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05-03-2009, 07:55 PM   #16
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No ! But if you don't care about SDM, you can use them forever in Manual Mode !

05-03-2009, 08:05 PM   #17
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QuoteOriginally posted by alohadave Quote
What goodwill would that engender? Just because it's a small item doesn't make it practical to be user replaceable. You'd still need to open the barrel of the lens to get to the motor.
Hey ... having to open up the barrel would not be what I term user-replaceable.

I'm sure Pentax clever engineers can design for the motor to sit under a flap door which needs just a screwdriver to open, and the motor itself is pull-out plug-in like replacing a light bulb ... easy
05-03-2009, 09:05 PM   #18
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QuoteOriginally posted by creampuff Quote
Sorry but talking about legacy lenses is a different context altogether to a modern AF lens, which is frankly quite a lot different construction wise. For one thing, lenses today have to factor in AF. Lens designers have to contend with the size and weight of the focusing ring and focus throw as it has a bearing on the load and inertia the focusing motor has to overcome.

If one were to open up an SDM lens, you will be very surprised to find that the SDM motor is about the size of a button or small coin. My take is some of the SDM lens failures we hear about is probably because early production SDM lenses had not so robust motors. Talking with my local Pentax agent, those lenses that had these SDM issues were sent back to Japan and had their motors replaced with new ones with no subsequent issues arising. One of the early adopter pitfalls.... heck I just recently saw with my own eyes a Sony user's new Sony A900 had its mirror lock up rendering the camera useless... apparently a known issue.

One thing I know is the DA* lenses are pretty solid in build quality, which I can't really say for the DA and some DA Limiteds, the common loose and wobbly lens barrels come to mind.
Sorry to be so obtuse

My entire point is all the gimmicky, electronic motor stuff doesn't change the fact that glass transmits light - that hasn't changed at all.

I find it interesting that we want the durability of a brass and aluminum, lubricated, manually-operated device. Yet we expect that from a device that has nano-wires on circuit boards, motors with self-lubricating, enclosed bearings, machine solders rather than hand-assembly, etc. - and expect it to cost about the same in inflated dollars as a lens did in 1965. All the "improvements" have a cost - loss of durability.

A good 50/1.4 cost about $75 in 1965 - a Spotmatic with kit Super Tak 50/1.4 lens cost $300. The lens would be $506 today. The Kit would be $2,026 today.

A 43 Limited costs around the inflated value of a Super-Tak, and it doesn't have an SDM motor. DA lenses aren't built to last 40 years - to build them that way would be prohibitively expensive.

The problem isn't the lenses - the problem is our expectations of the lenses. If we want a lens that will last 40 years, as the Takumars have, we should be willing to pay $500 just for the durability - then add money for all the improvements, remembering that the improvements also must be durable - therefore expensive. It should be possible to build HyperSonicMotors that would turn a heavy barrel with a long focus throw very quickly - but it isn't possible to build one for the same inflated price as a Super Takumar. Thus we use lighter, less durable parts, small motors, plastic barrels - even plastic mounts - to keep price parity with kits all the way back to the 60's.

Last edited by monochrome; 05-03-2009 at 09:11 PM.
05-03-2009, 10:19 PM   #19
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Based on the reports on this forum, in some cases, SDM stops working after the lens is stored for a while. Maybe, their longevity depends on how you store them.

05-03-2009, 10:32 PM   #20
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QuoteOriginally posted by regor Quote
No ! But if you don't care about SDM, you can use them forever in Manual Mode !
"It's a fool who looks for logic in the chambers of the human heart."

So expect people to write how they expect their manual focus lenses to outlast the SDM motor of their DA* lenses.
05-03-2009, 10:41 PM   #21
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QuoteOriginally posted by ABCWinter Quote
But I am wondering should I scrap the DA*200 and get glass that will last as long as I live, or gamble with the DA* lense ?
DA* 200 f/2.8:



FA* 200 f/2.8:


You should first ask yourself whether the optics of these lenses is good enough for you. The problem with older telephoto lenses is chromatic aberration--but, I guess, you can fix that in post-processing.
05-03-2009, 10:45 PM   #22
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Dismantling a lens may be easy enough but unless one has the right tools and know exactly what needs to be done, it is a job better left with the authorized repair facility. My local Pentax agent doesn't even dismantle the SDM motor but ships it back to Japan. I am sure Pentax will have made continual improvements on the quality of the SDM motors during assembly as such repairs actually incurs more time and expense to rectify later.
05-04-2009, 09:38 AM   #23
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QuoteOriginally posted by Robert S Donovan Quote
Just did a bit more research on SDM technology. Coming from Canon like I did, I just assumed SDM was an ultrasonic ring motor like Canon pioneered 20 years ago. Turns out I was wrong. Pentax's SDM technology is actually an ultrasonic drive motor connected to the screw drive shaft. My guess, all of the torque on that tiny motor is just too much for it to bear. A traditional ring type ultrasonic motor is much more robust as it spreads the torque load out around the entire perimeter of the lens barrel.
I see the part of the problem in insisting the screw drive to remain on SDM operated lenses - this makes the whole construction mechanically more complicated (and thereby more prone to failures) and may be one of the reasons why Pentax does not use ring-type ultrasonic drive in SDM-equipped lenses. It can be also the source of other shortcomings like AF speed etc.

