Tamron 17-50mm f2.8 Front focusing ? Part 2

[eva2000]

A continuation of the front focusing issue here.

I got my 2nd copy of Tamron SP AF17-50mm F/2.8 XR LD via advance replacement and it seems to noticeably better in Auto focusing tests than 1st copy.

Focus chart test below showed much improvement, but real world shooting still shows front focusing with less severity and less frequency when it does occur compared to 1st Tamron. Still 2nd copy of Tamron isn't as sharp as Sigma 18-50mm EX DC Macro F/2.8 when at f/2.8 to f/4.0.

Quick summary of Auto focus performance on 3 lens from real world hand held photos:

1. 1st Tamron SP AF17-50mm F/2.8 XR LD (006687 Made in Japan) = 19 photos out of 20 shots would be severely front focused and be off by a loooong shot from f/2.8 to f/4.0 and only start to show improvement at f/8.0
2. 2nd Tamron SP AF17-50mm F/2.8 XR LD (006695 Made in Japan) = 4-5 photos out of 20 shots would be front focused slightly while another 4-5 photos out of 20 shots would show more noticeable front focusing at f/2.8. Most of front focusing clears up by f/4.0
3. Sigma 18-50mm EX DC Macro F/2.8 (Made in Japan) = Out of 20 shots, everyone would be near spot on where I'm focusing at f/2.8 and up. Same can be said for my Pentax SMCP-FA 50mm F/1.4, Sigma 105mm EX DG F/2.8 Macro and the Tamron AF70-300mm F/4-5.6 Di LD Macro 1:2 (Assembled in China) at their respective max-min aperture ranges.

Body used: Pentax K200D

[eva2000]

New Tamron SP AF17-50mm F/2.8 XR LD

@50mm at f2.8 AF - ISO 160 - AF Point Centered



@50mm at f4.0 AF - ISO 160 - AF Point Centered



@50mm at f8.0 AF - ISO 160 - AF Point Centered



Shame K200D doesn't have AF adjustments - Photome's EXIF info lists a field for AF adjustments though, so does that mean K200D could possible get this feature via future firmware update ?

[Marc Sabatella]

There are definitely those who hold out the hope that a firmware update will add an AF adjustment feature. But given you lens looks spot on from those test shots (although it still bothers me that I can't tell if you are shooting these correctly or not - the posted images are consistently show only on side of the test chart), I wouldn't be in an hurry to "correct" what seems to be a perfectly functioning lens.

Instead, I'd want to see your "real world" shots that show a focus issue that *cannot* be simply explained as the camera choosing to focus on something other than what you wanted it to focus on.

[Stratario]

[QUOTE=eva2000;426254]New Tamron SP AF17-50mm F/2.8 XR LD

@50mm at f2.8 AF - ISO 160 - AF Point Centered



QUOTE]


eva2000,

I'm very happy for you that you finally got a lens that seems to be focusing perfectly. I've been doing the same type of testing with my copy of the lens. I was wondering if you could do me a favor. Could you please repeat the same test but set the lets to approximately 21mm. Set if at F2.8 and centered AF point as above. You may have to get a lot closer to get the roughly the same area on the paper. I need to know if at 21mm the focus stays as good as what you are showing above, or does it shift to the back. Thanks.

[dave sz]

didn't someone post that a 45 degree focus test was no to be trusted? Something along those lines?

[dazman]

I just took my camera + lenses into Pentax and let them make the required adjustments to the camera for each lens. A easier and better option to me, rather than doing it myself & make a mistake. Dropped off the kit yesterday and was called today saying everything is ready to be picked up...quick and covered by warranty!

Do the focus test on the internet work?? I don't know, but Pentax Australia didn't recommend using them.

[edl]

Originally Posted by dave sz

didn't someone post that a 45 degree focus test was no to be trusted? Something along those lines?

I read something like that recently too, however I noticed my Sigma 18-50 2.8 FF quite a bit on my K20D, while it focuses perfectly on my K10D. Did a -7 adjustment based on results from the focus chart and all is well. Real world photos are now as sharp as they should be.