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06-29-2012, 11:35 AM   #2896
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I feel like i'm running in circles.

- Okay SDM is just an ultrasonic motor used in a lot of lenses successfully and without any reliability issues, cannon don't have a motor in the body for a years now so please stop saying the ultrasonics motors aren't reliable because that isnt the case.
- speed really depends on the lens design and not so much the motor

Sure the reliability of the DA*16-50 and DA*50-135 is not good but can you proof to me it's the SDM that's causing the problem?
And to go a bit further explain why the DA*300 has so good as no failures at all?

06-29-2012, 11:36 AM   #2897
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QuoteOriginally posted by Mareket Quote

Also, dear god I want a Limited.
I'm selling off a bunch of stuff right now to fund a 21 a da50 and an fa77 or da70 so i sympathise (the worse my eyes get the harder manual focus gets so I'm only keeping my Taks ultimately, and will p/u a Fuji AF Rangefinder for my medium format fooling around)
06-29-2012, 11:43 AM   #2898
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And more limited lenses are coming...
06-29-2012, 11:45 AM   #2899
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As someone who loves shooting landscapes... I would love MF over FF since most of my shooting is on a tripod anyways.. But the cost scale is out to lunch even with th 645D.. Hence why the D800 will do SOO well.. the high resolution helps borderline into MF territory, yet retains the versatility and advantages of FF over APS-C.. as for the crop factor.. it's a non-issue on a D800 since you can keep high resolution shots even after cropping.. or get a DX lens and still be around 20MP (not sure since I don't have any DX glass.. never cared to much about that spec).

06-29-2012, 06:07 PM   #2900
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QuoteOriginally posted by Anvh Quote
- Okay SDM is just an ultrasonic motor used in a lot of lenses successfully and without any reliability issues, cannon don't have a motor in the body for a years now so please stop saying the ultrasonics motors aren't reliable because that isnt the case.
You cannot compare the very robust and fast ring motors (used by Sigma or Canon in their better lenses) with the micro-motor SDM solution Pentax is using. Both types of motors use ultra-sonic frequencies to operate but that's where the similarities stop.

There is no doubt that Pentax SDM has had significant reliability issues and thus have nurtured the argument that if you make a lens more complicated then you are also increasing the chances of having it fail.

I'd rather have no image stabilisation or focusing motor or whatever technology in my lenses. Even if you are using the more reliable and quicker ring-motor technology, no matter how reliable any additional technology is on average, it still increase the chances of devaluing a lens overnight.

If someone needs silent focusing, fine. If someone does not, they shouldn't be forced to argue why they'd rather not spend more money on SDM repairs.

QuoteOriginally posted by Anvh Quote
Sure the reliability of the DA*16-50 and DA*50-135 is not good but can you proof to me it's the SDM that's causing the problem?
There are a number of threads that provide insights into why these zooms fail so often. Apparently, it is a combination of a design weakness potentially compounded by sloppy assembly that allows the micro-motor to bind up over time.

Nothing points to quick-shift or the combination of SDM and screw-drive AF as the source of the problem. The source always appears to be a micro-motor becoming jammed.

Other lens models, such as the DA* 300 you mention may not have that particular design weakness, there may be less weight to move around hence causing less strain on the drive assembly, etc.

In any event, someone with an SDM lens that does not focus anymore probably could care less if the root cause is a broken micro-motor, a jam that is the result of a design flaw, a jam that is the result of a sub-par assembly, or whatever. An equivalent screw-drive lens would still be focusing.

QuoteOriginally posted by Anvh Quote
- speed really depends on the lens design and not so much the motor
The AF speed increases achieved by using faster in-body AF motors in recent Pentax DSLRs suggest that both lens design and motor speed have a significant role to play.

Last edited by Class A; 06-29-2012 at 06:15 PM.
06-29-2012, 06:47 PM   #2901
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Very sure that Canon use the same type of motor in some of their lenses, i remember some mention the newer Sigma lenses also using the same type of motor, not sure about nikon but i doubt they will use the ring type in their budget lenses as well, so my point still stands.


Well you either add in mechanical competent for the screw-drive motor or electrical wires and a motor, either way you interchange components... unless you're called pentax of course and put 3 different focus systems in a lens....


