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03-27-2015, 06:00 PM   #16
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QuoteOriginally posted by ychousa Quote
Yeh, I guess I probably have to do it if this is something very unusual. In this kind of case, do the lens and camera should be all new and under warranty? or just the camera is under warranty and I can include any old lens? Do you know by chance?
I would include a lens you know to be working (like I said, check it on someone else's body) and say, "Something here isn't right. Make it work. Set it so this lens works perfectly with zero AF adjustment." So no I wouldn't send them any old lens, I'd send them one you (want to) use a lot. You don't have to send a lens, it just helps them reproduce your problem with the same equipment and gives them a calibration target.

03-27-2015, 06:09 PM   #17
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QuoteOriginally posted by ychousa Quote
it badly front-focuses on a distant subject at f1.8
Would you like to describe how you evaluate front focus on a distant subject? -10 setting is a huge difference in plane of focus when any distance is involved (e.g. more than about 50 meters).


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03-27-2015, 06:10 PM   #18
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QuoteOriginally posted by vonBaloney Quote
Or send camera AND lens in for service and tell them to check everything and recalibrate the AF system...
Probably the best suggestion on this thread.


Steve
03-28-2015, 04:14 AM - 1 Like   #19
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My experience

I had some lenses that cant focus correctly with my k-5II. I do many corrections, test shots, etc, but with no succes.
So, I call to our local Pentax repair centre - they told me, that it can be camera fault - So I take five my most used lens and camera and take it to repair centre. They test it and - yes - camera has slight missfocus - nothing to notice with f-stop 3.5 and higher. They send my 5 lenses and body to France to racalibration (body is under warranty, some lenses are, some not - but all brand Pentax) - and now it is razor accurate. Nice. Even my 100 Macro is even better then before The very helpfull srvicemen told me, that people usually do they af callibration wrong way - and make it worse. And often it is camera problem - and with calibrated camera it turns to no (or verry little) need to calibrate lenses.

Also, I have DA 50 1.8 with no excessive hunting problem. Problem is that center AF point is 2.8 accuracy and lens is 1.8...

But, in the other hand, some my lenses (that are calibrated) need more that -10 coorection on my K-r body (need to acces service menu)! And my DA40 dont focus correctly anyway... Then I realized, that my DA40, when focusing really close - is focusing slightly off. And I tested and calibrate it in close distance. - So, I calibrate my camera with my razor sharp DFA100, then put on it back DA40 - and voila! Focus is right!

BTW: I have allways problems with sigma lenses on my Pentax cameras - must return 18-35 and 30 1.4 C becouse focusing issues. But, to be honest, I must return DA20-40ltd due to decentring issue, so even in Pentax high grade lens arent everything ok.

So my advice - send to calibration all your Pentax lenses, which is for you importatnt, with your body. In Europe must be in warranty only body, if lenses are brand Pentax.

03-28-2015, 05:49 AM   #20
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Addressing your thread title, I'm aware of no objective study that concludes that Pentax gear has a higher rate of defects than the industry norm.

With respect to your DA 50, when testing for focus accuracy, your subject distance should be 50 times your lens focal length (2.5 meters for the 50mm lens).

I recommend this method for checking focus accuracy: AF microadjustment for the 1Ds mark III, 1D Mk3, 5D Mk2, 7D, 1D X
03-28-2015, 06:38 AM   #21
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In an attempt to alleviate the OP's loss of confidence in buying Pentax-branded or K mount third-party lenses, here are some of the conclusions Roger Cicala over at lensrentals.com drew from their 2012/2013 repair data. He and his team should know, I suppose. At the time they hadn't carried Pentax lenses long enough to include them in their evalutions, but as a tentative statement about the industry as a whole it should still hold some interest:
  • Every manufacturer has some great lenses and some weak lenses.
  • 70-200 f/2.8 lenses are likely to fail no matter who makes them. We think of them as 'built like tanks' because they have that heavy, all-metal case. That case, though, is as packed with mechanics and electronics as anything you've ever seen. There's a LOT of stuff in there that has to work perfectly. Inevitably, some of that stuff breaks.
  • Sigma's big zooms still have trouble with their HSM motors and OS units, but Sigma really does seem to be doing better. Their large zoom lenses are still on the list but the frequency is lower than it used to be, in a year when my new accounting system made most numbers look worse. Sigma's prime lenses and smaller zooms have excellent repair rates.
LensRentals.com - Lensrentals Repair Data: 2012-2013

