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11-30-2013, 01:50 PM   #31
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I suspect repairing the 60-250 isn't for the faint of heart and requires an exceptional technician.

Weather-sealed zoom optics are incredibly complex.

11-30-2013, 07:49 PM   #32
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More tests: At 10 ft from the subject, f/8, most of the frame is sharp--except for slight softness at the far right side. The depth-of-field calculator app on my Nexus 7 tells me that there is 0.86 inches of depth of field. However, even after adjusting for angle errors and focusing on the far right point, the right 15% or so of the frame is marginally softer than the rest of the frame.

This lens is supposed to be uniformly sharp across the frame. If this kind of softness is visible at f/8, then something has got to be wrong. The lens is decentered. Though not as severely as initially reported, it is still not acceptable for a lens of this caliber.

Edit: Further tests 12 ft from a different but known flat subject at f/4 with slightly varying angles as well as verified correct angles to the subject all indicate that the lens is decentered. The best result obtained after more than 20 test frames was full sharpness across 85% of the frame, with a rapid drop-off in sharpness in the right 15%.

There's no need for further testing. Even after accounting for possible testing errors, one thing is for certain: the lens is decentered. Period, end of story.

--DragonLord

Last edited by bwDraco; 11-30-2013 at 08:20 PM.
12-01-2013, 06:35 AM   #33
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QuoteOriginally posted by DragonLord Quote
the lens is decentered. Period, end of story.
What do you plan to do about it?
12-01-2013, 07:43 AM   #34
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The question becomes where do you find a qualified lens technician. An article recently linked to on the forum, from a blog over at Lensrentals, they write about this issue rather extensively. They've found it's not just Pentax, it's all camera companies. Companies have the ability to calibrate center sharpness, most cannot reset a decentred lens. The guys a Lensrental, just on a whim, spent two hours on a decentered lens and got it back to pretty good, just using trial and error. Surely there is somewhere you can send a good lens to have it re-aligned. Back when I was in school in the 60s, the advice was to toss the lens. The lenses were often held in place with cardboard mounts, lens technicians were rarely able to make adjustments that brought the lens back into the correct alignment. Maybe something is changed, I don't know, but, you do have a couple weeks to return something if you feel it's defective... I did so with two Sigma 120-400s. I still don't know if the lenses were defective or just really soft. I moved on to the 60-250. My point being, if you received a good lens, it should still be good. If you didn't you should have returned it. When I get a new lens, I take the first few weeks to put it through it's paces. If there seems to be anything wrong, I return it.

One of the points made at Lensrentals is most lenses are returned to the customer claiming they are within spec, but no one knows what "within spec" means. It seems to mean if they can get the lens center sharp then that is within spec.

It's just a bummer, you can't just return it. I'm sure we'd all like it if Pentax just gave you a new lens, if there was a petition, I'd sign it.

12-01-2013, 10:15 AM   #35
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QuoteOriginally posted by snake Quote
What do you plan to do about it?
12-01-2013, 10:19 AM   #36
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QuoteOriginally posted by DragonLord Quote
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Well at least you have their attention. I wonder if they are testing lenses to see if what they have in stock to see if any they have are better than what you have. I'm betting 99% of users who buy a 60-250 wouldn't do the tests you've done.
12-01-2013, 05:38 PM   #37
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The SDM recently failed on my 60-250 and my initial contact with CRIS wasn't encouraging. The repair bill of materials listed someone else's equipment, name and address. I think I will live with manual focus for awhile to see if your experience improves before I head down the same path. Best of luck with your lens.
12-01-2013, 08:29 PM   #38
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This type of post makes me a bit uncomfortable, since my 50-135 is in CRIS's hands... for focus issues...

12-01-2013, 09:36 PM   #39
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QuoteOriginally posted by Aggie89 Quote
The SDM recently failed on my 60-250 and my initial contact with CRIS wasn't encouraging. The repair bill of materials listed someone else's equipment, name and address. I think I will live with manual focus for awhile to see if your experience improves before I head down the same path. Best of luck with your lens.
Have you considered deactivating the SDM so that it will focus using the screwdrive? Apparently this is easy to do if you have access to an older body like a K-7 or K20D (which is used to reprogram the lens). It will then focus using the screwdrive on all bodies, including the K-3. This seems like a better approach than living with only manual focus. I have read that some people are doing this to SDM lenses that are working perfectly in order to take advantage of the faster screwdrive focus in the K-3. Supposedly the conversion results in a noticable improvement in focusing speed. Of course it is noiser, but I would prefer faster focusing over quieter focusing. If I had a 60-250 I would convert it to screwdrive focus even if the SDM were working. In your case it seems like a no-brainer given that the SDM is shot.

Dan

Last edited by Dan; 12-01-2013 at 09:42 PM.
12-02-2013, 06:30 AM - 1 Like   #40
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.... but as I understand it, the lens was new - now 6 months old. It should just work. This is something refereed to as merchantability - its a concept in consumer law that basically says, you buy something and it should work for its stated purpose. You buy a new lens, it should focus across its designed focal length range.

