Has my Tamron 17-50mm gone soft?

I have suspicions that my Tamron 17-50mm f/2.8 lens is softer than it should be, and in fact is asymmetrically so across either side of the image. I have a feeling that the left-hand side is generally softer at the 17mm end, whereas at 50mm the right hand side has a soft band going down it. I don't think this is a depth-of-field issue, since in some of my images objects towards the centre are very sharp over a range that includes blurred things to the right or left.

I did some testing with the following target:

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

if it makes you feel better, your f4 is similar to my 2.8... or not.. mine is slightly better.
i think you made the right decision.

I think you are right about there being a problem, probably decentering. If you mounted a different lens without moving the target or tripod and got equal sides you can rule out misalignment of the test. That leaves the lens.

Yah, btw that soft corner thing is usually more " normal " when shooting at 17 2.8 due to the field curvature at 17 mm " IF I AM RIGHT "... dont remenber this correctly, i think you can find the info on photozone.de

Just a small point to bring up.. Very few lenses are pin sharp from corner to corner and edge to edge.. Macro lenses are much better and flat field lenses are perfect..

Camera lenses are not designed to photograph documents,, this is where flat field lenses come into play..

Wide angle zooms like your Tamron 17-50mm F/2.8 will exhibit distortion and image decradation at either the wide end or long end or both especially at wider apertures.. Remember zooms are a compromise,,especially wide to tele zooms.. Using a newsprint for a test you have used your Tamron beyond its design brief,, they are not designed to shoot subjects like these..

Allow me to ask you this.. Were you happy with your Tamron before you did this test?? What is the image quality like in real life photographs??

Mine won't begin to impress until 5.6, once that's reached it's sharp everywhere.

yogestee wrote in post #5990748
Allow me to ask you this.. Were you happy with your Tamron before you did this test?? What is the image quality like in real life photographs??

Like I said, I'd been noticing things getting blurred along one side of a photo that were the same distance from me as clear objects on the other side, which is what alerted me to this in the first place. Let's take a "real-life" example, at 17mm taken at aperture f/5.0. At this length, the left-hand side is compromised. Take the scene:

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

HTTP response: NOT FOUND | MIME changed to 'image/png'

I see your point.. I stand corrected..

yogestee wrote in post #5992514
I see your point.. I stand corrected..

I know, it's a crying shame since the lens is so wonderfully sharp everywhere else.

Just curious.....did it always do this or was this something that developed.

In any case it needs to get fixed. Clearly it has a decentered or tilted element.

JeffreyG wrote in post #5992927
Just curious.....did it always do this or was this something that developed.

Hard to say. For the first three months I had it, I was trying to figure out whether it was front-focusing. I sent it in and that was corrected, it now focuses dead-on. I then started taking more pictures, and looking back over my library I can see this in quite a few photos.

Perhaps something has moved. The plastic hood mouting ring at the end of the lens moves a bit when pressed, but the front element isn't attached to that and seems secure. I don't know enough about optics to figure out what would cause the defect to move from one side to the other, but I don't think its the camera at fault. Anyway, I've packed it up with a CD containing the problem images. I'll send it off for repair tomorrow.

ettlz wrote in post #5992923
I know, it's a crying shame since the lens is so wonderfully sharp everywhere else.

ettlz,,it is a shame.. I own the Tamron 17-50mm F/2.8 and its big sister the Tamron 28-75mm F/2.8.. IMHO both are fabulous lenses,, crisp and sharp even at wide apertures..