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04-02-2011, 07:45 AM   #1
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DA Limited, varying build quality from sample to sample.

Now, before i get the "hellraiser" stamp on me, just continue reading

I recently got an used DA 70 at a very good price.

Before we contionue we have to seperate two things. With "focus barrell" i mean the lens group assembly. Not the focus ring barrell

My sample has an wobble that isnt very much, but its audible when handling the lens of camera. Sounds like something is loose. So i had a closer look myself! Now, i dont recomend anyone to do this. I didnt even bother to take pictures because i had to focus on what i was doing

The focus barrell lens group of the DA 70 is designed to take out as one whole piece, there is no point going in from the front, that only reveals the front element.
I went in from the back taking of the black plastic cover, mount, contacts (not very fun to do), aperture control.

Looking at the back i now had a very nice view into the whole lens. I noticed that on each side of the lens group there was two small L-shaped metall parts with the long ends running between the lens group thread (cutouts in the thread) and focus ring thread. They hold the lens group into its non rotating position. Removing these makes it posible to rotate out the lens group.

Now with the lens group out of the lens house the thick threads on its outside is visible, and looking into the lens house itself one can see the corresponding threads that is part of the focusing ring.

This was what i was curious about! Was anything in there loose?
The threads on the inside of the lens house is made in one piece with the focus ring, so if the focus ring has no wobble, you dont need to worry, and dont need to do stupid things like i do If the lens group falls out of from the house, those L-brackets has loosened (that has happened to some)

So, the "lens group barrell wobble" can only depend on ONE thing only.
And that is tolerance in the focus thread of both lens group part and focus ring part.


My sample is quite loose, and some others have thight ones. In my sample there is no grease or anything in those threads. I guess that would be the only way to make the lens group not to wobble. Or get another one....

Now your are thinking, "i could have told him that", but in the other posts about this i see people saying "Send it in, mine is tight", "Its normal, mine has a wobble to" and "All lenses wobble to some degree". So i just decided to look for my self!

Thats all. If you buy a new one that has wobble, request a new one! I would!


04-02-2011, 07:48 AM   #2
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hellraiser!
04-02-2011, 12:01 PM   #3
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QuoteOriginally posted by dgaies Quote
hellraiser!
No, you are not a hell raiser. The DA lenses are optically excellent but mechanically, they and 90% of other branded lenses made today, are not as well constructed as the Taks from the 60's and 70's. We can thank inflation for that.
04-02-2011, 12:25 PM   #4
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Mine doesn't wobble!



[I just had to say that ]

04-02-2011, 12:30 PM   #5
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By the way, did you manage to put it back together, with less wobble than before?
04-02-2011, 12:55 PM   #6
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QuoteOriginally posted by maciek_w Quote
By the way, did you manage to put it back together, with less wobble than before?
Haha! Yes i got it back together Its not a complex lens house design like most manual lenses with exeption of SD shaft and gearing and of course a electric board with contacts through the mount.

The electric contacts with the small (very very very small) springs was the only part hard to get back

As far as wobble, still the same wich i knew the moment i found the cause. Only thing to do is aply some kind of thick grease. But thats a no no for me....

I thought of not posting this at all, felling kinda silly about it. But if someone buys a Ltd lens and have the same issue, they'll likely find this. And instead of asking questions and get mocked (yes, theres sometimes alot of it here) they can read this

Last edited by the swede; 04-02-2011 at 01:04 PM.
04-02-2011, 01:04 PM   #7
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Would make sense to suggest making this post a sticky, maybe?
04-03-2011, 11:31 AM   #8
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QuoteOriginally posted by the swede Quote
As far as wobble, still the same wich i knew the moment i found the cause. Only thing to do is aply some kind of thick grease. But thats a no no for me....
Wouldn't thick grease just increase the torque load on the screw-drive motor? That doesn't sound like a good idea.

