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06-19-2008, 05:57 PM   #16
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QuoteOriginally posted by Lowell Goudge Quote

- depth of field is not linear with distance, focusing should be 1/3 in front and 2/3 behind the focus line

my advise is forget the stupid chart and take photos of real subjects, not targets.
Geez Lowell, I wish you had written this a week ago when I first became anal about this FF/BF issue. After rechecking a DOF calculator and rethinking the whole thing I'm heading out the door to take some real photos instead of wasting my time on some stupid chart. THANKS!!!!


06-19-2008, 06:05 PM   #17
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Well, bummer...

Here are some "real world" tests using the second copy of the lens I got from amazon.

Focal point - M in Macro
This one actually looks pretty decent.

Focal point - MM in community
Off by a bit, it's FFing again. Notice the left of the test is clear (paper was at a slight angle to me). MM's are blurry.

Focal point - first "M" in memory card

Again, look at the letters. The left side (slightly slanting to me) clear. Right side very near the M (and the M itself) is blurry (I realize the far right side is past the DOF, but near the focal point should be clear).

I also took some portraits and snapshots at F/2.8. They're almost unusable when I crop, OOF not cropped and all show front focusing symptoms.

I really want to like this lens, but I think I'm going to return it and just get my money back this time. I bought it to shoot at f/2.8 at least in focus, if not sharp, and it's not doing this

I think I'll try to spring for a Pentax lens, so that if that FFs, I can just send both lens and camera to Pentax for repair or calibration or something.

Edit -- I wrote Pentax support, maybe they can help me. I recall having front focus (though not this bad) with several of my lenses, so perhaps my camera is out of whack. I'm curious as to what they say when I say the only lens I own now is the Tamron. Will they refuse to calibrate 3rd party?

Last edited by cputeq; 06-19-2008 at 06:18 PM.
06-19-2008, 08:10 PM   #18
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ok, just got finished doing more tests, this time a bit better centered and inside and outside. interesting that outside, I seem to have less of a problem, though still significant. fyi - tripod used but this time I cropped the pics so they aren't so huge. I'm also throwing in a pic of the lens cap where I was focused on the lettering, but the focal point is a good 3/4 inch forward from a shooting distance of around a foot.

well I think I'm with cputeq... I'll probably be returning this lens, but not happily. I think it has great potential, but it's a bit too far off. My intent was to use this lens often indoors usually at or around 2.8, and if the focus is as off as it proven to be, I'm left with only using it manually to get more reliable results.

Exposure: 0.013 sec (1/80)
Aperture: f/2.8
Focal Length: 55 mm
ISO Speed: 100

Exposure: 0.002 sec (1/640)
Aperture: f/2.8
Focal Length: 75 mm
ISO Speed: 100
taken outside

Exposure: 0.002 sec (1/640)
Aperture: f/2.8
Focal Length: 38 mm
ISO Speed: 100
taken outside

Exposure: 0.002 sec (1/640)
Aperture: f/2.8
Focal Length: 28 mm
ISO Speed: 100
taken outside

Exposure: 0.002 sec (1/640)
Aperture: f/2.8
Focal Length: 55 mm
ISO Speed: 100
taken outside

Exposure: 0.02 sec (1/50)
Aperture: f/2.8
Focal Length: 75 mm
ISO Speed: 200
taken inside

06-19-2008, 09:40 PM   #19
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Before purchasing mine from Amazon in May, I called Tamron and discussed the lens with one of their customer service reps. When I asked about the focusing issues she told me that if I had a problem with this I could send it in under warranty and they would recalibrate the lens to fix the problem. I asked her if she was aware of this issue and she said she was. She also said that it could be easily adjusted. My copy doesn't seem to have this issue. Has anyone sent their lens back for adjustment and what was the outcome? I love mine and wouldn't part with it.

06-19-2008, 10:26 PM   #20
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For those of you with a number of lenses front-focusing, you might want to consider this theory: Your camera is front focusing.

On this page you'll find a program that allows you to adjust the K10D's focus through the USB cable, without having to install a different firmware. I have not used it, so use it at your own risk. The other option is sending the camera in to Pentax...and wait 6-8 weeks until it returns.

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