21mm Limited Back Focus Confirmed

benjikan · 03-05-2007, 05:45 AM

Just got the response from Pentax via their head office in Germany. They confirmed that there is a back focussing problem with the 21mm Limited exclusively. They offered to set up one of my bodies to work in conjunction with the lens, which I refused. I do not wish to take up one body exclusively for that lens. I am waiting on a firmware fix or a chip set change for the lens. I will use it in manual focus only. They are sending me back the two bodies and the two lenses i.e. the 21 and the 16-45 which didn't have a problem and focussed perfectly on the "0" calibration point. I will wait for the 16-50 f2.8 which I should have in ten days to use in lieu of the 21mm Limited. If it is anything like the Canon 17-40L lens which I used on 80 percent of my magazine work, I will probably do the same with it.

Ben

amcinroy · 03-05-2007, 06:15 AM

Thanks for posting the info Ben,

I will keep my fingers crossed on a firmware fix rather than a chip fix.

In the meantime, I was out using this lens at f8 at the weekend and wow, it's sharp. I will certainly be keeping it.

Andy

Piotr · 03-05-2007, 06:21 AM

Andy,

beautiful shot

RiceHigh · 03-05-2007, 06:25 AM

But there was yet another DA 21 user who reported FF instead:-

RiceHigh's Pentax Blog: DA 21 Limited Front Focusing or Back Focusing?

Also, I cannot see how a firmware or chip upgrade can help to resolve the problem. I guess it is about the weaknesses of the Pentax AF system and/or the in-born optical errors, probably the spherical aberrations which cause the problem:-

RiceHigh's Pentax Blog: AF Accuracy's Dependency on Lenses and Yellow Light

Originally posted by benjikan

Just got the response from Pentax via their head office in Germany. They confirmed that there is a back focussing problem with the 21mm Limited exclusively. They offered to set up one of my bodies to work in conjunction with the lens, which I refused. I do not wish to take up one body exclusively for that lens. I am waiting on a firmware fix or a chip set change for the lens. I will use it in manual focus only. They are sending me back the two bodies and the two lenses i.e. the 21 and the 16-45 which didn't have a problem and focussed perfectly on the "0" calibration point. I will wait for the 16-50 f2.8 which I should have in ten days to use in lieu of the 21mm Limited. If it is anything like the Canon 17-40L lens which I used on 80 percent of my magazine work, I will probably do the same with it.

Ben

RiceHigh · 03-05-2007, 06:27 AM

Originally posted by Piotr

Andy,

beautiful shot

Yes, good mood, good composition and nice colors.

joele · 03-05-2007, 06:34 AM

As to the 21mm thats very interesting.. I had a lot of problems with the focus accuracy of the DA21 on my K100d but actually don't seem to have a problem with the K10d... weird.. will be interesting to see what Pentax do since they admitted the fault..

benjikan · 03-05-2007, 06:38 AM

Originally posted by amcinroy

Thanks for posting the info Ben,

I will keep my fingers crossed on a firmware fix rather than a chip fix.

In the meantime, I was out using this lens at f8 at the weekend and wow, it's sharp. I will certainly be keeping it.

Andy

Why You and Not Me? I guess 'cause you are shooting parallel to the subject...Nah, that is not the case as they tested mine and it was back focussing. I'm telling you it is my Karma for leaving Canon so abruptly. It is called the "CC" or the Canon Curse...

Alvin · 03-05-2007, 07:51 AM

Ben,

I'd be careful if you are considering going back to Canon after getting a Canon Curse. You may get a Pentax Curse, or does that exist? I don't want to jinx you.

Richard Day · 03-05-2007, 08:45 AM

Originally posted by benjikan

Just got the response from Pentax via their head office in Germany. They confirmed that there is a back focussing problem with the 21mm Limited exclusively. They offered to set up one of my bodies to work in conjunction with the lens, which I refused. I do not wish to take up one body exclusively for that lens. I am waiting on a firmware fix or a chip set change for the lens. I will use it in manual focus only. They are sending me back the two bodies and the two lenses i.e. the 21 and the 16-45 which didn't have a problem and focussed perfectly on the "0" calibration point. I will wait for the 16-50 f2.8 which I should have in ten days to use in lieu of the 21mm Limited. If it is anything like the Canon 17-40L lens which I used on 80 percent of my magazine work, I will probably do the same with it.

