then take the same shot with normal auto focus through the viewfinder. If they're the same, then the lens is adjusted correctly for the camera's auto focus.
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