I'm personally running my second Pentax DSLR now (a K-3, which succeeded a K-7), with meanwhile four genuine Pentax DA lenses, two zooms and two primes, and (knock on wood!) haven't yet encountered a major issue with any of them, although I'm fairly picky regarding IQ und guilty of the more than occasional pixel-peeking. None of those lenses is perfect, and the kit lens is noticeably weaker than any of the other three, but I know from experience that they are all good enough for gorgeous A3 prints, and have been so without any adjustments. Maybe I've been lucky, but my strategy of buying new from trusted sellers - even if this means that I have to wait a little longer for my next lens - seems to have paid off so far.
03-28-2015, 06:59 AM   #22
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Jannis makes an excellent point. If you send in a lens, make it a fast one (so the 1.8 is a good choice). And yeah, should probably be a Pentax lens...
03-28-2015, 07:39 AM   #23
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It looks to me there was nothing wrong with your copy of Fa 50/1.7 most primes don't change focus, there's some focus breathing sometimes that's affected by aperture changes...Samyang 85/1.4 does this...

03-28-2015, 09:04 AM   #24
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QuoteOriginally posted by Jannis Quote
I had some lenses that cant focus correctly with my k-5II. I do many corrections, test shots, etc, but with no succes.
So, I call to our local Pentax repair centre - they told me, that it can be camera fault - So I take five my most used lens and camera and take it to repair centre. They test it and - yes - camera has slight missfocus - nothing to notice with f-stop 3.5 and higher. They send my 5 lenses and body to France to racalibration (body is under warranty, some lenses are, some not - but all brand Pentax) - and now it is razor accurate. Nice. Even my 100 Macro is even better then before The very helpfull srvicemen told me, that people usually do they af callibration wrong way - and make it worse. And often it is camera problem - and with calibrated camera it turns to no (or verry little) need to calibrate lenses.

Also, I have DA 50 1.8 with no excessive hunting problem. Problem is that center AF point is 2.8 accuracy and lens is 1.8...

But, in the other hand, some my lenses (that are calibrated) need more that -10 coorection on my K-r body (need to acces service menu)! And my DA40 dont focus correctly anyway... Then I realized, that my DA40, when focusing really close - is focusing slightly off. And I tested and calibrate it in close distance. - So, I calibrate my camera with my razor sharp DFA100, then put on it back DA40 - and voila! Focus is right!

BTW: I have allways problems with sigma lenses on my Pentax cameras - must return 18-35 and 30 1.4 C becouse focusing issues. But, to be honest, I must return DA20-40ltd due to decentring issue, so even in Pentax high grade lens arent everything ok.

So my advice - send to calibration all your Pentax lenses, which is for you importatnt, with your body. In Europe must be in warranty only body, if lenses are brand Pentax.
Hi, Jannis. your comment is really helpful along with others'. Because my camera works perfectly with my DA 35mm f2.4, I kind of ruled out the possibility of camera fault-still don't understand how it's possible that it works with one lens perfectly but it looks like this camera might really need service. What would be an estimated time frame to receive the camera back?-I live in Southern CA, US. I read somewhere that it took 2 months or so, or service center didn't really do anything, etc.. so is there a tip to get the right service? It looks like the quality of service varies depending on where you live? Not sure, but I hope I could really resolve this problem.
03-28-2015, 09:09 AM   #25
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QuoteOriginally posted by MPrince Quote
Addressing your thread title, I'm aware of no objective study that concludes that Pentax gear has a higher rate of defects than the industry norm.

With respect to your DA 50, when testing for focus accuracy, your subject distance should be 50 times your lens focal length (2.5 meters for the 50mm lens).

I recommend this method for checking focus accuracy: AF microadjustment for the 1Ds mark III, 1D Mk3, 5D Mk2, 7D, 1D X
Thank you for stating the obvious regarding Pentax lenses and for your sound advice regarding testing.

Yes, 50x the focal length is a good general test distance. I have used the moire' test you linked to and can attest that it is a good method. It was the moire' test that eventually convinced me to stop fiddling with endless AF adjustment.

