SDM Lens Failure

bc_the_path · 12-21-2009, 11:39 AM

My 50-135mm has just been fixed. The price was €223 (plus shipping charges).

It starts focusing after a moment or two even with a fully charged battery on a K20D.
The focusing is not fast by any standard and the SDM just fails to provide any confidence!
It is a difficult to describe feeling, I know.
Perhaps one can understand that more easily, if we talk about testing a car; sometimes you just "feel" that the car is not for you...

The lens is not good for manual focusing, either. The whole travel is about 90 degrees and there is no quick-shift.

I am still trying hard to love it but...

One thing is certain, though: If it fails again soon, I will not be surprised!!!
Call me biased!

----
ADDED:
A note on the poll statistics at the moment:
The percentage of 16-50mm lenses with an SDM failure is 26% (12 of 45).
The percentage of 50-135mm lenses with an SDM failure is 16% (10 of 63).
The display is probably based on another count so the percentages look different there (and they do not add up to 100%).

Last edited by bc_the_path; 01-03-2010 at 01:00 PM.

**Canada_Rockies** · 12-21-2009, 11:43 AM

Originally posted by bc_the_path

My 50-135mm has just been fixed. The price was €223 (plus shipping charges).

It starts focusing after a moment or two even with a fully charged battery on a K20D.
The focusing is not fast by any standard and the SDM just fails to provide any confidence!
It is a difficult to describe feeling, I know.
Perhaps one can understand that more easily, if we talk about testing a car; sometimes you just "feel" that the car is not for you...

The lens is not good for manual focusing, either. The whole travel is about 90 degrees and there is no quick-shift.

The lens does in fact have quick shift, as do all DA* lenses.

Quote:

I am still trying hard to love it but...

One thing is certain, though: If it fails again soon, I will not be surprised!!!
Call me biased!

bc_the_path · 12-21-2009, 12:09 PM

Canada Rockies:
>The lens does in fact have quick shift, as do all DA* lenses.

Of course it has!
I think I was subconsciously trying to find more excuses for not using this lens

Bart · 12-21-2009, 12:15 PM

Originally posted by Ash

Bart, under what conditions did your old 16-50 not lock focus?

Originally posted by Russell-Evans

...
I looked through Bart's posts and I think this is the one he was talking about:
Edit: I see you are talking about the issue with the returned "fixed" lens after it had been in for service as noted in this post.
...

Sorry for the late response - different time zones.
Russel is correct. that is what I was referring to.
And to be clear, I haven't had this problem with the new copy (yet?)

Originally posted by Canada_Rockies

I wonder if it is due to the difficulty of focusing ultra wide lenses in general? Ihave not had too much difficulty with mine, but occasionally, I have to point it at something with some contrast, particularly at the wider angles, 16 - 18 mm. I figure the AF has the same problem as we all have trying to focus an ultra wide lens. It is difficult.

Originally posted by Rondec

It is definitely harder to auto focus at 16mm than at 50mm. The focus points are too big to pick up contrast. This is usually the case at infinity focus and not with things that are closer. I think it is more an issue with the auto focus system than with the lens.

Well, it's indeed all the more strange that the problem revealed itself on the longer range: focusing at 16mm, no problem and at 50mm, no lock.

PentaxPoke · 12-27-2009, 05:48 PM

Originally posted by bc_the_path

It starts focusing after a moment or two even with a fully charged battery on a K20D.
The focusing is not fast by any standard and the SDM just fails to provide any confidence!
It is a difficult to describe feeling, I know.
Perhaps one can understand that more easily, if we talk about testing a car; sometimes you just "feel" that the car is not for you...

The lens is not good for manual focusing, either. The whole travel is about 90 degrees and there is no quick-shift.

I am still trying hard to love it but...