Ben

The DA 21 does seem to have a generic BF problem. I have tested 2 samples and they were identical. For most purposes it doesn't come into play as the DOF of the lens is quite large even at f3.2 and in many shots it will not be noticeable as the near limit of acceptable sharpness will be just within the focus point.

Here is a test at f3.2

At smaller apertures and with reasonably distant objects (as in the beach shot posted by Andy) it wouldn't show up, in fact it will give added depth of field behind the focus point which could be beneficial.

It will obviously be quite critical at close subject distances and at, or near, max aperture, which is how I suspect Ben is working with this lens.

The FA*24/f2.0 also has a tendency to exhibit a similar charactaristic, but is less severe, but as it's an f2.0 lens it does show more readily. This is why some people claim it is soft at wide apertures, usually it is slightly OOF. Here is the test at f2.0.

Unless Pentax feature the same kind of menu focus calibration settings as allowed by the new C*n*n 1D mkIII (which they could do, the capability is in the debug subset. Maybe they will see fit to bring it in as a firmware update?), the lens itself will probably need to be re-calibrated.

FotoPete · 03-05-2007, 08:59 AM

Wow, so technical haha. it will be a long time till I actually get limited lenses.

benjikan · 03-05-2007, 09:03 AM

Originally posted by Richard Day

The DA 21 does seem to have a generic BF problem. I have tested 2 samples and they were identical. For most purposes it doesn't come into play as the DOF of the lens is quite large even at f3.2 and in many shots it will not be noticeable as the near limit of acceptable sharpness will be just within the focus point.

Here is a test at f3.2

At smaller apertures and with reasonably distant objects (as in the beach shot posted by Andy) it wouldn't show up, in fact it will give added depth of field behind the focus point which could be beneficial.

It will obviously be quite critical at close subject distances and at, or near, max aperture, which is how I suspect Ben is working with this lens.

The FA*24/f2.0 also has a tendency to exhibit a similar charactaristic, but is less severe, but as it's an f2.0 lens it does show more readily. This is why some people claim it is soft at wide apertures, usually it is slightly OOF. Here is the test at f2.0.

Unless Pentax feature the same kind of menu focus calibration settings as allowed by the new C*n*n 1D mkIII (which they could do, the capability is in the debug subset. Maybe they will see fit to bring it in as a firmware update?), the lens itself will probably need to be re-calibrated.

I was working at about 2.5 to 3 meters from the subject at f 9.0.

Ben

**jfdavis58** · 03-05-2007, 10:44 AM

FotoPete · 03-05-2007, 10:47 AM

haha if I get a Ltd, BF or FF is not going to be the first thing on my mind!

**tranq78** · 03-05-2007, 01:21 PM

That's a nice picture!

Richard Day · 03-05-2007, 03:46 PM

Originally posted by benjikan

I was working at about 2.5 to 3 meters from the subject at f 9.0.

Ben

Wow, that DA 21 must be waaay out!

Ask for a replacement!

The DOF at f9.0 and 2.5m distance is huge, basically everything should be sharp between 1.24m and infinity.

Check it out here: Online Depth of Field Calculator

03-05-2007, 05:45 AM	#1
benjikan Veteran Member Join Date: Jan 2007 Location: Paris, France Photos: Gallery Posts: 4,308	21mm Limited Back Focus Confirmed Just got the response from Pentax via their head office in Germany. They confirmed that there is a back focussing problem with the 21mm Limited exclusively. They offered to set up one of my bodies to work in conjunction with the lens, which I refused. I do not wish to take up one body exclusively for that lens. I am waiting on a firmware fix or a chip set change for the lens. I will use it in manual focus only. They are sending me back the two bodies and the two lenses i.e. the 21 and the 16-45 which didn't have a problem and focussed perfectly on the "0" calibration point. I will wait for the 16-50 f2.8 which I should have in ten days to use in lieu of the 21mm Limited. If it is anything like the Canon 17-40L lens which I used on 80 percent of my magazine work, I will probably do the same with it. Ben

03-05-2007, 06:15 AM	#2
amcinroy Junior Member Join Date: Feb 2007 Posts: 38	Thanks for posting the info Ben, I will keep my fingers crossed on a firmware fix rather than a chip fix. In the meantime, I was out using this lens at f8 at the weekend and wow, it's sharp. I will certainly be keeping it. Andy Last edited by amcinroy; 03-05-2007 at 06:24 AM.

