Home · Register · Join Upload & Sell

Moderated by: Fred Miranda
Username  

  New fredmiranda.com Mobile Site
  New Feature: SMS Notification alert
  New Feature: Buy & Sell Watchlist
  

FM Forums | Canon Forum | Join Upload & Sell

1      
2
       3       end
  

Archive 2005 · Tamron 28-75 Focus Issues

  
 
kmbj
Offline

Upload & Sell: Off
p.2 #1 · p.2 #1 · Tamron 28-75 Focus Issues


Jkan2001 wrote:
Looks like we're in the same boat, did you get in contact with Tamron yet? If i still can't ifnd a solution that's probably going to be my next step.


I live in Finland and ordered the lens from Germany, so I'm not quite sure exactly where I should ship it, except back to Germany (I just received their instructions of how to proceed with the return). I'd much rather have Tamron re-calibrate the lens, since I'll probably just get a replacement from the German retailer, and I'd hate it if it had another quality issue. Or the German retailer might just conclude that there's nothing wrong with the lens (I'm slightly worried about how they'll check the flaw).



May 23, 2005 at 09:54 AM
Jkan2001
Offline
• • •
Upload & Sell: Off
p.2 #2 · p.2 #2 · Tamron 28-75 Focus Issues


kmbj wrote:
I live in Finland and ordered the lens from Germany, so I'm not quite sure exactly where I should ship it, except back to Germany (I just received their instructions of how to proceed with the return). I'd much rather have Tamron re-calibrate the lens, since I'll probably just get a replacement from the German retailer, and I'd hate it if it had another quality issue. Or the German retailer might just conclude that there's nothing wrong with the lens (I'm slightly worried about how they'll check the flaw).


I'd suggest send it to the nearest Tamron facility. I just took some more test shots and it seems like @ 100% crop they're slightly blurry/OOF but i'm not sure if it's normal and within acceptable limits. I found with about 20% USM increase they were tack sharp.

Here are some outdoor examples, I don't know how to post a 100% crop so I just went into PSCS and did a screenshot of a 100% crop. Both the text on the signs seem a little blurry, can any other Tamron owners comfirm if this is normal or needs to be calibrated?

http://i3.photobucket.com/albums/y78/Jkan2001/Screen002.jpg

http://i3.photobucket.com/albums/y78/Jkan2001/Screen001.jpg



May 23, 2005 at 07:07 PM
lafun1234
Offline

[X]
p.2 #3 · p.2 #3 · Tamron 28-75 Focus Issues


How do you rate Tamron service?
Is it fast response and how is return time?
Does problem be fixed as you specified without bring new problem?

Will think about this lens, but need konw service quality.

Thanks



May 23, 2005 at 07:13 PM
shooterkc
Offline

Upload & Sell: Off
p.2 #4 · p.2 #4 · Tamron 28-75 Focus Issues


I have the same lens. It's results are inconsistent to say the least. The best advice I can offer is to constantly be refocusing. I hit the focus button so many times to make sure it's in focus before I take a shot I'm amazed my camera's AF still works.

Chris

1Ds, 10D, Metz 54 MZ-3, 17-40L f/4, Tamron 28-75 f/2.8, 70-200L f/2.8



May 23, 2005 at 07:31 PM
Tim Wild
Offline
• • •
Upload & Sell: Off
p.2 #5 · p.2 #5 · Tamron 28-75 Focus Issues


Those photos of the Tamron box don't look at all sharp to me.

My Tamron 28-75 is very sharp, and the AF works perfectly both in tests and for weddings. You can see my focus tests here.

To work out whether the problem is the lens or the user, you need to do a focus test. IMHO the best focus test is the one I link to below. You need to be using a tripod, with single centre point AF, a cable release and preferably mirror lockup, to minimise changes of things disrupting the tests.

http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm

Only once you've done that can you objectively evaluate the lens. Despite all the well meaning posts most aren't very helpful, and they can't be without more information.

Edited by Tim Wild on May 24, 2005 at 04:17 PM GMT



May 23, 2005 at 08:07 PM
Jkan2001
Offline
• • •
Upload & Sell: Off
p.2 #6 · p.2 #6 · Tamron 28-75 Focus Issues


Tim Wild wrote:
Those photos of the Tamron box don't look at all sharp to me.

My Tamron 28-75 is very sharp, and the AF works perfectly both in tests and for weddings. You can see my focus tests here.