Bulent
Does yours focus any differently from the 50-135 in this video? I am curious. The video shows a k-7. It looks similar to the way my 50-135 focused before I sold it:

[YT]http://www.youtube.com/watch?v=ngUcQUchHEU[/YT]

Maybe if enough people post video of the way thier DA*'s focus we could see some similarities. I wish now in hindsight that I would have thought to video tape my SDM failures so others could see the intermittency and the "wakeup" procedures I had to go through.

bc_the_path · 12-29-2009, 11:40 AM

PentaxPoke:
>Does yours focus any differently from the 50-135 in this video?
Yes and no!
Mine starts after waiting for a second or two (abnormal and unacceptable, especially for a lens which was just repaired by the official Pentax Service) and focuses thereafter like that in the video.
The other camera (in the video) seems to focus much faster; I did not know that. Phew!

I am really disappointed with my lens and I am thinking of starting another thread on the reasons for this.

builttospill · 12-29-2009, 11:51 AM

Interesting video, although it's definitely not a comparison between the K-7 and 7D, it's a poor comparison of the 50-135, 18-250 and a 70-200, 17-55. They should get more comparable lenses; a similar focal length prime, the 50-135 and 70-200 aren't bad, but I think this is the first time I've seen the 18-250 in a comparison. Maybe a 16-45 should have been used with the 17-55.

PentaxPoke · 12-29-2009, 02:17 PM

Originally posted by builttospill

Interesting video, although it's definitely not a comparison between the K-7 and 7D, it's a poor comparison of the 50-135, 18-250 and a 70-200, 17-55. They should get more comparable lenses; a similar focal length prime, the 50-135 and 70-200 aren't bad, but I think this is the first time I've seen the 18-250 in a comparison. Maybe a 16-45 should have been used with the 17-55.

We can criticize the methodology all we want, but the best comparison is the 70-200 vs the 50-135, and it is very revealing. Remember the 70-200 is at a significant disadvantage! That lens is an f/4 and the 50-135 is an f/2.8. That means that in any scenario in the same light, the DA* lens has twice as much light to use for autofocus since AF is done with the lens at max aperture before it is stopped down to the exposure setting. To make matters worse, notice in the video that the 70-200 on the 7D focused more than twice as fast at EV1 as the 50-135 did in EV5. That is 4 stops less light, not even taking into account the f/2.8 vs f/4. If I am looking at that correctly, the Canon focused more than twice as fast as the Pentax, using 5-stops less light.

There is no sugar coating that. The Red Herring of "test methodology" doesn't work here. This is a significant weakness in Pentax AF.

builttospill · 12-29-2009, 03:01 PM

Yep, agreed. I hope 2010 brings better focusing for Pentax cameras (and lenses).

**Rondec** · 12-29-2009, 07:55 PM

My 50-135 does focus more quickly than that one demonstrated in the video. Not that the SDM is quicker, but there is not the same couple of pauses that I see on the video. That is not to say that it is as fast as the Canon 70-200 f4. Clearly to have focusing that fast, it would require new auto focus algorithims, as well as a faster in lens motor. Not certain when, or if that will happen, or if I can afford it if it does.

PentaxPoke · 12-29-2009, 08:20 PM

Originally posted by Rondec

My 50-135 does focus more quickly than that one demonstrated in the video.

Are you sure you were in the same light as the video? My DA* would do what you see in the video when the lighting was dim, like indoors. In bright light, it was still slow, but would not do that "start-stop-start-stop etc." motion.

asdf · 12-30-2009, 02:53 AM

Originally posted by PentaxPoke

Maybe if enough people post video of the way thier DA*'s focus we could see some similarities.

Based on all the videos I've watched, DA* 50-135 has the slowest or second slowest SDM motor--DA* 55 being the contender. DA* 300 f/4 is pretty fast...BTW, mine hasn't failed...yet...knock on wood.

**Rondec** · 12-30-2009, 09:37 AM

Originally posted by PentaxPoke

Are you sure you were in the same light as the video? My DA* would do what you see in the video when the lighting was dim, like indoors. In bright light, it was still slow, but would not do that "start-stop-start-stop etc." motion.