03-05-2007, 06:38 AM	#7
benjikan Veteran Member Join Date: Jan 2007 Location: Paris, France Photos: Gallery Posts: 4,308 Original Poster	Why You? Originally posted by amcinroy Thanks for posting the info Ben, I will keep my fingers crossed on a firmware fix rather than a chip fix. In the meantime, I was out using this lens at f8 at the weekend and wow, it's sharp. I will certainly be keeping it. Andy Why You and Not Me? I guess 'cause you are shooting parallel to the subject...Nah, that is not the case as they tested mine and it was back focussing. I'm telling you it is my Karma for leaving Canon so abruptly. It is called the "CC" or the Canon Curse...

03-05-2007, 08:45 AM	#9
Richard Day Inactive Account Join Date: Feb 2007 Location: Gloucester UK Posts: 441	Originally posted by benjikan Just got the response from Pentax via their head office in Germany. They confirmed that there is a back focussing problem with the 21mm Limited exclusively. They offered to set up one of my bodies to work in conjunction with the lens, which I refused. I do not wish to take up one body exclusively for that lens. I am waiting on a firmware fix or a chip set change for the lens. I will use it in manual focus only. They are sending me back the two bodies and the two lenses i.e. the 21 and the 16-45 which didn't have a problem and focussed perfectly on the "0" calibration point. I will wait for the 16-50 f2.8 which I should have in ten days to use in lieu of the 21mm Limited. If it is anything like the Canon 17-40L lens which I used on 80 percent of my magazine work, I will probably do the same with it. Ben The DA 21 does seem to have a generic BF problem. I have tested 2 samples and they were identical. For most purposes it doesn't come into play as the DOF of the lens is quite large even at f3.2 and in many shots it will not be noticeable as the near limit of acceptable sharpness will be just within the focus point. Here is a test at f3.2 At smaller apertures and with reasonably distant objects (as in the beach shot posted by Andy) it wouldn't show up, in fact it will give added depth of field behind the focus point which could be beneficial. It will obviously be quite critical at close subject distances and at, or near, max aperture, which is how I suspect Ben is working with this lens. The FA24/f2.0 also has a tendency to exhibit a similar charactaristic, but is less severe, but as it's an f2.0 lens it does show more readily. This is why some people claim it is soft at wide apertures, usually it is slightly OOF. Here is the test at f2.0. Unless Pentax feature the same kind of menu focus calibration settings as allowed by the new Cnn 1D mkIII (which they could do, the capability is in the debug subset. Maybe they will see fit to bring it in as a firmware update?), the lens itself will probably need to be re-calibrated. Last edited by Richard Day; 03-05-2007 at 08:47 AM. Reason: changed a word for clarity*

03-05-2007, 09:03 AM	#11
benjikan Veteran Member Join Date: Jan 2007 Location: Paris, France Photos: Gallery Posts: 4,308 Original Poster	F9.0 Originally posted by Richard Day The DA 21 does seem to have a generic BF problem. I have tested 2 samples and they were identical. For most purposes it doesn't come into play as the DOF of the lens is quite large even at f3.2 and in many shots it will not be noticeable as the near limit of acceptable sharpness will be just within the focus point. Here is a test at f3.2 At smaller apertures and with reasonably distant objects (as in the beach shot posted by Andy) it wouldn't show up, in fact it will give added depth of field behind the focus point which could be beneficial. It will obviously be quite critical at close subject distances and at, or near, max aperture, which is how I suspect Ben is working with this lens. The FA24/f2.0 also has a tendency to exhibit a similar charactaristic, but is less severe, but as it's an f2.0 lens it does show more readily. This is why some people claim it is soft at wide apertures, usually it is slightly OOF. Here is the test at f2.0. Unless Pentax feature the same kind of menu focus calibration settings as allowed by the new Cn*n 1D mkIII (which they could do, the capability is in the debug subset. Maybe they will see fit to bring it in as a firmware update?), the lens itself will probably need to be re-calibrated. I was working at about 2.5 to 3 meters from the subject at f 9.0. Ben

