Bad corner sharpness on tamron 17-50

Started Dec 8, 2012 | Discussions thread
jamesm007
Veteran MemberPosts: 5,471Gear list
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Re: Bad corner sharpness on tamron 17-50
In reply to Ian Leach, Dec 28, 2012

"Anyway you might want to try a second body in case K30 is the issue and/or give up on zooms and try to find a prime which meets your needs."

The below post was written by me March 4 2009. Almost four years ago.

"I had to exchange my new K20, for another last night. When I first got it I shot with my Sigma 17-70mm and did notice it was soft on the right at wide apertures. I knew the K20 could hold AF fine tuning for 20 lens so I thought that I would test for BF/FF and adjust it latter when I had time. Now I put on the kit lens, same thing. So I started just to play with AF tuning. Yesterday the K20 was really soft on the right even at f8 with my Sigma 10-20mm that pushed the button that says wait there's a problem; yesterday was the first time I really shot with that lens. I was discouraged and proceeded to try to tune the lens and body. Could not do it. All my lens where soft on the right, except the Pentax DA55-300mm (that lens never takes a bad pic it seems). Yet on my Samsung GX10 all my lens where 100% accurate, no softness, no OOF pics. And that brings up the second problem lots of OOF shots. Again I put it all off on I need to take some time and tune my K20D and lens. And to the fact it has higher resolution and will put a heavy MTF demand on lens. Not the case it was OOW (out of whack) big time.

Kinda amazing how the camera can make it seem like lens are bad. Lucky I had experience and another body (which I made the mistake of putting on eBay). If your a newbie and have only one or two lens, and buy another lens say the Sigma 17-70mm and see it soft on the right only, you will be led to believe its your lens that has a problem, in reality there is an almost equal chance of the body not working right with the lens. Its why I believe the mirror box system was wonderful and reliable for film, and for awhile with dSLRs at 10meg and under, but just can not be reliably and economically mass produced for sensors that will get even higher resolution, there is just too much demand in production. Add the cost of warranty service (even if under warranty you pay for it in the cost of the camera) with plenty of people sending in the bodies to get tuned correctly. If you where to poll all the dSLR forums and ask whats the top problem from a list that included AF, I would be willing to bet AF would be the top. And contrast detection mirror less systems eliminates that problem, as well as lowers cost substantial, and increases reliability. There would be no reason your camera would ever need calibration in its lifetime. I guess I am mad a little and ranting on AF... OK... but...

My replacement is fine, it does show any softness and its not producing OOF shots, so far so good with the few tests I have done. That's why I like buying local. Called Erik of Adrays of Dearborn MI, told him my problem and ask if they had another boxed K20D, they did. He said "done", before I even asked him to hold it for me until I could get there last night. Its only a 15 minute drive, and cost maybe $3.00 in gas. How much would it cost me to ship back with insurance? Probably much more. How long would I have to wait for my replacement? No contest, weeks versus hours. Or maybe I would have sent it to Pentax to get fixed. Wow just bought almost a grands worth of stuff from some place and now I have to wait weeks to use my stuff. Not if we have local BM stores that take care of you because they know that's how you will come back. Another rant I guess. Nothing will stop the internet from closing BM stores I know."

http://forums.dpreview.com/forums/post/31198293

Same thing happend before. I had a Samsung GX10 that went bad in one year or so. Samsung replaced it. Its when I finaly was able to take sharp pics with no OOF shots that were not my fault (look at my back posts late 2008). Also my Sigma lens now worked better yet. Sigma was right when I sent in my body and lens to them. They said its the body. But I said with 4 other lens working fine how could that be. Well there is absolute gold to be found at this lens and body rental place. How much better than to own such a company. Have your own lab and techs and test each and every product and take statistics and write what you find good/bad for the public?

Dig around and read all you can there is gold here at this web site -

http://www.lensrentals.com/blog/category/technical-discussion



Sometimes it can be the body out of wack a bit.

 jamesm007's gear list:jamesm007's gear list
Pentax K20D Pentax K-5 Sigma 10-20mm F4-5.6 EX DC HSM Pentax smc DA 55-300mm F4.0-5.8 ED Sigma 17-70mm F2.8-4 DC Macro OS HSM +9 more
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