Of course it doesnt matter to him where the problem lies when his lens stop working but and that's not the point. It's just that the fault is always lay with the SDM motor without any prove it actually is the motor that cause the failure and im saying that's not correct or fair.
The lens is faulty but not per se the SDM motor.


Sure a faster motor helps, but only so much and surely not significant, if the lens group only need to move a little like with the DA18-135 which have a specially rear focusing group for faster focusing you know you've a fast lens in your hands.


ps. looked it up the motor canon calls micro usm is the same as the SDM.
The sigma 17-50 and 18-125 use the micro motor type and not the ring, not sure about other lenses but it seems likely.

Last edited by Anvh; 06-29-2012 at 07:02 PM.
06-29-2012, 09:52 PM   #2902
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QuoteOriginally posted by Anvh Quote
Very sure that Canon use the same type of motor in some of their lenses, i remember some mention the newer Sigma lenses also using the same type of motor, ...
That's why I wrote "better lenses".
Both Sigma and Canon use micro-motors (as opposed to ring motors) in some (typically cheaper) lenses.

QuoteOriginally posted by Anvh Quote
...so my point still stands.
I'm not sure what point you are trying to make.

Are ring motors reliable? Yes.

Can micro-motors be employed so that they are reliable? Yes.


But:

Can micro-motors be employed so that the whole AF system becomes unreliable? Yes (the Pentax SDM zooms provide ample proof).

Is a motor-less lens more reliable than one with a motor? Yes (I don't have access to respective failure rates, but I'm rather sure that the statistics will give the nod to srew-drive lenses rather decisively).


While ring-type motors are very reliable, there are rare reports of failures. I do not know whether micro-motors are less reliable in general, but surely we know examples where they cause a lot of failure reports.

QuoteOriginally posted by Anvh Quote
Well you either add in mechanical competent for the screw-drive motor or electrical wires and a motor...
Ever heard of a screw-drive gear train breaking?
Maybe there are isolated cases but they must be hugely outnumbered by the cases where a motor (whatever type) packs up.


QuoteOriginally posted by Anvh Quote
It's just that the fault is always lay with the SDM motor without any prove it actually is the motor that cause the failure and im saying that's not correct or fair.
I'd say it isn't fair to charge a lot of money for an expensive lens and than repeatedly charge some more money for repeated repairs because there is something wrong with your SDM design.

And again, it does not matter whether the SDM motor itself or something else in the SDM mechanism causes the lens to fail. The main point is that a screw-drive mechanism would still work.

I do not believe anyone is arguing that the SDM motor itself is the problem and hence one must avoid using one at all times. People are just annoyed by the SDM mechanism as a whole crapping out. There is no value or consolation for them in knowing that the SDM motor itself may have continued to work in another lens with less weight to move around, or whatever.
06-30-2012, 12:10 AM - 1 Like   #2903
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QuoteOriginally posted by Anvh Quote
I feel like i'm running in circles.
It looks like you all are. If you're desperate for silent focusing, do it manually - like we used to before A/F came along. Meanwhile please leave the rest of us to enjoy our reliable screw drives.

06-30-2012, 12:56 AM   #2904
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I remember, when Pentax had only screw drive AF, all the cries about how their AF is antiquated, noisy & slow, how everyone else had USM which was so much better blah blah blah. Are you saying we should return to those glorious days?
You'd be surprised how many would like and pay for a reliable, fast "SDM" coupled with a good AF system. Of course, your solution is to tell them "f*ck off"... but I think Pentax has a different idea.
By the way, how reliable were the first USM lenses? I doubt they got it right from day one; and guess what, neither did Pentax.
06-30-2012, 03:58 AM   #2905
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To me its also an issue of elegance. Would you rather have one engine in a car, or one engine on each wheel? Where you would have to pay for a new engine every time you exchange the tire?
And as said, the main problems with Pentax AF isn't even the screw drive. Its the lens design and AF system. But the motor lenses have one added potential problem and always an added cost. I think the only lenses that should have their own motor are ones that cannot be reliably focused using the in-camera motor (if they need more power, for example). To me it also seems more practical from the point of view of upgrades. If Pentax improves the screw-drive, you just buy a new body and all your lenses will now 'run better.' With lenses that have motors you need to do maintenance and buy a new variant when yours becomes outdated or obsolete. And motors will definitely fall apart over time, this isn't even up for debate. It might take years, even a decade, but it will happen. Not to mention planned planned obsolescence (and I'm not saying Pentax is doing this)
Also, if SDM is a feature, it would be great if the system would also allow it to be turned off and become a screw-drive lens. I think this has already been suggested numerous times.
06-30-2012, 04:42 AM   #2906
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QuoteOriginally posted by Class A Quote
I do not believe anyone is arguing that the SDM motor itself is the problem and hence one must avoid using one at all times. People are just annoyed by the SDM mechanism as a whole crapping out. There is no value or consolation for them in knowing that the SDM motor itself may have continued to work in another lens with less weight to move around, or whatever.
There are a lot off people saying out right that they don't trust the SDM motor at all because look at how many failed DA*16-50 there are. I understand where they coming from but it's just unreasonable to also put the DA* primes under the same group and that's the only thing i'm saying.