Pentax should monitor the products as they flow through at CRIS for items that go through there multiple times that are new within the warranty period. Things that go back for a second time within the year should get flagged - a weekly report to the VP (the information is already in the database - just mine it, simple enough). This is the beginning of a trend analysis. If there is a bunch of XXXX (you name it) that starts to trickle in, and then some additional units, there is a manufacturing problem. If its just a single unit bouncing back - then its a lemon (or the beginning of a trend). In either case it is something that needs to be attended to both on the customer front (swap it out), and in manufacturing.

This is not a new process or a recent discovery. This is basic manufacture engineering - it goes all the way back to Demming.

What you don't want is another 16-50 debacle that just drags on for years - essentially killing the produce in a slow death spiral. Fix the design, identify the part, the assembly process, the QA/QC - whatever the problem turns out to be.. In order to do that you need to understand, identify that you have an inherent problem(s), and identify and localize it/them. For that you need bad sample units. This is not rocket science. This is basic product management.

Right now the DA * 60-250 has a sterling reputation. This happens, and now a few folks who have just bought it or are thinking about buying it are starting to question what they should do - and should they buy it or not. Plus, its the holiday season that the majority of buying is done in. It can be a good year or a bad year based on the last 60 days. Why put all of that in jeopardy and at risk.

Cost - sure it looks like it may be an expensive proposition at first, but you fix the product - and you make it back up in sales, or kill the product so that you no longer have to support it and have it suck the life out of you if you are unwilling to fix the problem. The first unit with the problem is a lemon, the second one (depending on the amount of time since the first), may also be a lemon. Just replace them. When you start to have a number of units come in - it is a problem that needs to be recognized and attended to.

And it is just not a Pentax problem. Look at Nikon with the D600 with the oil film that turns into a dust and dirt issue. They never really did anything about it - finally a cleaning, then replaced it with the D610 which included a very small feature upgrade just to save face.

This one single thread is now 35 days old. Its the second thread on the OP's lens. This should have been addressed and fixed 30 days ago - with the OP posting images and saying how great the lens is and how Pentax did the right by him. The OP should be out with his lens this last week shooting images (or studying for midterms) - rather than waiting for a phone call from on high. Instead he is cooling his heels waiting on a call.


Last edited by interested_observer; 12-02-2013 at 06:37 AM.
12-02-2013, 07:58 AM   #41
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Here's a good reference article just so you understand what you're up against…
LensRentals.com - There is No Perfect Lens

And another…
inspecting-an-in-spec-lens
12-02-2013, 10:21 AM   #42
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The lensrentals.com blogs are a good read. I wouldn't be surprised if it's impossible to obtain factory-authorized lens calibration in the US for Pentax. CRISCAM may not even have the equipment/expertise necessary to calibrate Pentax glass.

If the above is true, this is one more reason why Pentax cannot command higher-end Canon/Nikon prices.
12-02-2013, 10:27 AM   #43
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QuoteOriginally posted by krebsy75 Quote
The lensrentals.com blogs are a good read. I wouldn't be surprised if it's impossible to obtain factory-authorized lens calibration in the US for Pentax. CRISCAM may not even have the equipment/expertise necessary to calibrate Pentax glass.

If the above is true, this is one more reason why Pentax cannot command higher-end Canon/Nikon prices.
He's talking mostly about Canon and Nikon, who clearly can command high prices despite not being any better than anyone else. The other thing you can get from the lensrenatal site, Pentax lenses have the best reliability rating. If you end up actually paying attention to what lens rentals say, you might end up wondering why Pentax does't charge more.
12-02-2013, 11:26 AM   #44
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The point I was trying to make is that it might be easier to service Nikon/Canon glass than Pentax in the US. If this is the case, higher asking prices may be warranted for those brands.

QuoteOriginally posted by normhead Quote
He's talking mostly about Canon and Nikon, who clearly can command high prices despite not being any better than anyone else. The other thing you can get from the lensrenatal site, Pentax lenses have the best reliability rating. If you end up actually paying attention to what lens rentals say, you might end up wondering why Pentax does't charge more.
12-02-2013, 07:22 PM   #45
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QuoteOriginally posted by Dan Quote
Have you considered deactivating the SDM so that it will focus using the screwdrive? Apparently this is easy to do if you have access to an older body like a K-7 or K20D (which is used to reprogram the lens). It will then focus using the screwdrive on all bodies, including the K-3. This seems like a better approach than living with only manual focus. I have read that some people are doing this to SDM lenses that are working perfectly in order to take advantage of the faster screwdrive focus in the K-3. Supposedly the conversion results in a noticable improvement in focusing speed. Of course it is noiser, but I would prefer faster focusing over quieter focusing. If I had a 60-250 I would convert it to screwdrive focus even if the SDM were working. In your case it seems like a no-brainer given that the SDM is shot.

Dan
I am considering converting to screwdrive. I have a K-200 and a K-5. Just need to find the time and nerve. Seeing others experience trying to get SDM fixed should solve the nerve part.
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