SDM issues? A straw poll.

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yelvertoft

Link Posted 30/09/2009 - 12:13
had 50-135 for nearly 4 months now, not long I know, but no problems so far, it's had some heavy use in that time. I love this lens.

thoughton

Link Posted 30/09/2009 - 14:08
You'd better subtract one of the 'No' answers as I don't have any SDM lenses, but I voted No just so I could see the poll results!
Tim
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!

hefty1

Link Posted 30/09/2009 - 14:15
I haven't voted 'cos I don't own an SDM lens - anyone who can see the results care to give an update on how they're going?
Joining the Q

thoughton

Link Posted 30/09/2009 - 14:21
39 No (38 minus mine) and 8 Yes so far!
Tim
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!
Last Edited by thoughton on 30/09/2009 - 14:21

hefty1

Link Posted 30/09/2009 - 14:24
Cheers
Joining the Q

RichardDay

Link Posted 30/09/2009 - 17:05
NeilP wrote:
Sigma 150-500mm SDM lens 4 months no problems (I hope this counts as its advertised as HSM/SDM)

Sorry, will have to discount this as it's only for Pentax SDM lenses.
Best regards
Richard Day

Profile - link - (click on About for equipment profile) - My Flickr site - link

RichardDay

Link Posted 30/09/2009 - 17:11
So Far.

5 definite complaints (including the "maybe"!) detailed with 8 "yes" votes. There is some anonymous posting going on, so I shall discount 3 of the 8.

Of the "No" votes, many who have detailed a response have several lenses, a total of 63 lenses with no failures from 25 posters from 41 who have said "No" so there have been 16 anonymous "No problem" posters. If I take these 16 posters as owning 1 lens rather than the average of 2.5 lenses, that gives 79 "no" votes against 5 "yes".

Unfortunately there is no way of having several groups of tick boxes to fine tune the results more accurately.

So I would guess that the failure rate seems to be around 6% so far, mainly it seems with the first two designs, 16-50 & 50-135, though we do have a suspect 60-250.

Let's see how many more responses we get before we call it quits.
Best regards
Richard Day

Profile - link - (click on About for equipment profile) - My Flickr site - link
Last Edited by RichardDay on 30/09/2009 - 17:26

Thordell

Link Posted 30/09/2009 - 19:45
Only had mine a few months and it is not been used much, however it is silky smooth and I have had no problems.

EDIT: sorry it is a 60-250
Jackie H
K7, K20D, istDS, Optio SV, ME
Most used glass
50mm f1.4, 60-250mm, 28-80mm,
Sigma 105mm 2.8 Macro & Bertha 50-500
Last Edited by Thordell on 30/09/2009 - 19:46

bramela

Link Posted 01/10/2009 - 01:59
Have owned a 50-135 for approx 15 months... No problems, very happy with it.

jamesm007

Link Posted 01/10/2009 - 06:47
Hello, Richard nice site! Nice poll! One suggestion to make it IMO a bit more accurate. No one disputes the DA*300mm, DA*200mm or DA*60-250mm are for the most problem free. The main complaints are toward the DA*50-135mm and DA*16-50mm. I would aggregate all of those lens for you percentage as this will more accurately reflect what we already know, and what we don't know; or in other words get your figure closer to the actual failure rate of those two lens.

Also if you consider any QC problem, SDM or not, say slow AF, as we are not able to separate issues with the facts we have that may have a root cause in the SDM system, or at least for the owner it does not matter as it may still be poor QC there is no way to separate the two. the percentage of DA*16-50mm and DA*50-135mm no matter how you want to add it, on your own poll, is kinda high. I won't say the exact figures as this is your show and I may have added wrong, I for sure am not perfect at 2:00am. Just my two cents

Shaky

Link Posted 01/10/2009 - 07:43
jamesm007 wrote:
The main complaints are toward the DA*50-135mm and DA*16-50mm. I would aggregate all of those lens for you percentage as this will more accurately reflect what we already know, and what we don't know; or in other words get your figure closer to the actual failure rate of those two lens.

The objective of this exercise is worthy but neither the original approach nor the one you outline are in any sense rigorous since both fail to take time into account.

If you consider any mechanical product, the greater the age the greater the chances of a fault developing. However, here a faultless lens (in terms of SDM) is equally weighted whether it is a 2 weeks old or two years. As such Richard's apparent inference that problems with SDM have been fixed in the 60-250mm is simply unsustainable; it could just as easily be due to the fact that the model has only recently been released.