Here are several points related to AF testing in general:
  • It is imperative that the focus target be perpendicular to the lens axis and that the area being evaluated be large enough to fully engage the AF focus point
  • AF testing at long distance is a waste of time due to both optical and mechanical considerations. I won't go into detail here. PM me if you want to know more.
  • If using other than the moire' test linked above, use magnified live view with focus peaking to evaluate OOF condition as well as whether it requires + or - to correct
  • Do a minimum of 10 tests from infinity down and 10 tests from MFD up before deciding whether adjustment should be applied and to determine the direction (+ or -)
  • Work in one-step increments when doing the adjustment and do a full recheck (down and up) after each step. When the number OOF "-" is the same as "+", you are dialed in. How far off is not a consideration.
  • It is often helpful to work from a known in-focus state using CDAF (live view) or manual focus (magnified live view w/ focus peaking) and seeing whether the PDAF system attempts to focus + or - from the point of known good focus
Is this tedious enough yet?


Steve
03-28-2015, 09:15 AM   #26
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It is always possible I suppose that your AF sensor is just dirty, I have never had trouble with that but some people have said they get a speck or something on the AF sensor and it throws everything out of whack. Haven't been leaving your camera sitting around with no body cap on filling up with dust, have you?
03-28-2015, 09:23 AM   #27
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QuoteOriginally posted by Stavri Quote
there's some focus breathing sometimes that's affected by aperture changes...Samyang 85/1.4 does this...
The term is seldom used on this site, but "focus breathing" usually is described as a change in relative FOV as the lens focuses down from infinity. The term is a bit of a misnomer and is a property of many internal focus zoom lenses. For example, my Sigma 17-70 FOV at 70mm and 2 meters is about the same as a 50mm lens at the same distance.

http://www.bobatkins.com/photography/technical/focus_breathing_focal_length_changes.html

What you are describing is called "focus shift". It is caused by residual spherical aberration and occurs when the lens stops down at exposure time. Usually, the shift is relatively small (a few millimeters +/- at plane of focus at common shooting distances) and is covered nicely by increased DOF. Where it becomes a problem is when doing macro work.


Steve

Last edited by stevebrot; 03-28-2015 at 09:30 AM.
03-28-2015, 09:35 AM   #28
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QuoteOriginally posted by vonBaloney Quote
It is always possible I suppose that your AF sensor is just dirty, I have never had trouble with that but some people have said they get a speck or something on the AF sensor and it throws everything out of whack. Haven't been leaving your camera sitting around with no body cap on filling up with dust, have you?
No, I haven't left my camera with no body cap. Never changed lens outside. When I changed lens at home, I quickly changed it without leaving it uncovered for more than 5 seconds. But I'll try to air-blow the sensor in case though-I have a pretty fluffy pomeranian dog with lots of hair to share. My plan is to air-blow sensor first, exchange this 50mm second because this one does look like it has a focusing problem, then send this camera to service center. Any advice for additional or missed step? BTW, I truly truly want to thank you for your folks help-I'm very impressed and feel so happy that I'm in this community
03-28-2015, 09:41 AM - 1 Like   #29
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QuoteOriginally posted by ychousa Quote
What would be an estimated time frame to receive the camera back?-I live in Southern CA, US. I read somewhere that it took 2 months or so, or service center didn't really do anything, etc.. so is there a tip to get the right service? It looks like the quality of service varies depending on where you live? Not sure, but I hope I could really resolve this problem.
In the U.S., warranty work is done by Precision Camera in Connecticut*. My experience (one camera) was that the work (replacement of the mirror controller on a K-50) was done in a timely manner (two days) once the warranty claim was approved by Ricoh. If parts are required that are not part of normal stock, the time will be longer.

The main issue, according to users on this site, is getting the payment authorization from Ricoh as well as determining the true status of the work order on the Precision Camera Web site. Precision could do better in communication and Ricoh should definitely do better in tracking warranty work.


Steve

* Requires proof of purchase from an authorized N. American vendor and must be shipped from within the U.S.
03-28-2015, 09:49 AM   #30
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QuoteOriginally posted by stevebrot Quote
In the U.S., warranty work is done by Precision Camera in Connecticut*. My experience (one camera) was that the work (replacement of the mirror controller on a K-50) was done in a timely manner (two days) once the warranty claim was approved by Ricoh. If parts are required that are not part of normal stock, the time will be longer.

The main issue, according to users on this site, is getting the payment authorization from Ricoh as well as determining the true status of the work order on the Precision Camera Web site. Precision could do better in communication and Ricoh should definitely do better in tracking warranty work.


Steve

* Requires proof of purchase from an authorized N. American vendor and must be shipped from within the U.S.
Hi, Steve, thanks alot for the information! I'll follow the troubleshooting root that I wrote and see how it goes.
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