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Archive 2005 · Tamron 28-75 Focus Issues
  
 
Jkan2001
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p.1 #1 · p.1 #1 · Tamron 28-75 Focus Issues


I thought I had a pretty sharp copy of the Tamron 28-75 F2.8 I bought new from bphoto a few months ago. Took it out for a concert shoot tonight and it seems like most the pictures were soft or OOF @ F2.8. The focus boxes were lit up over the faces and shutter speeds were well high enough, just wondering if i'm missing something.

I came home and did some test shots center focused and it looked sharp even @ 100% crop. Is it possible that it's in focus using the center point and OOF using the others? Lastly, I had a bump with a golf cart in the crowd (outdoor festival) and it knocked the lens hood off.

Do you guys think the jolt might have screwed something up inside the lens? It seems to be fine in all the test pics and even some of the ones i took after that but half the pics are OOF in the focus boxes.

Here's a screenshot showing how the face is still soft with all the EXIF info.

Example 1

http://i3.photobucket.com/albums/y78/Jkan2001/Screen003.jpg

http://i3.photobucket.com/albums/y78/Jkan2001/Screen004.jpg

Example 2

http://i3.photobucket.com/albums/y78/Jkan2001/Screen005.jpg

http://i3.photobucket.com/albums/y78/Jkan2001/Screen006.jpg

Pardon the screenshots, I don't know how else to show the EXIF info and a 100% crop in PS CS



May 22, 2005 at 08:35 AM
phidong
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p.1 #2 · p.1 #2 · Tamron 28-75 Focus Issues


Was he moving at all?


May 22, 2005 at 08:57 AM
Locster
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p.1 #3 · p.1 #3 · Tamron 28-75 Focus Issues


Just save it as a JPEG (not save for web) and the exif data remains intact. Anyone who wants to view it can then look at the picture properties


May 22, 2005 at 08:59 AM
Jkan2001
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p.1 #4 · p.1 #4 · Tamron 28-75 Focus Issues


phidong wrote:
Was he moving at all?


He was moving slightly just side to side as he was singing, I figured 1/180th and 1/350th would have been enough to stop motion.

And Locster i'll keep that in mind next time, I also wanted to show where the AF points were registered. It's just strange because i take test pic after test pic at home and it seems almost tack sharp @ F2.8 now both 28 and 75mm.

Here's an example: Both 100% crops

F2.8 @ 28mm

http://i3.photobucket.com/albums/y78/Jkan2001/Screen008.jpg

F2.8 @ 75mm

http://i3.photobucket.com/albums/y78/Jkan2001/Screen009.jpg



May 22, 2005 at 09:14 AM
JasonAng
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p.1 #5 · p.1 #5 · Tamron 28-75 Focus Issues


I had a similar experience w/ this lens...seemed decent at home in the backyard but at weddings it would often focus on the background even though the focus points were lit on the foreground. Also if I had to people together side by side maybe a few inches back between them only one would be sharp and the other would be fuzzy. I talked to B and H but could not return it as I already sent in my rebate. I then spoke with Tamron and they said this is a known issue on a certain percentage of lenses. I just sent it back to be recalbriated...hope I have better luck

Edited by JasonAng on May 22, 2005 at 10:05 AM GMT



May 22, 2005 at 01:52 PM
RDKirk
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p.1 #6 · p.1 #6 · Tamron 28-75 Focus Issues


If you want to test the focusing aspect, first, do not use all points active. The fact is that all those points are not all perfectly on the focus plane.

Do some testing using just the center point without recomposing. Make sure both the subject and the camera are perfectly immobile.

As the camera focuses, be sure to look at the image yourself and make note of what it actually focuses on. If it doesn't focus on what you intended, re-aim slightly to see if a shift doesn't get it to focus on what you want--you're exploring AF technique with this exercise, and yes, there IS a technique to proper AF focusing.

The only time I use "all points active" is when shooting a moving subject in AI Servo focusing mode. Even that is not 100 percent foolproof, it just provides a much higher rate of success than manual follow-focusing under the same conditions.



May 22, 2005 at 02:49 PM
Jkan2001
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p.1 #7 · p.1 #7 · Tamron 28-75 Focus Issues


RDKirk wrote:
If you want to test the focusing aspect, first, do not use all points active. The fact is that all those points are not all perfectly on the focus plane.

Do some testing using just the center point without recomposing. Make sure both the subject and the camera are perfectly immobile.

As the camera focuses, be sure to look at the image yourself and make note of what it actually focuses on. If it doesn't focus on what you intended, re-aim slightly to see if a shift doesn't get it to focus on what you want--you're exploring AF technique with this exercise,
...Show more

I did some tests using only center focus and they seem to be very sharp even @ F2.8. I just can't figure out why it's not performing the same out in the field when I'm really shooting. If it keeps it up I guess i'll send it back in to Tamron. I don't think I locked/recomposed in those pictures but I may have and that might be an answer to the softness



May 22, 2005 at 06:53 PM
steve_t
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p.1 #8 · p.1 #8 · Tamron 28-75 Focus Issues


If you can make it perform well on a tripod with a stationary target then chances are the problem is with technique rather than the lens.