You don't seem to be against that point so what are you arguing about? XD
06-30-2012, 04:54 AM   #2907
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QuoteOriginally posted by Na Horuk Quote
To me its also an issue of elegance. Would you rather have one engine in a car, or one engine on each wheel? Where you would have to pay for a new engine every time you exchange the tire?
And as said, the main problems with Pentax AF isn't even the screw drive. Its the lens design and AF system. But the motor lenses have one added potential problem and always an added cost. I think the only lenses that should have their own motor are ones that cannot be reliably focused using the in-camera motor (if they need more power, for example). To me it also seems more practical from the point of view of upgrades. If Pentax improves the screw-drive, you just buy a new body and all your lenses will now 'run better.' With lenses that have motors you need to do maintenance and buy a new variant when yours becomes outdated or obsolete. And motors will definitely fall apart over time, this isn't even up for debate. It might take years, even a decade, but it will happen. Not to mention planned planned obsolescence (and I'm not saying Pentax is doing this)
Also, if SDM is a feature, it would be great if the system would also allow it to be turned off and become a screw-drive lens. I think this has already been suggested numerous times.
Your comparison is silly and you know that.
The SDM motor and the DC motor are placed near the mount so if you remove the cover there you've acces to the motor, that are 4 screws i believe.
The motor in the lens has one clear advantage, you can finetune the motor specifically to the lens.
About upgrade to the screw-drive, i've actually not heard off any yet but the upgrade to the AF system also benefited the SDM lenses so far.

About your last sentence as far as i know Pentax isnt doing that because if the SDM fails it often fails for a reason so if you switch to screw-drive you dont know what will happen. If after 2 months the whole AF system in the lens is jammed and also break the in camera motor...
Anyway they already have said not to make SDM/DC lenses with screw-drive anymore so that makes the option somewhat obsolete.
06-30-2012, 07:45 AM   #2908
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QuoteOriginally posted by Anvh Quote
Your comparison is silly and you know that.
Not silly at all, AFAIC.
The way you are arguing, it appears you should be switching to Canikon because they have lens-based image stabilization. They can "fine-tune" the stabilisation to the lens, have optimal motors, etc.

If you see the advantages of a body-based stabilisation approach, however, you should also see the advantages of a body-based AF approach.

QuoteOriginally posted by Anvh Quote
The SDM motor and the DC motor are placed near the mount so if you remove the cover there you've acces to the motor, that are 4 screws i believe.
And then you marvel at your broken SDM mechanism? Sometimes the DIY method described in this forum may help, but other times the SDM motor just needs replacing (ask those who had this item on their service bills).

QuoteOriginally posted by Anvh Quote
The motor in the lens has one clear advantage, you can finetune the motor specifically to the lens.
Or you just fine-tune the screw-drive gears specifically to the lens. Where is the difference? One can even imagine that the camera operates the in-body motor differently based on the lens recognised. I don't think that's ever necessary, but it would be a possibility.

QuoteOriginally posted by Anvh Quote
About your last sentence as far as i know Pentax isnt doing that because if the SDM fails it often fails for a reason so if you switch to screw-drive you dont know what will happen. If after 2 months the whole AF system in the lens is jammed and also break the in camera motor...
How did you learn about this alleged motivation?

To the best of my knowledge, no one has ever posted any inside knowledge as to why the many pleas to allow engaging screw-drive AF as an alternative to SDM (in the case of SDM failures, but also when you want to use certain teleconverters) has fallen on deaf ears.

The main hypothesis is that Pentax appears to be avoiding to implicitly acknowledge the abnormal frequency of SDM zoom failures.

