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11-24-2014, 11:49 AM   #1
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Tamron 28-75: Another Lens Repair Journey

I bought a used Tamron 28-75 f/2.8 from a forum member earlier this year. The sample photos he sent me appeared to be fairly sharp at f/3.2 but my own experience has shown poor IQ at all focal lengths even at f/11. I've gone back and forth about sending it in to Tamron for a non-warranty repair since I'm not sure if I'm being too picky about the IQ, but I finally worked up the nerve to do it. So I plan to document my own repair journey in case anyone else finds themselves in a similar situation.

First I verified that the lens has a valid US serial number. Check (although I probably should have done this before agreeing to buy the lens).

Next I made a DIY GhettoCAL to check for FF/BF at close distance. I then realized the bigger issue is the ghosting that occurs between high contrast areas at greater focusing distances. Here are some sample shots I plan to send in to Tamron, taken from a distance of 20 feet using a tripod and 2-sec self-timer, with no filter.

75mm @ 2.8


100% crop


28mm @ 2.8
[

100% crop (note the fuzzy masonry)


I don't really want to send my camera in with the lens since the holidays are coming up, and Tamron claims it's not necessary. Any thoughts or advice before I send this lens in for service?

11-24-2014, 12:39 PM   #2
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Hi,
The first thing to ascertain is whether the lens is well centered at F2.8 @○ all FLs using distant views of trees etc to check whether the lens has equal sharpness left and right/top and bottom. The test you show here is taken outside in full sunlight onto a white/black test card, this is a very demanding test of contrast of which many lenses would struggle, lens testing sites would be shooting indoors at resolution charts. The Tamron 24-75 2.8 is a very good lens but I would expect a certain amount of fringing/veilling fully open, try the test in cloudier conditions., stopping down should also reduce these problems considerably. Also run a series of tests to see if the AF is spot on, although it doesn't look far out here. So far I'm not seeing anything terrible!
11-24-2014, 04:40 PM   #3
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Have you done any AF test to see if its spot on (test chart at angle etc)? Looking at those test shot it looks like it might be front focussing a little bit - look at book and table. Worth doing a test focussing with Liveview and comparing results.
09-04-2015, 12:20 PM   #4
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I just came across this thread while searching for help on my 28-75mm that is acting up today. Did you send yours to Tamron? What'd they do, and how much did it cost?

09-07-2015, 03:24 PM   #5
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QuoteOriginally posted by Edgar_in_Indy Quote
I just came across this thread while searching for help on my 28-75mm that is acting up today. Did you send yours to Tamron? What'd they do, and how much did it cost?
While I don't have the 28-75, I have a 70-200 that I bought used off of craigslist, and while it was decently OK, it was decentered on the right lower corner of the frame - the joys of buying used.

Eventually, I got enough money put aside to have it sent to their NY repair shop - cost about $225, not including shipping, and they fixed it in about 3 days. Part of the service included an CLA as well.

So far so good, and the lens is sharp across the frame now.
09-07-2015, 05:50 PM   #6
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Thanks for the input. I figured it would be cost prohibitive to have it repaired, and your experience helps confirm that.
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