To work out whether the problem is the lens or the user, you need to do a focus test. IMHO the best focus test is the one I link to below. You need to be using a tripod, with single centre point AF, a cable release and preferably mirror lockup, to minimise changes of things disrupting the tests.

http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm

Only once you've done that can you
...Show more


Really? The Tamron box lookd decent, at least for my standards. I'm more worried about the last 2 pics I posted, the font on the signs seems a bit fuzzy. I guess a little USM in post processing wouldn't hurt but it's not great straight out of camera.

I'll try and make a test chart but at the moment I don't have a tripod or cable release.



May 23, 2005 at 09:17 PM
Tim Wild
Offline
• • •
Upload & Sell: Off
p.2 #7 · p.2 #7 · Tamron 28-75 Focus Issues


Without a tripod your results and conclusions can't be trusted - a tripod is an essential tool for a photographer.

Perhaps posting a 100% crop of the image would be more useful, with and without sharpening, but I wouldn't make any conclusions based on it given the lack of tripod.



May 23, 2005 at 09:29 PM
Jkan2001
Offline
• • •
Upload & Sell: Off
p.2 #8 · p.2 #8 · Tamron 28-75 Focus Issues


Tim Wild wrote:
Without a tripod your results and conclusions can't be trusted - a tripod is an essential tool for a photographer.

Perhaps posting a 100% crop of the image would be more useful, with and without sharpening, but I wouldn't make any conclusions based on it given the lack of tripod.


Yeah well, I don't shoot landscapes and haven't had the money to invest in a tripod yet. It's harder to shoot without glass than a tripod

I would appreciate it if you could tell me how to post a 100% crop though, my screenshot method isn't very good.



May 23, 2005 at 09:44 PM
Hrow
Offline
• • • • •
Upload & Sell: Off
p.2 #9 · p.2 #9 · Tamron 28-75 Focus Issues


I had a similar problem with the Tamron. Distant objects were often very soft. Close stuff was almost always very, very good as long as I was at 5.6 or better but on anything over 15' it was just whacky - sometimes the shot would be dead on and on others the focus was off - even on a tripod.

I complained here that the lens seemed to hunt for focus a lot - you could hear it - even after it should have been locked on and was greeted with a relatively hostile response from Tamron owners. What I suspect is happening is that you are exposing while the lens is trying to re or refine focus. Obviously, it is not moving very far but it may be enough to get you on the edge of your DOF.

I replaced it with a 24-70L and lo and behold, the focus hunting just disappeared. Many more keepers though when the Tamron was on I would be hard pressed to tell the difference except below 5.6.



May 23, 2005 at 09:44 PM
Jkan2001
Offline
• • •
Upload & Sell: Off
p.2 #10 · p.2 #10 · Tamron 28-75 Focus Issues


Hrow wrote:
I had a similar problem with the Tamron. Distant objects were often very soft. Close stuff was almost always very, very good as long as I was at 5.6 or better but on anything over 15' it was just whacky - sometimes the shot would be dead on and on others the focus was off - even on a tripod.

I complained here that the lens seemed to hunt for focus a lot - you could hear it - even after it should have been locked on and was greeted with a relatively hostile response from Tamron owners. What I
...Show more

That makes a lot of sense, I do notice it trying to refocus a few times during the shot and that slight movement might be screwing things up. Unfortunately I don't have the money to move ot a 24-70L or else i'd never pick up the Tamron anyways.

I guess i'll make sure the focus is dead on and locked before taking the picture next time and see if that helps. I did a little searching on an old thread and it seems like my copy is pretty much the same as everyone elses.



May 23, 2005 at 10:11 PM
kmbj
Offline

Upload & Sell: Off
p.2 #11 · p.2 #11 · Tamron 28-75 Focus Issues


Here's a 100% crop of a test image. No other part is any sharper than this, and I tried to make sure that the focus was as accurate as possible. A tripod was used.

Note the halation on the left side of the tree.

http://people.cc.jyu.fi/~bjorklid/tmp/example.jpg


Other Tamron users, how bad is this compared to your lens?



May 24, 2005 at 12:24 AM
Hrow
Offline
• • • • •
Upload & Sell: Off
p.2 #12 · p.2 #12 · Tamron 28-75 Focus Issues


I gave this some thought and went back and looked at some images. The problem images were all lower contrast. Given Canon's AF technology, low contrast images are more difficult to focus on by nature and I am beginning to think that this may be the source of the problem being described here and explain what I experienced with my copy.

