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12-09-2009, 09:04 AM   #1
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So, I got a Tamron lens & it's not focusing right.

Well, I got a Tamron 28-75 f2.8 to be a present from my folks for christmas, better that I get it than ask them to track one down for a decent price.

I did some test shots last night but with just artificial light & only looking on the camera screen it looked ok. Today I had some time to do some test shots in daylight & it looks like it's VERY soft wide open. I have a downloaded front/back focusing test chart, I'll print it & do some more tests later to if it's that. I'll need to look up how to do it properly.

The lens gets good reviews, at least on APS-C where corner-softness is not a problem as it's a FF lens. But I was aware that there might be AF problems, although I'll admit I'm disappointed that it appears to be a bad copy, especially as my camera does not have micro AF adjustment.

Has anyone experienced this? What's my best course of action? What do you think are the chances of getting it fixed before christmas? Or should I try for a replacement? Spanish shops are not known for their high quality customer service so they'll more than likely fob me off to Tamron.

Any advice appreciated as I am an SLR newbie. Many thanks.

100% centre crops:

At F8:


At F2.8:


12-09-2009, 09:14 AM   #2
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That does not look good. I would test with a tripod with SR off just to be sure though. After that, I would return it to where it was bought if it is no good. It is likely easier to just exchange it that to deal with Tamron. Good luck and Happy Holidays.
12-09-2009, 09:24 AM   #3
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I'm not sure it's just my imagination or real, but occasionally, I get the impression that my tammy focuses correctly on the first try then in AFC mode focuses to the wrong spot.

I need to play more with it, the lens has produced some good results but also some soft out of focus results from time to time. I have also seen F2.8 look soft as you show.

Last edited by Lowell Goudge; 12-09-2009 at 09:41 AM.
12-09-2009, 09:37 AM   #4
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Another Tamron w/ a K200D. How many shots have you tried w/ f2.8?

12-09-2009, 12:33 PM   #5
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QuoteOriginally posted by Jonathan Mac Quote
Any advice appreciated as I am an SLR newbie. Many thanks.
What makes you sure that the crop in the f/2.8 picture is of the exact spot where the camera focused? DOF is very shallow at f/2.8. A tree is a *terrible* subject for a test, because you have no way of controlling which branch the camera will choose to focus on.
12-09-2009, 12:44 PM   #6
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QuoteOriginally posted by Marc Sabatella Quote
What makes you sure that the crop in the f/2.8 picture is of the exact spot where the camera focused? DOF is very shallow at f/2.8. A tree is a *terrible* subject for a test, because you have no way of controlling which branch the camera will choose to focus on.
I chose the centre AF point for all the shots to check the centre sharpness of the lens. Both shots were taken from quite far from the tree (from the window of my second floor flat to the park below) and at 75mm. Unfortunately there's nothing else it could have focused on as the tree is isolated, and none of the branches are in focus. Some closer test shots of the text on food packets show that it's less than sharp as well. The crops I attached show the focusing error clearly, but it's obvious even when viewing the whole photo downsized to fit the computer screen.

I realise that fast zooms will likely show some softness at max aperture, but this is too much.
12-09-2009, 12:53 PM   #7
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QuoteOriginally posted by Marc Sabatella Quote
What makes you sure that the crop in the f/2.8 picture is of the exact spot where the camera focused? DOF is very shallow at f/2.8. A tree is a *terrible* subject for a test, because you have no way of controlling which branch the camera will choose to focus on.
+1

I would suggest an isolated, and simple subject. DOF could be the real issue here.

This might be a good candidate for a brick wall or other heavily textured surface at a slight angle. At f/2.8 you can focus on the center of the wall and see where the DOF centers. When I first got my FA 50/1.4 I also had a freak-out moment, until I investigated and discovered just how thin the DOF is at f/1.4~2.8
12-09-2009, 01:28 PM   #8
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QuoteOriginally posted by Jonathan Mac Quote
I chose the centre AF point for all the shots to check the centre sharpness of the lens. Both shots were taken from quite far from the tree (from the window of my second floor flat to the park below) and at 75mm. Unfortunately there's nothing else it could have focused on as the tree is isolated, and none of the branches are in focus. Some closer test shots of the text on food packets show that it's less than sharp as well. The crops I attached show the focusing error clearly, but it's obvious even when viewing the whole photo downsized to fit the computer screen.
If that is true, then you're not seeing a focus problem at all, but an overall softness problem. Would be interesting to see the picture you cropped this from, though.

12-09-2009, 03:29 PM   #9
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I just got a Tamron 28-75 in the mail to day, coincidentally. Bought it used off Ebay. After reading your post before it arrived, I ran around my yard taking pictures at f2.8. Nothing nearly that soft. (100% crop below)
Attached Images
 
12-09-2009, 04:35 PM   #10
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QuoteOriginally posted by Marc Sabatella Quote
If that is true, then you're not seeing a focus problem at all, but an overall softness problem. Would be interesting to see the picture you cropped this from, though.
What about having him MF to eliminate the AF as the issue? Because it might be that the AF is juuuuust-a-bit out of calibration wide open. So if MF gives a nice crisp shot there it's gotta be AF. If it still won't provide a reasonable focus then....it's a bit borked up.

I suggest it because the shot at f8 looks fine.
12-09-2009, 06:00 PM   #11
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Definitely, do some MF shots, also testusing a focus chart, also test using a real world subject where there are objects at all possible focus distances (eg, shooting the ground in front of you out to the horizon) so you can find the sharpest partof the picture. The goal is to separate out focus issues from overal lens issues. The posted picutre does not look anything that could *possibly* be a focus problem - focus problems results in misses of millimeters at close range, maybe centimeters at that sort of differences. But the tree doesn't even look *close* to in focus. There is no possible lens focusissue that could cause anything remotely like that.
12-11-2009, 12:09 AM   #12
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D'oh....maybe the OP was given too much homework? Nice suggestions Marc...and yeah, those are some weird results for sure.

Hopefully the OP is just bizzy and can come back to see what the issue might be.
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