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01-21-2010, 02:18 AM   #31
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Well, this lens is a beauty, pity so many has problem with it.
It works wonderfully at weddings

01-21-2010, 02:17 PM   #32
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QuoteOriginally posted by Ash Quote
Perhaps an indication of earlier models being more prone to failure (if this is a true phenomenon)...
The first 2,000 (then from 10,000-12,000 and so forth) are implicated in the theory, but one can hazard to guess that the first 2,000 may be responsible for the large number of failures?

Seems a little far-fetched, but hey, better hypothesis than none, eh?...
Ash, want to make another hypothesis?

Gregoire came back and edited his post with:
"EDIT: actually, if 4th digit = 0, chance of a good copy is 90%, if it is =1, chance is 100% (!), if it is =2, chance is 77%."
01-22-2010, 03:26 PM   #33
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Pleas Sir, Please Sir ---can I hypothesise?

Not in Public Oggy!



I reckon there have been some SDM failures.

People who have paid quite a lot are justifiably miffed when this happens, and start ranting.

OTOH, there are a large number of SDM lenses out there which work very well indeed and produce exceptional images day in and day out, but no-one rants that lenses are working properly. Thus the problem gets blown out of all proportion.
01-22-2010, 04:41 PM   #34
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QuoteOriginally posted by Oggy Quote

OTOH, there are a large number of SDM lenses out there which work very well indeed and produce exceptional images day in and day out, but no-one rants that lenses are working properly. Thus the problem gets blown out of all proportion.
All the ones that have failed worked very well indeed... until they failed.

I see by your sig you have some incentive to be optimistic.

01-22-2010, 07:10 PM   #35
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QuoteOriginally posted by Oggy Quote
Pleas Sir, Please Sir ---can I hypothesise?

Not in Public Oggy!



I reckon there have been some SDM failures.

People who have paid quite a lot are justifiably miffed when this happens, and start ranting.

OTOH, there are a large number of SDM lenses out there which work very well indeed and produce exceptional images day in and day out, but no-one rants that lenses are working properly. Thus the problem gets blown out of all proportion.
I am so tired of that arguement.

I expect there are far more screw drive lenses in use then there are USM lenses. How often do you see a post about someones FA50 1.4 falling apart? I can think of one. Now consider how many people have and use that lens. I expect it is one of the most common lenses right after the DA 18-55 kit lens. BUT there are numerous users on this forum that have had issues with their DA* USM lens.

Also consider how many of the people with dud USM's are long time posters on this forum. Many are photographers that know their gear, and know how to use it. When I see a post from these users that their USM crapped out, I believe it.

If it is just "internet chatter" of failed USM, then sure I could see your point. But it is not. These are people that I know through this forum, and their lens has crapped out.

Imagine if we were colectivly part of a camera club, that actually met in person weekly. Say there are 100 people in the club with USM lenses, and say, 5 of the lenses were duds.

A 5% mortality rate on a top product is outragious. But hey, 95% are still working, so why worry right?

But, based on the data collected on this forum (https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/69791-superson...-safe-buy.html), the rate of USM failure might be as high as 25%. Now I understand with a pole such as this, the rate of reporting for the failed USM is higher then the rate of reporting for the good USM. So lets just say for arguements sake that the good lenses get reported 1/4 of the time. So then your failure rate becomes 8%. This is still way to high.

If we really wanted to, some one could look through all of the gear people have listed in their profiles, count all the USM lenses, then take the USM failures from that post, and come up with a new failure rate.

So if you have an 8% chance of failure in the first 4 years (USM was introduced in 2006?), then you have 92% chance that your lens will be fine.

If you have 3 lenses, then you chance of all three working after 4 years becomes about 78%. (0.92 x 0.92 x 0.92) wow, thats a 22% chance that at least one of your lenses will fail over 4 years.

If the data is correct and all of the forums USM users posted, then with a 25% failure rate, and if you own three lenses, then you have a 42% chance of all three lenses will be working after four years.

Maybe I've forgotten my statistics, and I'm sure someone will correct me, but these numbers don't make me want to buy one of these lenses.
01-23-2010, 05:45 AM   #36
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Oggy, you need to take a course in basic statistics, say, probability math and the Bayes' theorem. After that you can discuss the issue again, but until then it is fairly pointless.
01-23-2010, 06:31 AM   #37
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The problem is that we know there are significantly more kit lenses sold than (much more expensive) DA* lenses. Yet, we hear no issues with these lenses and we hear about many issues with the SDM on the DA * lenses. Obviously the internet does tend to magnify issues, but there is a real issue here and one that is only being addressed in secret (if it is being addressed at all) by Pentax/Hoya.
01-23-2010, 08:53 AM   #38
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One thing I don't get is how Pentax leapt headlong into SDM. Many with the 16-50's like the lens, but can't stand how you're forced to use SDM - always, perpetually, no-choice-in-the-matter - on cameras with SDM while the reliable, if noisy, screw drive is off limits.