May 22, 2005 at 07:31 PM
Loetje
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p.1 #9 · p.1 #9 · Tamron 28-75 Focus Issues


I have a Tamron 28-70 for a couple of month. He's verry sharp.
If you had for the incedent no problems with focusing and after the bump there where problems, I should bring back the lens for a check-out to Tamron. Maybe the lenses internal are damaged.



May 22, 2005 at 07:38 PM
Jkan2001
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p.1 #10 · p.1 #10 · Tamron 28-75 Focus Issues


steve_t wrote:
If you can make it perform well on a tripod with a stationary target then chances are the problem is with technique rather than the lens.


Well I don't have a tripod, however taking some steady hand held shots I consistently get sharp images so i don't know what technique could be wrong. I didn't focus/recompose and my shutter speed was well high enough to avoid camera shake and even to stop movement yet i still get soft/blurry images.



May 22, 2005 at 08:44 PM
 

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nutek
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p.1 #11 · p.1 #11 · Tamron 28-75 Focus Issues


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.

I have encountered a couple of lenses previously that exhibited this behavior before. Of course, I may be sprouting nonsense, and this post may prompt countless numbers to start testing their lenses for this phenomenon of far-sightedness as well. The focus madness never stops



May 22, 2005 at 09:10 PM
Jkan2001
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p.1 #12 · p.1 #12 · 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.

I have encountered a couple of lenses previously that exhibited this behavior before. Of course, I may be sprouting nonsense, and this post may prompt countless numbers to start testing their lenses for this phenomenon of far-sightedness as well. The focus madness never stops


Heh, I might look into this. If the lens keeps it up for another shoot then it's going back to Tamron. I don't know what else it could even be at this point, it's just odd that I did get a few keepers that were sharp like i'm used to but more than half are soft.



May 22, 2005 at 09:37 PM
hoagie
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p.1 #13 · p.1 #13 · Tamron 28-75 Focus Issues


Were these really taken at ISO 1600? That hurts image quality.


May 22, 2005 at 11:37 PM
RDKirk
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p.1 #14 · p.1 #14 · Tamron 28-75 Focus Issues


By the way, off topic, but notice how well evaluative metering did.


May 23, 2005 at 12:36 AM
Jkan2001
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p.1 #15 · p.1 #15 · Tamron 28-75 Focus Issues


RDKirk wrote:
By the way, off topic, but notice how well evaluative metering did.


What would you suggest for a lighting scenario like this, partial?

And Hoagie, I had to shoot 1600 since the fastest lenses I had that were F2.8 except a 85 F1.8 which I had in my bag and would've been too long.

It was at night by the time he went on (1030PM) and the stage lighting wasn't all that terrific, if i shot 800 ISO my shutter speeds would've been too slow. Besides ISO 1600 doesn't hurt image quality in any other department except noise. I frequently shoot @ 1600 and don't have any problems. Here's an example, absolutely no post processing or noise cleanup just resized.

http://i3.photobucket.com/albums/y78/Jkan2001/firsttolast2_RJLarge.jpg

I still haven't found an answer to the blurryness even with a very fast shutter, i guess the search goes on.



May 23, 2005 at 03:57 AM
chlee
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p.1 #16 · p.1 #16 · Tamron 28-75 Focus Issues


Hi,

noticed that you were using All active Af points which will average out the focus among those selected.... this might be the reason for the blurryness??

Edited by chlee on May 23, 2005 at 10:17 PM GMT



May 23, 2005 at 01:48 PM
RDKirk
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p.1 #17 · p.1 #17 · Tamron 28-75 Focus Issues


I said "how well," not "how poorly."


May 23, 2005 at 02:01 PM
kmbj
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p.1 #18 · p.1 #18 · 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.


Hi,

I just bought a Tamron 28-75mm a few days ago, and it does seem to have this exact problem. Focusing near (say, 1-3 meters) seems to produce sharp images, but if I focus it to a subject relatively far away (50 meters, for instance), I get rather blurry images - no part of the image seems to be clearly in focus. I was using a tripod for these shots.

I did some comparisons between my copy of the lens and a Canon 75-300 mm IS, both @ f/4.0, 75mm, and the shots taken with the Canon seem a tad sharper when focusing to a subject far away. Correct me if I'm wrong, but a good Tamron 28-75 should clearly outperform the Canon zoom. And f/2.8 makes things clearly worse with my copy of the Tamron.



May 23, 2005 at 02:18 PM
Jkan2001
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p.1 #19 · p.1 #19 · Tamron 28-75 Focus Issues


kmbj wrote:
Hi,

I just bought a Tamron 28-75mm a few days ago, and it does seem to have this exact problem. Focusing near (say, 1-3 meters) seems to produce sharp images, but if I focus it to a subject relatively far away (50 meters, for instance), I get rather blurry images - no part of the image seems to be clearly in focus. I was using a tripod for these shots.

I did some comparisons between my copy of the lens and a Canon 75-300 mm IS, both @ f/4.0, 75mm, and the shots taken with the Canon seem a tad sharper when
...Show more

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.




May 23, 2005 at 02:36 PM
Jkan2001
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p.1 #20 · p.1 #20 · Tamron 28-75 Focus Issues


RDKirk wrote:
I said "how well," not "how poorly."


I thought you were being sarcastic that's why I asked if partial might be a better solution in that kind of lighting. I usually just leave my camera on evaluative unless i'm shooting something like sillouhettes.



May 23, 2005 at 02:36 PM
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