When testing by shooting boxes and the like, the tendency is to 1.) Have a relatively high contrast subject (dark text against a light background) and/or 2.) manually focus. In both cases, the lens may be performing very differently then when confronted with a low contrast subject that is being AFed. This would explain why, in certain situations, my Tamron seemed to be hunting obessively. The image in the viewfinder never seemed OOF but I could sure hear the motor whining away.

One way to counteract this and/or test for validity would be to move the focus selection button from the shutter to the * button on the back of the camera via the Custom Function. Don't remember which one it is, but once you focus, it stays focused on that spot until you refocus. Might be worth a try to see what happens.



May 24, 2005 at 06:55 AM
J Rabin
Offline
• • •
Upload & Sell: Off
p.2 #13 · p.2 #13 · Tamron 28-75 Focus Issues


JKan. Three pages of posts and still blaming the lens. How about a different approach? Your concert pics were shot dark conditions ISO 1600 @ f/2.8. Did you check the Canon 10D manual for which focus points are hi-precision cross-hair points @ f/2.8? Any of them? I don't know the 10D specs, but on the 20D, only the center focus point has precision with an f/2.8 or faster lens in low light. That would explain your OOF portrait oriented shot too. This means, under these conditions, a user may be better setting the camera on center focus point only, relying on the most precise sensor, not trusting the peripheral ones. It also means this is one of the conditions to use FLR (focus-lock-recompose) with manual focus touch-up.
You are stressing a non-pro lens to its auto focus limites under these conditions.
Best of luck. J.



May 24, 2005 at 06:57 AM
RDKirk
Offline
• • • • •
Upload & Sell: Off
p.2 #14 · p.2 #14 · Tamron 28-75 Focus Issues


The lens doesn't determine the focus point. The camera does all that work and tells the lens how far and in what direction to focus. All the lens does is to make sure it follows the camera's command (and it does double-check itself, which you can often detect as a small correction after the main movement).

If the scene is very dark and the contrast of details is very low, the camera may rack the lens forward and back to find something to lock on. Sometimes it can speed past the detail--it often helps to manually put the focus close, then let the camera lock on.

Also, help the camera out by using some old split-image rangefinder tricks--look for linear contrasts to focus on. Back in the 70s when I was doing gobs of concerts (all cameras were freely allowed, and you could always get front-row seats and put your elbows on the stage if you were willing to get to the box office early enough), I usually focused on the mike or the mike stand with the split-image rangefinder in my F-1. That works as well with autofocusing.

In my exercises, I have not yet found any situation where there was enough light for me to see a straight line that the 20D with my Tamron 28-75 could not focus on. Where it has failed has been with very fine details, like the texture of a speaker grill--that I could see but was too fine in linearity for the camera to find.

If the lens is miscalibrated, that means it's not "speaking" the same increments as the camera--the camera says "move 3mm" and the lens moves 3.3mm instead; the camera says "move 5mm" and the lens moves 5.5mm instead. Another problem could be that it didn't correctly report its maximum aperture to the camera in the first place (the camera calculates the acceptable tolerance based on the maximum aperture reported by the lens).

Your last picture showed what could be optical problems instead of electro-mechanical problems. Run some tests in bright light with the camera on a tripod, using high shutter speeds and wider apertures (f2.8 down to f5.6) and focus manually to see how sharp you can get it. You want to distinguish between autofocusing problems (almost certainly calibratable) and optical problems (maybe repairable, maybe not).



May 24, 2005 at 07:17 AM
Jkan2001
Offline
• • •
Upload & Sell: Off
p.2 #15 · p.2 #15 · Tamron 28-75 Focus Issues


RDKirk wrote:
The lens doesn't determine the focus point. The camera does all that work and tells the lens how far and in what direction to focus. All the lens does is to make sure it follows the camera's command (and it does double-check itself, which you can often detect as a small correction after the main movement).

If the scene is very dark and the contrast of details is very low, the camera may rack the lens forward and back to find something to lock on. Sometimes it can speed past the detail--it often helps to manually put the focus close,
...Show more


I see what you mean, I haven't thought to try and manual focus as I thought it was almost certainly an AF problem. I tried to focus on high contrast targets, and it seemed to lock on quickly. However, it would sometimes try and recalibrate a few times. I doubt the lens is optically bad but it's worth a shot to check out.;

JRabin, I know it's the lens and not the camera because i've shot plenty of other concerts in way lower light then that pushing the limits @ F1.8 with a 50 and 85 F1.8 lens using various AF points as well as the center point and rarely having a blurry/OOF shot using the same technique.