Surely in the pro-grade, high-end lenses like the 16-50, wouldn't it be great to have the redundancy, especially if you're making a living off your camera?

Why not the following?

* Lens switched to AF, body switched to AF: SDM focusing.
*Lens switched to MF, body switched to AF: screw drive focusing.

This seems like one of those little things Pentax would do, a handy little feature that's not that hard to implement.

01-23-2010, 08:56 AM   #39
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Or just have a switch in settings to disable SDM and use screw-drive instead. It is a trivial firmware change, but it would be admitting that there is a problem with SDM and that is why they don't do it.
01-23-2010, 12:24 PM   #40
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QuoteOriginally posted by lithos Quote
One thing I don't get is how Pentax leapt headlong into SDM. Many with the 16-50's like the lens, but can't stand how you're forced to use SDM - always, perpetually, no-choice-in-the-matter - on cameras with SDM while the reliable, if noisy, screw drive is off limits.

Surely in the pro-grade, high-end lenses like the 16-50, wouldn't it be great to have the redundancy, especially if you're making a living off your camera?

Why not the following?

* Lens switched to AF, body switched to AF: SDM focusing.
*Lens switched to MF, body switched to AF: screw drive focusing.

This seems like one of those little things Pentax would do, a handy little feature that's not that hard to implement.
They would never do this because it is an admision that SDM is not as good as screw drive.

[sarcasm on]
The only reason you would switch from SDM to screw drive is due to SDM failure (we know this is not a problem), or screw drive is faster (no chance of that SDM is new how could it be slower?).
[/sarcasm off]

The ability to choose SDM or screwdrive, I am sure, is an easy firmware fix.

I expect it ha been discussed in their product development meetings. I am sure the engineer or technical rep has brought this up. For it to be nerfed in such a fashion smaks of marketing and management stratagy.

More great design ideas die at the boardroom then you could imagine.
01-23-2010, 12:41 PM   #41
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QuoteOriginally posted by KungPOW Quote
The ability to choose SDM or screwdrive, I am sure, is an easy firmware fix.
Yes, this is a verifiable fact. the k10d with original software would use the screwdrive to focus the 16-50 and 50-135. When Pentax released a firmware update, it focused using SDM. Screw drive was no longer possible.
01-23-2010, 01:18 PM   #42
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But this is only true on the lenses that have both screw drive and SDM capability. All the people who have purchased the DA*55 and DA 17-70 would still be hosed.
01-23-2010, 04:52 PM   #43
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QuoteOriginally posted by KungPOW Quote
...But, based on the data collected on this forum (https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/69791-superson...-safe-buy.html), the rate of USM failure might be as high as 25%. Now I understand with a pole such as this, the rate of reporting for the failed USM is higher then the rate of reporting for the good USM. So lets just say for arguements sake that the good lenses get reported 1/4 of the time. So then your failure rate becomes 8%. This is still way to high....

Looking at that "survey" -

18.6% are going on hearsay so absent themselves from any rigourous analysis.

People who have more than one SDM lens only get one vote. This makes the sample unrepresentitive.

Most of my maths is to do with real time mathematical modelling for simulators, and I have little to do with statistics. The one thing I did enjoy about stats though was that with one barely visible tweak, you could get them to show exaxctly what you want.


That aside, here's another thing - on other Pentax forums, this "issue" hardly gets a mention.
01-23-2010, 07:30 PM   #44
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QuoteOriginally posted by Oggy Quote
That aside, here's another thing - on other Pentax forums, this "issue" hardly gets a mention.


I'm not sure what the definition of "hardly" is in the UK, but it sure doesn't mean the same thing to me that you think it means. These are just a few of the threads of SDM failure complaints on DPreview alone! (Credit to Russel-Evans) The list hasn't even been updated in over a month. So I guess if the definition of "hardly" in the UK means "persistently," or "constantly," or "continuously," or "without end," then I would have to agree with you:

QuoteOriginally posted by Russell-Evans Quote
I couldn't find that thread, but I did find these.

