i have a tamron 17-50 2.8 non vc that i bought used last year , so no warranty . i read a bunch of reviews before buying it that said it was a decent lens and acceptably sharp wide open. i have been quite disappointed with it , so much that i almost never use it and if i do it has to be at f8 which pretty much makes the 2.8 useless. i thought about sending it in for service but the cost for service plus original purchase would make it more expensive than a new one. i did a bit of googling and saw a few people that pulled them apart to try and repair them. i figured i had nothing to loose cause i dont want to pay to have it serviced and its basically useless as it is.
to start i popped the back cover off which was pretty easy then i undid the three screws (red arrow) and pulled out the first lens group and found 3 brass shims under it. the other 3 screws(blue arrow) hold another lens group(or at least thats what i think it is, plastic thing with glass on each end)and it had 3 brass shims also. i put it all back together with no brass shims anywhere and wouldnt ya know it , i had made it MUCH worse .
i figured i would put just 1 ship set back in at a time and try it . holy crap what a difference !. it is sharper at 2.8 now than it was at any other aperture before and focus is now good at least 90% of the time vs maybe 50% before.
here are some pics of what the innards look like and the last one is a crop of my eye shot wide open. its not prime quality of course but what a difference from before.
im not a very good writer so i dont know if this makes any sense to you guys but i thought i would share anyways lol.
IMG_1856 by sedwards679, on Flickr
IMG_1854 by sedwards679, on Flickr
IMG_1855 by sedwards679, on Flickr
IMG_1842 by sedwards679, on Flickr
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