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03-07-2007, 03:45 AM   #31
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So RiceHigh, if I understand you correctly, you think I might encounter BF/FF problems with the DA21 on the K10D, even if the lens seems to work correctly on K100D?

03-07-2007, 04:02 AM   #32
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As I said earlier my DA21 had slight BF (photographing test charts more than in real world shots) on the K100d but on my K10d it is very close to perfect..

Sorry to offer a different (first hand) experience... ;-)
03-07-2007, 04:15 AM   #33
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Depends

QuoteOriginally posted by tcom Quote
So RiceHigh, if I understand you correctly, you think I might encounter BF/FF problems with the DA21 on the K10D, even if the lens seems to work correctly on K100D?
I really think it depends on the specific lens and body. There may have been a QC issue. I can't be sure but some people have had excellent results with the 21 and others have voiced similar concerns that I have had.
03-07-2007, 04:57 AM   #34
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Ok, I will have to test the DA21 extensively on the K10D, once I find some time for it.

03-07-2007, 12:32 PM   #35
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does BF/FF have any effect with MF?

also as mentioned by previous poster, a firmware fix that remembers every Pantax lens recalibration automatically would be colossal if they did not leave this to a new camera upgrade as the K10D is so new.

Last edited by Akcelik; 03-07-2007 at 12:39 PM.
03-07-2007, 01:53 PM   #36
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QuoteOriginally posted by Akcelik Quote
does BF/FF have any effect with MF?
No it does not..
03-08-2007, 03:28 AM   #37
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QuoteOriginally posted by tcom Quote
I just reviewed my DA21 photos to check for any FF/BF problem.

f/8.0


f/8.0


f/6.7


Did I get a good copy, would the problem not be visible in these shots anyway, or should I have my eyes checked?
Hi Dominique

At the apertures you've used and the subject matter, I would not expect you to see anything. If you use a chart, or similar, that shows critical focus, and shot wide open, you may find that the precise focus point is just behind the point you used to focus on, even so, the balance between the near and far limits of acceptable sharpness would mean that the subject would still be sharp, just that more background than foreground would be in focus.

I actually believe that Ben has a defective sample, as it was OOF even at f9.0!

As far as it being specific to the K10D, I don't believe this to be an issue unless the body is consistently out of adjustment on the majority of lenses. I checked the two DA 21 samples I've had on both the istD, K100D and K10D and they were consistent, as indeed is my FA*24/f2.0 which has a very small degree of BF, which is only a minor issue at f2.0.

I have tested samples of the following lenses on the K10D and found them to be accurate (* also on istD and K100D, ** only on istD):

DA 10-17, DA 14*, DA 12-24*, DA 16-45*, DA 18-55**, DA 50-200*, D-FA 50 macro, D-FA 100 macro, DA 40*, DA 70*, FA 35*, FA 50 macro*, FA 28-105/f3.2-4.5*, FA 24-90/f3.5-4.5**, FA*300/f4.5*, FA 43 LTD**, FA 31 LTD**, Tamron 70-300 Di LD, Tamron 28-75 f2.8**, Tokina 20-35 AFII*, Tokina 24-200 AF**, Tokina 80-400 ATXII**. Sigma 180 EX macro**

The following lenses had BF, but were within the limits of acceptable sharpness (DOF) as defined by Online Depth of Field Calculator.

DA 21*, FA*24/f2.0*, FA 77 LTD*, Sigma 55-200 DC**

I don't have any issue with lenses that have a degree of BF if the DOF is within the limits of acceptable sharpness. I'd be more concerned if it front focussed (FF). In fact, some people feel that it is preferable to have a greater DOF behind, rather than in front, of the critical focus point. In some ways I tend to agree with this point of view.

The following lenses I found to have unnacceptable to severe FF & BF issues even after replacement or re-calibration and were returned or sold.

Sigma 10-20 EX**, Sigma 100-300 EX**, Sigma 18-50 DC**
03-08-2007, 11:06 AM   #38
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Thank you Richard

I am indeed not sure if BF/FF would be recognizable at these apertures. I also looked through the shots I did with the DA21 on the K10D, but as they were taken f/16, I would not see any problem anyway.

03-15-2007, 12:37 AM   #39
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21mm

QuoteOriginally posted by tcom Quote
Thank you Richard

I am indeed not sure if BF/FF would be recognizable at these apertures. I also looked through the shots I did with the DA21 on the K10D, but as they were taken f/16, I would not see any problem anyway.
When I get my new 21L today I will test it asap and get back to tell you how it worked out on the K10D bodies, of which I now have three. They assured me that the lens they are giving me was used to demonstrate it to potential customers at photo shows. I hope this one works out for me as I love this focal length.

Last edited by benjikan; 03-15-2007 at 03:50 AM.
03-15-2007, 06:02 AM   #40
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Ooooo.. a ringer lens.. hand tweaked to it's best specs.. ahhh the perks
(nothing really important to say, just wish there was a logical and forthcoming answer about the root cause of this error)
03-15-2007, 07:00 AM   #41
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I don't get it

I've never understood how front or back focus for just one particular lens can be a camera problem. The focusing sensor sits in the camera and meassures the contrast of the image. When the image is in focus, contrast is at its highest, and the camera stops focusing. Unless there is lag time from when the focus motor gets the "stop signal" and until it actually stops, and that lag time is lens dependent somehow?

Any theories on this, anyone?
03-15-2007, 07:09 AM   #42
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QuoteOriginally posted by Ole Quote
Any theories on this, anyone?
I could keep putting up a lot of reasons, but won't nail an answer. Looking at the machines in here as I walk by them during work, I wonder how these things can mess up creating a large car part. I get told it could be one of a hundred or a thousand reasons. There are a lot of variables with manufacturing that even the best engineers and computers can miss some details.
03-15-2007, 09:40 AM   #43
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Just did a couple of Tests

QuoteOriginally posted by jeffkrol Quote
Ooooo.. a ringer lens.. hand tweaked to it's best specs.. ahhh the perks
(nothing really important to say, just wish there was a logical and forthcoming answer about the root cause of this error)
The lens they gave me is the one given to one of the big photo magazines called "Reponses Photo" for testing for a major review. So far so good. tested it on the right side of a window frame and it seems pretty tight and shot a very funky wall across from my apartment. As the size of the image here won't suffice, I don't think it serves a purpose in posting it. But if you want to see it I can post it.

Aw...Here it is...

Last edited by benjikan; 04-05-2007 at 12:46 PM.
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