Tamron 28-75 XR Di Owners Help! (attachment)

[charleshamilton]

I have a Tamron 28-75 that I just got and use on a 20D, and it seems to have a problem focusing. I have read that some people have gotten some soft 28-75s and was wondering if anyone that knows they have a sharp copy can look at the attachment and tell me if this is considered sharp. The actual photos I have shot with it don't seem very sharp. I just want to rule some things out. I shot this at 2.8 at 75mm about 2 ft away. It also seems to have a front focus problem.

Any help would be appreciated.


Thanks, Charles

[IainB]

Can you post any other photos you consider not to be sharp? It's not easy to make that judgement based on one shot.

[Persian-Rice]

A "sharp" copy is a rare with these, most are not very sharp wide-open, and a few are very sharp. This lens is generally not extremely sharp at 2.8 but sharp f/4 and smaller.

I would say 2/10 are very sharp, 6/10 are sharp at f/4+, and another 2/10 are just massively screwed up in some way or other. The only way to get an ultimate sharp one is to go return it 6-7 times and cross your fingers.

Use a tripod, focus on a number, lets say 5. I have never heard of a backfocus issue with the Tamron.

Seriously though, It looks like you have one of those "6/10" copies most people have. Very usable and very sharp at f/4+ most people don't bother to search for one of the super sharp copies as the normal Tamron is good enough. even at f/2.8 its not that soft.

[Olegis]

The AF system will always focus at the closest contrast object - you may point the camera at the "5" digit, but if the sensor will cover the marks that are closer to you than the "5" digit, the camera will focus on them - and you'll think that it has front-focussing issues. Try this test (http://www.photo.net/learn/focustest/) instead.

Now about sharpness at 2.8 - you'll have to post another image or two, it's hard to tell anything from this one. Also, don't expect this lens to be SHARP wide-open, all lenses tend to be softer at those wide apertures, especially these non Canon L zooms.

If your pictures are like this one (http://www.pbase.com/olegis/image/36114206/original) at f/2.8 - you can consider your lens sharp (this image is straight-from-the-camera-unedited-large-fine-JPEG file, shot at 75mm, f/2.8, ISO 800 with flash and my 10D). I think it's reasonably sharp, and it can be sharpened very well in post-processing.

[tim]

From that one shot things look ok to me. I assume you were focusing on the 5?

[charleshamilton]

Thanks for the link to the focus test. Here is a pic of the box at 2.8 and 4.0 Both at 75mm. I have done tests with a ruler at 75mm, 50mm, and 28mm singling out the Left, Center, and Right focal points running it through EOS Capture to check the focus point. From about 50mm on down I get a lot of front focusing.

Charles

[tim]

I still don't see any problems. Can you take a photo of a person, put it on a website somewhere, and post a link to it? There's lots of details in people that would help us give you better advice. Try F2.8 and something a little higher than F4 if you can manage it - F6ish or F8 maybe.

You might be interested in these tests (http://www.mrwild.co.nz/ExperimentalGallery/Tests/LensTests/index.html) I did a while back.

[Adam Hicks]

Persian-Rice continues his peculiar and relentless assault against this lens, but a sharp copy is certainly NOT 'rare' these days. That lens is doing exactly what it's supposed to in my opinion, and the box shots look excellent for being wide open and given that the 20D is slightly soft anyways without in camera sharpening and considering the light JPEG compression artifacts. Looks like your lens is a good one. If I shot that same image with my 100-400L at 100mm f4.5 it wouldn't be nearly as sharp - and the 100-400 is a fabled 'L' and was 4x the price.

Fantastic performance for a wide open lens (under $1200.)

Adam

[maderito]

The depth of field at f/2.8, 75mm, 2 feet is about 1/8 inch in front and behind the focal point (total 1/4 inch). With these tolerances, focusing errors can be related to technique rather than inherent lens or camera problems.

This is one of the few, affordable f/2.8 "walk around" lenses. Walk around and capture some shots. I think you'll be pleased.

[pcasciola]

I agree with Adam. The few people that got bad copies of this lens continue to try and rip it apart, yet 85+% of the people who get one love it. Mine is as sharp wide open as any f/2.8 lens in this zoom range I've ever seen, including the Canon 24-70L.

As for whether you got a bad copy here, it's really hard to tell from these posts. It looks like all these shots were taken in low light. Can you try some during the day with no flash, and post links to the pictures rather than attaching them, because the JPEG artifacts are very strong on the shots you embedded.