SDM Lenses


Link Posted 25/02/2012 - 09:39
Apologies if this has been answered before but I have a bit of a quandry.
Pentax SDM lenses keep getting mentioned on the forum for less than robust performance.
Is this true?
I guess what I am really asking is are they reliable or would my investment be better spent elsewhere.

I cannot afford to be in attendance at a clients wedding and be overly worried that my SDM lenses were going to
I admit to a certain level of paranoia after two Nikon F5's broke down within an hour of each other at a wedding
some years ago.
All opinions and advice gratefully appreciated.


Link Posted 25/02/2012 - 09:45
I have never had a problem with SDM lenses. I have the 17-70 and 60-250 and had the 50-135. Not a problem with any of them.

As with so many things you only hear when people do have a problem, not when they don't, and that creates a wrong impression imho.


Link Posted 25/02/2012 - 10:13
There are some good graphs on the US forum regarding SDM
reliability based on year purchased (started by Stefan).

Generally the primes seem quite good and the zooms have improved
over the years. The 17-70mm seems to have problems with something
like 50% still failing.
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff



Link Posted 25/02/2012 - 10:18
There may be some "good graphs" but, as always, how accurate they are will depend upon the source of the information. There are some very wild figures bandied about and I doubt very much that any lens from any manufacturer has a 50% failure rate.
Best regards, John


Link Posted 25/02/2012 - 10:33
I have a number of Pentax lenses with SDM... the 16-50; 50-135; 200 and 300. They are all beautiful lenses and I have not had an SDM failure yet (and they do get a decent amount of use). The only odd occasion where there has been any issue has been an issue with contacts rather than the SDM per se. From memory this has occurred twice in about 3 years and has been a ten second fix (cleaning the contacts) in each case.

Although this is just my experience. No system will have 100% reliability, and I am sure that those who are disappointed are much more likely to post on forums like this than (probably the vast majority) who are satisfied... (?)

Mat W

My Flickr: link


Link Posted 25/02/2012 - 11:07
Algernon wrote:
Generally the primes seem quite good and the zooms have improved
over the years. The 17-70mm seems to have problems with something
like 50% still failing.

Whoops misread the way they have drawn the graphs or possibly more results have been added since I last looked.

2010: 17-70mm 12 failed 25 OK so that's 12/37 = 32.4%

The results seem quite reliable because of the good results
from the primes. The DA*200mm f/2.8 only has 1 failure in
4 years out of 59 lenses.

The 16-50mm in 2009 shows 36 failed 43 OK = 36/79 = 45.6%

The 18-135mm has zero failures from 93 lenses....
It seems to me that the solution is simple
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Last Edited by Algernon on 25/02/2012 - 11:10


Link Posted 25/02/2012 - 11:40
Too small a sample Algi, and from a skewed sample as well. Skewed in that it was self-selecting.

Statistics have to be handled very carefully to be meaningful.
Best regards, John


Link Posted 25/02/2012 - 11:44
My 300 failed and was sent back for repair under warranty. Now works but not as fast as it used to!
Pentax K1-ii and MZ6
Pentax Lenses 28-80 F, 300 DA*, 80-200 F, 35 F2.4 AL, M50 F1.7, 28-105 DFA, 20 F4 SMC


Link Posted 25/02/2012 - 11:55
No SDM problems with 17-70 or 50-135
Too Old To Die Young


Link Posted 25/02/2012 - 13:58
No problems (other than wishing they would focus a bit quicker) with 16-50, 50-135, 60-250 and 55.




Link Posted 25/02/2012 - 15:50
My experience with SDM lenses has not been all positive, in fact they are the least reliable of all my lenses (which are mainly Pentax, with a couple of Sigmas, a Tamron and a Samyang). I have not experienced SDM failure but both my SDM lenses (17-70 and 16-50) sometimes fail to lock focus even in very average conditions. Frustrating as the IQ of both is excellent. Because of this I went for the Sigma 50-150 rather than the Pentax 50-135 when I wanted something longer.

They say lenses have a personality - the personality of my SDM's is that they fire when they feel so inclined - a wild exaggeration but you get the idea. They are good 95% of the time but the critical shot could be missed. I find switching from AF-S to AF-C helps.

Prompted by the posts above I have just given the contacts on both camera and lenses a good clean (again) to see if it will make any difference.
Regards, Philip
Last Edited by smudge on 25/02/2012 - 15:51


Link Posted 25/02/2012 - 16:02
Contacts build up a deposit of grease/dirt from the environment, so a periodic clean with a soft cloth is a good idea.
Best regards, John


Link Posted 25/02/2012 - 18:55
I have had 30 year old Pentax lenses (Manual Focus) that were still a pleasure to use, the focusing being so smooth.But I don't think my DA* 16-50 or DA* 50-135 will still be Autofocusing in 30 years time,I have my fingers crossed that I get 3 years trouble free, the 16-50 had to go back to Pentax twice in the first year because the SDM failed.
K5+Bigma+BushHawk Shoulderpod.
K5+16-50DA* + 10-17DA Fisheye + 50-135DA* + Sigma 70mm Macro + DA35 2.4..
Slik Pro 700DX tripod.


Link Posted 26/02/2012 - 00:20
Bill has a point about modern lenses being incredibly complex compared with manual focus ones. This applies to all marques of course, but I don't expect the lenses to survive as AF ones in quite the same way as lenses of 40 years ago have.

However, even after motors have worn out they may still manually focus well enough and hopefully wearing them out will take many years.
Best regards, John


Link Posted 26/02/2012 - 03:04
I have to confess to a personal policy of avoiding SDM lenses through a belief that simple is better. More complexity in engineering terms generally equates to higher failure rates and more expensive repairs, and I hate spending money on repairs that could otherwise be invested in more equipment! As an amateur I'm perfectly happy with the screw autofocus and there is a modern tendency to believe the advertising hype that new is best and old is obsolete.

Sure, if I was a pro sports or press photographer I might need SDM to keep up with the pack, but it's worth remembering too that photographers managed to take great action shots long before SDM was invented. Sometimes I think technology displaces craft.
Better equipment enhances my ability to display my shortcomings.
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