04-04-2011, 10:00 AM   #9
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QuoteOriginally posted by Hound Tooth Quote
Wouldn't thick grease just increase the torque load on the screw-drive motor? That doesn't sound like a good idea.
Dont know

But i do know that the focus ring turns very easy on this lens.
04-04-2011, 10:36 AM   #10
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I knew a guy who had all kinds of mechanical problems with a Mercades. It can happen, though I suspect the percentages of Limites with sloppy gears (so to speak) is rare. One of the biggest selling points of the Limiteds is build quality and smooth focus rings. What you experienced, I think, is unacceptable, and is probably why you got it at "a very good price."
Generally, the build quality of Limiteds is very good, only surpassed by Zeiss at twice the price.
04-04-2011, 11:12 AM   #11
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QuoteOriginally posted by Ron Kruger Quote
One of the biggest selling points of the Limiteds is build quality and smooth focus rings. What you experienced, I think, is unacceptable, and is probably why you got it at "a very good price."
Generally, the build quality of Limiteds is very good, only surpassed by Zeiss at twice the price.
Well.... it doesnt turn by it self, but its not as damped as the DA 40. My DA 15 and DA 70 feels the same, but the DA 15 barrel doesnt wobble.

New price for DA 70 in Sweden is about 880$
I got this one for 475$ wich is about the avarage used price on the market.

Still think i made a good deal, and if i have the chance i'll someday try another to see the difference.

This lens is sharp and focuses correct, so im still happy with it
04-04-2011, 03:39 PM   #12
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How can you generalize about the build quality given that your copy of the DA70 was a used one and basically not new? You can't be sure whether the previous owner had abused it or not. Test with a new copy and use it extensively and perhaps that would be more conclusive for that particular copy. Didn't experience any wobble on my DA70.
04-04-2011, 09:32 PM   #13
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QuoteOriginally posted by creampuff Quote
How can you generalize about the build quality given that your copy of the DA70 was a used one and basically not new? You can't be sure whether the previous owner had abused it or not. Test with a new copy and use it extensively and perhaps that would be more conclusive for that particular copy. Didn't experience any wobble on my DA70.
I think it's pretty easy to tell whether the threads on the focus mechanism have been abused in some way. There's not much magic to it. I'm not surprised to learn that there are such wide levels of tolerances in the build quality. I think one advantage that Japanese workers had when assembling Pentax lenses was an ability to set aside parts with varying tolerances and match them up with other parts so that the resulting product had a better fit. Based on what has been reported with regard to FA Limited lenses, this skill is not as present in the Vietnam assembly line workers. Or perhaps the parts for DA Limiteds aren't built to the same strict tolerances that FA Limiteds were once upon a time.
04-04-2011, 11:40 PM   #14
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QuoteOriginally posted by creampuff Quote
How can you generalize about the build quality given that your copy of the DA70 was a used one and basically not new? You can't be sure whether the previous owner had abused it or not. Test with a new copy and use it extensively and perhaps that would be more conclusive for that particular copy. Didn't experience any wobble on my DA70.
Im not generalizing anything, i know the person i bought it from. Dont feel the need to convince you about anything more than that.

If you think about it. Lets say you have a DA 70 wich has no wobble or play from the threads. What type of usage will make the threads grind up?

I guess if you put the lens into a machine that turns the focus barrel continous and fast 24 hours for a very long time, then yes.... maybe they would wear out.

QuoteOriginally posted by Hound Tooth Quote
I think it's pretty easy to tell whether the threads on the focus mechanism have been abused in some way. There's not much magic to it. I'm not surprised to learn that there are such wide levels of tolerances in the build quality. I think one advantage that Japanese workers had when assembling Pentax lenses was an ability to set aside parts with varying tolerances and match them up with other parts so that the resulting product had a better fit. Based on what has been reported with regard to FA Limited lenses, this skill is not as present in the Vietnam assembly line workers. Or perhaps the parts for DA Limiteds aren't built to the same strict tolerances that FA Limiteds were once upon a time.
Good post!
04-04-2011, 11:49 PM   #15
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There´s varying build quality in everything, of course there is. When I got a DA70 it was optically perfect but the quick shift would seize up continually & when in AF it would struggle to find focus even in good light with a high-contrast subject. I took it back, but at some time in the future I would like to buy another one, and I won´t worry too much about getting a dud.
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