If time owned and time to fault were provided you could plot the data in a scatter diagram, and try to determine whether clusters are forming in terms of time to failure, either on a lens by lens basis or in aggregate for all models.

Separately, I must say that the requirement that faults must be detailed while problem free instances just get to cast a vote are a complete no-no from a survey design perspective. You simply can not make the casting of one type of vote easier than another, especially when the more onerous is the case you are explicitly attempting to disprove. I think this is illustrated in Richard's comment that average ownership is 2.5 lenses/respondent which I don't believe passes the smell test.

However, if the survey were repeated on the basis that qualitative data is required from all respondents (eg "I have had lenses xyz for abc months respectively and no faults have developed") that issue would be eliminated.

Lance B

Link Posted 01/10/2009 - 08:59
Shaky wrote:
jamesm007 wrote:
The main complaints are toward the DA*50-135mm and DA*16-50mm. I would aggregate all of those lens for you percentage as this will more accurately reflect what we already know, and what we don't know; or in other words get your figure closer to the actual failure rate of those two lens.

The objective of this exercise is worthy but neither the original approach nor the one you outline are in any sense rigorous since both fail to take time into account.

If you consider any mechanical product, the greater the age the greater the chances of a fault developing. However, here a faultless lens (in terms of SDM) is equally weighted whether it is a 2 weeks old or two years. As such Richard's apparent inference that problems with SDM have been fixed in the 60-250mm is simply unsustainable; it could just as easily be due to the fact that the model has only recently been released.

If time owned and time to fault were provided you could plot the data in a scatter diagram, and try to determine whether clusters are forming in terms of time to failure, either on a lens by lens basis or in aggregate for all models.

Separately, I must say that the requirement that faults must be detailed while problem free instances just get to cast a vote are a complete no-no from a survey design perspective. You simply can not make the casting of one type of vote easier than another, especially when the more onerous is the case you are explicitly attempting to disprove. I think this is illustrated in Richard's comment that average ownership is 2.5 lenses/respondent which I don't believe passes the smell test.

However, if the survey were repeated on the basis that qualitative data is required from all respondents (eg "I have had lenses xyz for abc months respectively and no faults have developed") that issue would be eliminated.

But even then, I think you would need to further check the number of shots taken with the lens as how long you've had it could just mean that the lens sat in the cupboard for 6 months and not used.
Cameras:K-7/K20D/*ist D/K10D
Lenses:DA14 f2.8, A16 f2.8, FA20 f2.8, FA31 f1.8, DA35 f2.8 macro, FA43 f1.9, FA50 f1.4, A50 f1.4, A50 f1.2, FA50 f2.8 macro, DA*55 f1.4, FA77 f1.8, DFA100 f2.8 macro, A100 f2.8, DA*300 f4, FA*300 f4.5, DA10-17 FE, DA12-24 f4, DA*16-50 f2.8, DA17-70 f4, FA*28-70 f2.8, DA*50-135 f2.8, DA*60-250 f4, FA*80-200 f2.8.
Flashes:AF540FGZ, AF360FGZ

George Lazarette

Link Posted 01/10/2009 - 09:06
The fact is that all such surveys are flawed, and really not worth a great deal. To counter Shaky's point about it being harder to vote for a faulty lens is the fact that people with faulty lenses are much more likely to participate in such a poll. But how do you know which factor had more influence?

Generally, though, Shaky is right. I don't tend to vote in polls because they are so flawed. They're like referendums - fine for totally unimportant matters like choosing a national anthem, but quite useless for anything else.

G
Keywords: Charming, polite, and generally agreeable.

FredEriksson

Link Posted 01/10/2009 - 09:33
I have the 50-135 since 2 months and I voted no. However, on rare occasions the lens has not been able to find focus the AF never settles and just moves backwards and forwards a small distance. It has only happened 2-3 times and can be fixed by refocussing on something closer and then just try again. I wouldn't call it an SDM failure. Still, if this is a sign of something worse to come maybe I'll change my opinion. All in all, it's a lovely lens and I'm very happy with IQ it generates.

Cheers,
/Fred

Anvh

Link Posted 01/10/2009 - 09:40
Fred that is an auto focus failure not a SDM one, SDM is simply the motor that drives the focus system of the lens, nothing more nothing less.

As for your problem, it's quite normal and it's called haunting.
The AF sensor needs contrast to see if the focus is "sharp" or not and it does not like low light since contrast will drop as well and it reads the light that reflects from the subject.
It simply is not able to see sometimes so it will miss the focus.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
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