Sophie Wilson
Help! Dead DA* 50-135 SDM or dead K10D???: Pentax SLR Talk Forum: Digital Photography Review
HonourableTyr
Perfect DA*16-50 Not so perfect anymore :'(: Pentax SLR Talk Forum: Digital Photography Review
robt61x49
Problem w/ DA*50-135: Pentax SLR Talk Forum: Digital Photography Review
Rupert60
My DA*50-135 is Dead!: Pentax SLR Talk Forum: Digital Photography Review
paul_do
K20D+DA* 50-135mm is amazing: Pentax SLR Talk Forum: Digital Photography Review
Larry Paris
DA*300 Auto focus stopped working - Help!: Pentax SLR Talk Forum: Digital Photography Review
janneman02
SDM issue????: Pentax SLR Talk Forum: Digital Photography Review
Dale108
DA* 50-135 SDM Failure: Pentax SLR Talk Forum: Digital Photography Review
Eric C in OK
Re: SDM issue????: Pentax SLR Talk Forum: Digital Photography Review
LKeithR
Another Failing 50-135: Pentax SLR Talk Forum: Digital Photography Review
psu28k
50-135 SDM woes: Pentax SLR Talk Forum: Digital Photography Review
Reg Quiring
DA* 50-135 SDM Failed- Other Canucks?: Pentax SLR Talk Forum: Digital Photography Review
rogerstpierre
SDM Problems...: Pentax SLR Talk Forum: Digital Photography Review
inferno10
Help Ned! Replacement 16-50 has to go back after just receiving it!: Pentax SLR Talk Forum: Digital Photography Review
faither
Another Dead SDM in My DA* 50-135: Pentax SLR Talk Forum: Digital Photography Review
Jim King
Finally experienced an SDM failure...: Pentax SLR Talk Forum: Digital Photography Review
Neil Morgan
yes - 16-50 (sometimes) , 50-135 - no: Pentax SLR Talk Forum: Digital Photography Review
dick eduard
16-50 sometimes-; 50-135 - no; 60-250 no: Pentax SLR Talk Forum: Digital Photography Review
shane gerrish
16-50 yes: Pentax SLR Talk Forum: Digital Photography Review
Zevon
16-50 Yes 60-250 No: Pentax SLR Talk Forum: Digital Photography Review
mnovikov
50-135 no, 16-50 yes (fixed) n/t: Pentax SLR Talk Forum: Digital Photography Review
hanssont
200-yes 300-no 60-250 no 16-50 no 50-135 no 55 no: Pentax SLR Talk Forum: Digital Photography Review
Cideway
16-50 (2yrs) No, 50-135 (1.5yrs) yes, 60-250 (3mths) No: Pentax SLR Talk Forum: Digital Photography Review
ropen
0.5 out of 4: Pentax SLR Talk Forum: Digital Photography Review
HotJapaneseCamera
Yes, 16-50 (2nd ex.) No, 50-135: Pentax SLR Talk Forum: Digital Photography Review
Mike V99
16-50 YES, 50-135 No (as in Not Yet): Pentax SLR Talk Forum: Digital Photography Review
sinus007
16-50 - yes, 50-135 - no [nt]: Pentax SLR Talk Forum: Digital Photography Review
Joseph Tainter
Yes--16-50: Pentax SLR Talk Forum: Digital Photography Review
JoeLim
Yes, 16-50 (9 months) & 50-135 (6 months). 300 (3 months) No: Pentax SLR Talk Forum: Digital Photography Review
PentaxPoke
Yes 16-50: Pentax SLR Talk Forum: Digital Photography Review
Paul_E
16-50 x 2, no SDM failure; 50-135, yes; DA*300, no failure.: Pentax SLR Talk Forum: Digital Photography Review
Lance
Re: My 17-70 SDM Died :( ... has come back to life !!: Pentax SLR Talk Forum: Digital Photography Review
gerard boulanger
Got a repair estimate for my 3 faulty SDM lenses ....: Pentax SLR Talk Forum: Digital Photography Review
flash1100
Took the DA17-70 in today...: Pentax SLR Talk Forum: Digital Photography Review
AndresEE
50-135: 2 x YES: Pentax SLR Talk Forum: Digital Photography Review
A Schamber
One... out of two.: Pentax SLR Talk Forum: Digital Photography Review
DarylK
Second 50-135 failed: Pentax SLR Talk Forum: Digital Photography Review
AlbertSiegel
Re: Second 50-135 failed: Pentax SLR Talk Forum: Digital Photography Review
John Shakespeare
Mine died also, but within warranty...: Pentax SLR Talk Forum: Digital Photography Review
RobertBarnett
Re: DA*16-50 problem: Pentax SLR Talk Forum: Digital Photography Review
WildSammy
Re: DA*16-50 problem too!: Pentax SLR Talk Forum: Digital Photography Review
picsbydan
Re: 50-135 SDM woes: Pentax SLR Talk Forum: Digital Photography Review
Paul_E
Re: 50-135 SDM woes: Pentax SLR Talk Forum: Digital Photography Review
roxalo
Re: How much was the fee if you don't mind me asking?: Pentax SLR Talk Forum: Digital Photography Review
Anilla
DA 16-50 SDM problems: Pentax SLR Talk Forum: Digital Photography Review
ZorKa
My lens has the same problem...: Pentax SLR Talk Forum: Digital Photography Review
magicone
New DA*50-135 won't focus w/K10 or K20: Pentax SLR Talk Forum: Digital Photography Review
Pakhead
Re: More experience with SDM problems: Pentax SLR Talk Forum: Digital Photography Review
FranckB
17-70: Pentax SLR Talk Forum: Digital Photography Review
Moosemilk
8 problematic lenses reported in this thread so far.: Pentax SLR Talk Forum: Digital Photography Review


Thank you
Russell

Last edited by PentaxPoke; 01-23-2010 at 07:39 PM.
01-23-2010, 09:03 PM   #45
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OP is not trying to sell his copy on ebay or anything like that, is he? Just a thought. You know, when you get to live over 70 years you become cynical.
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