If somebody thinks that the screw drive can be a salvation if SDM fails, then... it just may not be the case - at least not always, because failure can render the whole focus mechanism inoperable i.e. neither manual focus nor screw drive wouldn't work. We have few examples described here on the forum with this "stuck focus mechanism" issue. I myself had a luck to acquire DA* 50-135 recently and had one of these "heart-missing-a-beat" moments, when focus mechanism was "stuck". It started by camera suddenly trying to operate a screw drive and failing at it. Then I tried to rotate focus ring: it was stiffer - just like on rotating beyond focusing limits - and focus mechanism was almost completely stuck...

Then I turned camera off and mounted other lens on it to take some pictures. Then I noticed, that unmounting the lens solved this "sticking" and remembered that I mounted it on camera without switching the camera off this time. It just can be possible, that AF controller or the firmware in the body got "confused" and the SDM drive got into some kind of abnormal "intermediate" state, where it was activated bot not rotating - which just made MF inoperable and focus mechanism to feel "stuck" - just like SDM has taken the focus mechanism over but not doing anything with it - not to mention, that the camera even acted kinda "confused" when pressing the shutter release. When I mounted the lens back again properly (camera switched OFF), everything worked fine and I had no issues since - just knocking on wood

50-135 is truely a remarkable piece of glass - even usual MTF50 tests cannot really show the capabilities of it in the right proportion compared to others. That's why it is sad to see this kind of issues repeatedly being brought up. I have taken almost two thousand shots with it already and have only one problem with it - I just don't want to use my other lenses any more

05-04-2009, 10:15 AM   #24
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QuoteOriginally posted by asdf Quote
DA* 200 f/2.8:



FA* 200 f/2.8:


You should first ask yourself whether the optics of these lenses is good enough for you. The problem with older telephoto lenses is chromatic aberration--but, I guess, you can fix that in post-processing.
Is it just me or do the optical design of the DA* 200 and FA* 200 look identical?
05-04-2009, 01:46 PM   #25
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Well, I hope I don't jinx myself, but I'll just report that I've had 4 DA* lenses for over a year with no problems with any of them. Since people don't usually start a thread to say that all their equipment is working just fine, I thought I'd just chime in here.



I've yet to have a problem with any of my Pentax gear, save an occasional reluctance of the e-dials to change things on my K20D - and I'm not sure that it's not my fault.
05-04-2009, 02:03 PM   #26
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QuoteOriginally posted by rfortson Quote
Well, I hope I don't jinx myself, but I'll just report that I've had 4 DA* lenses for over a year with no problems with any of them. Since people don't usually start a thread to say that all their equipment is working just fine, I thought I'd just chime in here.



I've yet to have a problem with any of my Pentax gear, save an occasional reluctance of the e-dials to change things on my K20D - and I'm not sure that it's not my fault.
I've just sent in my K20D cause the rear e-dial started squeaking. It would still register, but didn't scroll smoothly. maybe you should look at sending it to get fixed.
05-04-2009, 02:14 PM   #27
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QuoteOriginally posted by nah Quote
I've just sent in my K20D cause the rear e-dial started squeaking. It would still register, but didn't scroll smoothly. maybe you should look at sending it to get fixed.
Interesting...my rear e-dial has dragged a bit ever since I bought it. I always assumed it was a slight misalignment of a weather seal, and it didn't bother me that bad. I don't think it is worth it for me to send it in for this small problem.
05-04-2009, 03:21 PM   #28
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QuoteOriginally posted by monochrome Quote
My best performing lenses in terms of solid feel, durability and accuracy are my Takumars. They are approximately 40 years old, and I see no reason they should ever stop working as long as they are periodically serviced - say once every 20 years.
Time was . . . .

QuoteOriginally posted by creampuff Quote
Sorry but talking about legacy lenses is a different context altogether to a modern AF lens, which is frankly quite a lot different construction wise.
Durability was expected . . . .

QuoteOriginally posted by monochrome Quote
Sorry to be so obtuse

My entire point is all the gimmicky, electronic motor stuff doesn't change the fact that glass transmits light - that hasn't changed at all.

I find it interesting that we want the durability of a brass and aluminum, lubricated, manually-operated device. Yet we expect that from a device that has nano-wires on circuit boards, motors with self-lubricating, enclosed bearings, machine solders rather than hand-assembly, etc. - and expect it to cost about the same in inflated dollars as a lens did in 1965. All the "improvements" have a cost - loss of durability.
But today we want everything for nothing (or less, anyway) . . . .

QuoteOriginally posted by asdf Quote
So expect people to write how they expect their manual focus lenses to outlast the SDM motor of their DA* lenses.
Already did - and I still believe if we ask for durability we have to either pay a lot more money or expect a much simpler lens. You can't afford both durability and modern features such as SDM autofocus for the same after-inflation money as a Takumar.
05-04-2009, 03:37 PM   #29
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QuoteOriginally posted by monochrome Quote
You can't afford both durability and modern features such as SDM autofocus for the same after-inflation money as a Takumar.
By the way - how are these over 10 years old Canon USM lenses are putting up?
05-04-2009, 05:08 PM   #30
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QuoteOriginally posted by tim71 Quote
By the way - how are these over 10 years old Canon USM lenses are putting up?
I don't know, but if they are as durable as ten years I bet they cost more in after-inflation money than a similar focal length Canon FL did in 1966
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