May 24, 2005 at 09:51 AM
Jkan2001
Offline
• • •
Upload & Sell: Off
p.2 #16 · p.2 #16 · Tamron 28-75 Focus Issues


kmbj wrote:

Here's a 100% crop of a test image. No other part is any sharper than this, and I tried to make sure that the focus was as accurate as possible. A tripod was used.

Note the halation on the left side of the tree.

http://people.cc.jyu.fi/~bjorklid/tmp/example.jpg


Other Tamron users, how bad is this compared to your lens?


That looks considerably softer than mine, is that the center portion of the pic? Also how do you post a center crop?



May 24, 2005 at 10:00 AM
kmbj
Offline

Upload & Sell: Off
p.2 #17 · p.2 #17 · Tamron 28-75 Focus Issues


Jkan2001 wrote:
That looks considerably softer than mine, is that the center portion of the pic? Also how do you post a center crop?


Yes, it is the center portion of the pic. I focused on the tree or on that children's playground thingie, can't remember which for this picture. And no other part is considerably sharper, so this is not a focus-works-bad issue. Otherwise, some object nearer the lens or farther away would be sharper, yes?

That tree is some 40 meters (120 feet) away. If you haven't tried it yet, I'd suggest you take a picture of some subject as far away as that - you might get even softer images. Preferrably so that there are other subjects farther and nearer - this way you can see if it really is about the focusing not working well or if it is about this "far-sightedness" issue - if something else is better in focus, then it's a focus issue. If everything is at least as soft as the subject you focused on, then it is an optical problem. I'm not an expert on how to test whether a lens has a specific flaw, so correct me if that logic is flawed.

You get a center crop by cropping the center of the image ;). That is, just select a small part of the image in photoshop/GIMP/whatever, Ctrl-C, paste as new, save, upload to webserver and link here. That's what I did, anyhow.

Edited by kmbj on May 25, 2005 at 12:28 PM GMT



May 24, 2005 at 04:13 PM
Jkan2001
Offline
• • •
Upload & Sell: Off
p.2 #18 · p.2 #18 · Tamron 28-75 Focus Issues


kmbj wrote:
Yes, it is the center position of the pic. I focused on the tree or on that children's playground thingie, can't remember which for this picture. And no other part is considerably sharper, so this is not a focus-works-bad issue. Otherwise, some object nearer the lens or farther away would be sharper, yes?

That tree is some 40 meters (120 feet) away. If you haven't tried it yet, I'd suggest you take a picture of some subject as far away as that - you might get even softer images. Preferrably so that there are other subjects farther and nearer - this
...Show more

Here are my 100% crops of objects that were at least 100 feet away. Not spectacular but that range @ F2.8 isn't that bad I guess.

http://i3.photobucket.com/albums/y78/Jkan2001/truck_RJLarge.jpg

http://i3.photobucket.com/albums/y78/Jkan2001/tree_RJLarge.jpg

http://i3.photobucket.com/albums/y78/Jkan2001/table_RJLarge.jpg

http://i3.photobucket.com/albums/y78/Jkan2001/rail_RJLarge.jpg

http://i3.photobucket.com/albums/y78/Jkan2001/brick_RJLarge.jpg



May 24, 2005 at 05:37 PM
RDKirk
Offline
• • • • •
Upload & Sell: Off
p.2 #19 · p.2 #19 · Tamron 28-75 Focus Issues


nutek wrote:
your lens might be suffering from "far-sightedness" (don't laugh!). The focus calibration is ok for near subjects (i.e. most focus test charts, etc), but is out of whack for relatively far subjects.


That would be nearsightedness.



May 24, 2005 at 07:16 PM
saaketham
Offline
• • • • •
Upload & Sell: On
p.2 #20 · p.2 #20 · Tamron 28-75 Focus Issues


Jkan2001 wrote:
Here are my 100% crops of objects that were at least 100 feet away. Not spectacular but that range @ F2.8 isn't that bad I guess.


They all look horribly soft. Just like the Tamron 28-75 and Sigma 24-70 I recently bought on Buy & Sell. By f/4, images are much sharper and f/5.6, it's great. f/8 seems to be the sweet spot. Did you try shooting with higher ISO. I got sharper images at f/2.8 when shooting at ISO-400.



May 25, 2005 at 12:12 PM
1      
2
       3       end




FM Forums | Canon Forum | Join Upload & Sell

1      
2
       3       end
    
 

You are not logged in. Login or Register

Username       Or Reset password



This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.