03-05-2007, 06:21 AM	#3
Piotr Veteran Member Join Date: Jan 2007 Location: Warsaw Photos: Gallery Posts: 338	Andy, beautiful shot

03-05-2007, 06:25 AM	#4
RiceHigh Veteran Member Join Date: Nov 2006 Location: Hong Kong Posts: 1,934	But there was yet another DA 21 user who reported FF instead:- RiceHigh's Pentax Blog: DA 21 Limited Front Focusing or Back Focusing? Also, I cannot see how a firmware or chip upgrade can help to resolve the problem. I guess it is about the weaknesses of the Pentax AF system and/or the in-born optical errors, probably the spherical aberrations which cause the problem:- RiceHigh's Pentax Blog: AF Accuracy's Dependency on Lenses and Yellow Light Originally posted by benjikan Just got the response from Pentax via their head office in Germany. They confirmed that there is a back focussing problem with the 21mm Limited exclusively. They offered to set up one of my bodies to work in conjunction with the lens, which I refused. I do not wish to take up one body exclusively for that lens. I am waiting on a firmware fix or a chip set change for the lens. I will use it in manual focus only. They are sending me back the two bodies and the two lenses i.e. the 21 and the 16-45 which didn't have a problem and focussed perfectly on the "0" calibration point. I will wait for the 16-50 f2.8 which I should have in ten days to use in lieu of the 21mm Limited. If it is anything like the Canon 17-40L lens which I used on 80 percent of my magazine work, I will probably do the same with it. Ben

03-05-2007, 06:27 AM	#5
RiceHigh Veteran Member Join Date: Nov 2006 Location: Hong Kong Posts: 1,934	Originally posted by Piotr Andy, beautiful shot Yes, good mood, good composition and nice colors.

03-05-2007, 06:34 AM	#6
joele Veteran Member Join Date: Sep 2006 Location: Melbourne, Australia Photos: Gallery Posts: 1,308	As to the 21mm thats very interesting.. I had a lot of problems with the focus accuracy of the DA21 on my K100d but actually don't seem to have a problem with the K10d... weird.. will be interesting to see what Pentax do since they admitted the fault..

03-05-2007, 07:51 AM	#8
Alvin Veteran Member Join Date: Dec 2006 Location: Mississauga, Ontario, Canada Photos: Gallery Posts: 2,517	Ben, I'd be careful if you are considering going back to Canon after getting a Canon Curse. You may get a Pentax Curse, or does that exist? I don't want to jinx you.

03-05-2007, 08:59 AM	#10
FotoPete Veteran Member Join Date: Feb 2007 Location: Toronto Photos: Gallery Posts: 1,774	Wow, so technical haha. it will be a long time till I actually get limited lenses.

03-05-2007, 10:44 AM	#12
jfdavis58 Site Supporter Join Date: Nov 2006 Location: 13 S 0357397-3884316 Photos: Gallery Posts: 887	Wow

03-05-2007, 10:47 AM	#13
FotoPete Veteran Member Join Date: Feb 2007 Location: Toronto Photos: Gallery Posts: 1,774	haha if I get a Ltd, BF or FF is not going to be the first thing on my mind!

03-05-2007, 01:21 PM	#14
tranq78 Site Supporter Join Date: Dec 2006 Location: Canada Photos: Gallery Posts: 1,005	That's a nice picture!

03-05-2007, 03:46 PM	#15
Richard Day Inactive Account Join Date: Feb 2007 Location: Gloucester UK Posts: 441	Originally posted by benjikan I was working at about 2.5 to 3 meters from the subject at f 9.0. Ben Wow, that DA 21 must be waaay out! Ask for a replacement! The DOF at f9.0 and 2.5m distance is huge, basically everything should be sharp between 1.24m and infinity. Check it out here: Online Depth of Field Calculator

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