Have you read the threads about SDM failures? I'm not aware of any case were the reason was any other than a jammed SDM motor. The screw-drive mechanism is decoupled from the SDM train, so it will drive the lens even if the SDM part is jammed.

If anything else were wrong, the camera AF motor would most likely deal with it, unless you forced the matter.

QuoteOriginally posted by Anvh Quote
Anyway they already have said not to make SDM/DC lenses with screw-drive anymore so that makes the option somewhat obsolete.
The many users who had their dual AF mode SDM lenses serviced (sometimes more than once) because of a jammed SDM motor and who would have happily avoided the service bill by engaging the screw-drive alternative disagree with you.

I believe it would help used market values for SDM zooms, if people had the chance to engage screw-drive AF, rather than being forced to pay a substantial bill in order to gain AF back.
06-30-2012, 10:29 AM   #2909
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QuoteOriginally posted by Class A Quote
Not silly at all, AFAIC.
The way you are arguing, it appears you should be switching to Canikon because they have lens-based image stabilization. They can "fine-tune" the stabilisation to the lens, have optimal motors, etc.
That has nothing to do with the comparison, we are talking about tires and motors driven them so when the tire is worn out you also replace the engine... so aplying that to the lens it means when the lens is worn out you also replace the focusing motor.... when the lens wears out??

QuoteQuote:
And then you marvel at your broken SDM mechanism? Sometimes the DIY method described in this forum may help, but other times the SDM motor just needs replacing (ask those who had this item on their service bills).
That was not the point, the point is the SDM is made to be serviceable, so if that's the problem they can replace it without that you need to buy a complete new lens, something that is actually suggested.

QuoteQuote:
Or you just fine-tune the screw-drive gears specifically to the lens. Where is the difference? One can even imagine that the camera operates the in-body motor differently based on the lens recognised. I don't think that's ever necessary, but it would be a possibility.
But who says that the motor in the Kr is the same as in the K30 for example? so you cant fine tune a lens to a camera.


QuoteQuote:
How did you learn about this alleged motivation?

To the best of my knowledge, no one has ever posted any inside knowledge as to why the many pleas to allow engaging screw-drive AF as an alternative to SDM (in the case of SDM failures, but also when you want to use certain teleconverters) has fallen on deaf ears.

The main hypothesis is that Pentax appears to be avoiding to implicitly acknowledge the abnormal frequency of SDM zoom failures.

Have you read the threads about SDM failures? I'm not aware of any case were the reason was any other than a jammed SDM motor. The screw-drive mechanism is decoupled from the SDM train, so it will drive the lens even if the SDM part is jammed.

If anything else were wrong, the camera AF motor would most likely deal with it, unless you forced the matter.

The many users who had their dual AF mode SDM lenses serviced (sometimes more than once) because of a jammed SDM motor and who would have happily avoided the service bill by engaging the screw-drive alternative disagree with you.

I believe it would help used market values for SDM zooms, if people had the chance to engage screw-drive AF, rather than being forced to pay a substantial bill in order to gain AF back.
An message from pentax came out with a failed SDM in a DA*16-50, the reason for that was because of a misalignment of a shaft, which occurred according to pentax during transport (yeah right)
Anyway just think about the many components needed for the AF inside the DA*16-50 with all the clutches and gears so it might quite possibly be true, maybe not in all cases.

So no Pentax wont give you an option for this, maybe they might put it i the debug/service menu but then if something goes wrong it's all at your own risk.
07-05-2012, 11:27 AM   #2910
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QuoteOriginally posted by Class A Quote

I'd rather have no image stabilisation or focusing motor or whatever technology in my lenses. Even if you are using the more reliable and quicker ring-motor technology, no matter how reliable any additional technology is on average, it still increase the chances of devaluing a lens overnight.
Well, I have shot brand C for about 3.5 years and have spent plenty of time with Canon owners and on Canon forums, and while there is no shortage of issues with Canon gear overall I honestly have not ONCE read about IS or AF failing on a lens. Not saying it doesn't happen, but it appears very, very unusual. So while it might "increase the chances of devaluing a lens overnight" it is by such a small margin that it isn't worth worrying about.

Personally I think in-body IS is great when using live view or an EVF. When using an OVF and with very long lenses I would rather have in-lens IS.
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