Back Focussing?

EspressoJunkie

EspressoJunkie

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I've recently bough my second Tamron 28-75 (second hand from FFordes). I had one from eBay but returned it due to it back-focussing.

I'd hoped that the first was just a bad copy, but this one I've just got seems to have the same issue, all be it to a lesser extent. I know I can micro adjust, but even when trying various levels of adjustment the focus is still very hit and miss. Sometimes it nails it,and then other times it's way off. Like if I focus on the right eye and the person's head is at a slight angle, often the left eye ends up sharp, with the other eye clearly out of focus.

I am tending to use 2.8, and I realise this is a difficult aperture but I can focus with my 50mm at 2.8 every time!

I've tried using a test chart but it didnt really help, and I have a Focus Pyramid on it's way, which I'm sure will prove useful, but will probably arrive after the return period on the lens is up (10 days from last Fri).

I really do love the image quality that the lens gives, but is there any sure fire way to successfully calibrate it myself using micro adjustment? I can return it within the next week, but I'd really rather not if I can sort it myself.

I'd really appreciate input because I'm pretty clueless about it!
 
I'm a Canon user but I think the following still applies....

To calibrate the lens focus on a on object about 4 metres away whilst at the 75mm end of the zoom. Use live view magnified to check focus and then see if you can improve sharpness by twisting the manual focus in one direction or the other.

Change the micro-adjust in the relevant direction and then repeat until you can't improve the focus by manual focussing.

If after doing this you can't get repeatable accurate focussing results at all focal lengths give up and return the lens.

Unfortunately, if the same is true for Nikon as Canon, the body manufacturers won't give the focussing algorithyms to third parties so they have to reverse engineer them - this can create focussing inaccuracies.

Phil
 
When I was looking for a 28-75 I tried several in the shop before finding one I was happy with. The others were close ... but not close enough. After a bit of a knock I was having a focus issue with the lens not so long ago and couldn't fine tune it to get consistent results. In the end I sent it to Tamron's service agent - Intro2020 - and they sorted it out for me. Turned out that one of the internal elements had come loose and wasn't always (ever?) setting itself correctly.

Total cost was less than £50 including courier delivery and they had it back to me in under a week. Might be worth a thought.
 
Bristolian said:
When I was looking for a 28-75 I tried several in the shop before finding one I was happy with. The others were close ... but not close enough. After a bit of a knock I was having a focus issue with the lens not so long ago and couldn't fine tune it to get consistent results. In the end I sent it to Tamron's service agent - Intro2020 - and they sorted it out for me. Turned out that one of the internal elements had come loose and wasn't always (ever?) setting itself correctly.

Total cost was less than £50 including courier delivery and they had it back to me in under a week. Might be worth a thought.
Click to expand...

That's pretty interesting to know that there is such a variance in copies. When you tried other copies in the shop was is sharpness or focus that they didn't satisfy on ?

Part of me thinks I should just return it and try to find an old Nikon 35-70 instead.
 
They are a cracking lens, the image quality is great. I think ive just been unlucky!

My advice would be to check the focus thoroughly, and if you do find a problem then return it. My copy certainly would be unusable on a camera without micro adjust. MPB will have to take it back if you're not happy.
 
It should arrive today (if my neighbour can take it in) so I'll give it a good going over. Thing is even if it is out and I can get it calibrated for less than £50 it might be worth thinking about :thinking:

Only trouble with that is if I sent it off and it was still out I'd be £50 down and probably out of return date :lol:, maybe not such a good idea after all :)
 
Return it and try another one, micro adjust doesn't work well on zooms anyway.
 
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