Hard to say. The issue is one of contrast, not necessarily of lighting. If I am locking on a contrasty thing, I get a lock without hesitation. On the other hand, if there isn't any contrast, then I have hesitation. I seem to have more issues with my 16-50 in low light than with 50-135.

PentaxPoke · 01-04-2010, 07:36 PM

So far it looks like 25 out of 96 votes (26%) show SDM failures. And that does not count several of us that have had multiple failures of the same type of lens since we cant vote more than once.

It looks like the percentages are not calculating properly. For example, there are 13 total votes regarding the 17-70f/4. The number of failures should be 15% so far for that lens. Not 2%. I assume that it is calculating based on total votes, but that is less useful IMO.

asdf · 01-04-2010, 10:46 PM

Originally posted by PentaxPoke

So far it looks like 25 out of 96 votes (26%) show SDM failures. And that does not count several of us that have had multiple failures of the same type of lens since we cant vote more than once.

It looks like the percentages are not calculating properly. For example, there are 13 total votes regarding the 17-70f/4. The number of failures should be 15% so far for that lens. Not 2%. I assume that it is calculating based on total votes, but that is less useful IMO.

There are 15 total votes (13 + 2) regarding 17-70 and the number of failures is 13.3...%. I voted for failure, btw.

In any event, the column with the percentages is totally useless.

View Poll Results: What Has Been Your SDM Experience?
DA* 16-50/2.8: No SDM problems	38	38.00%
DA* 16-50/2.8: Bad SDM	13	13.00%
DA* 200/2.8: No SDM problems	11	11.00%
DA* 200/2.8: Bad SDM	0	0%
DA* 300/4: No SDM problems	18	18.00%
DA* 300/4: Bad SDM	0	0%
DA* 50-135/2.8: No SDM problems	56	56.00%
DA* 50-135/2.8: Bad SDM	10	10.00%
DA* 55/1.4: No SDM problems	6	6.00%
DA* 55/1.4/2.8: Bad SDM	0	0%
DA* 60-250/4: No SDM problems	8	8.00%
DA* 60-250/4: Bad SDM	1	1.00%
DA 17-70mm/4: No SDM Problems	13	13.00%
DA 17-70mm/4: Bad SDM	2	2.00%
Multiple Choice Poll. Voters: 100. You may not vote on this poll

12-29-2009, 02:17 PM	#68
PentaxPoke Veteran Member Join Date: Jan 2008 Location: Oklahoma Posts: 1,411	Originally posted by builttospill Interesting video, although it's definitely not a comparison between the K-7 and 7D, it's a poor comparison of the 50-135, 18-250 and a 70-200, 17-55. They should get more comparable lenses; a similar focal length prime, the 50-135 and 70-200 aren't bad, but I think this is the first time I've seen the 18-250 in a comparison. Maybe a 16-45 should have been used with the 17-55. We can criticize the methodology all we want, but the best comparison is the 70-200 vs the 50-135, and it is very revealing. Remember the 70-200 is at a significant disadvantage! That lens is an f/4 and the 50-135 is an f/2.8. That means that in any scenario in the same light, the DA* lens has twice as much light to use for autofocus since AF is done with the lens at max aperture before it is stopped down to the exposure setting. To make matters worse, notice in the video that the 70-200 on the 7D focused more than twice as fast at EV1 as the 50-135 did in EV5. That is 4 stops less light, not even taking into account the f/2.8 vs f/4. If I am looking at that correctly, the Canon focused more than twice as fast as the Pentax, using 5-stops less light. There is no sugar coating that. The Red Herring of "test methodology" doesn't work here. This is a significant weakness in Pentax AF. Last edited by PentaxPoke; 12-29-2009 at 02:50 PM.

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12-21-2009, 11:39 AM	#61
bc_the_path Veteran Member Join Date: Mar 2007 Location: Ankara, Turkey Photos: Gallery Posts: 401	My 50-135mm has just been fixed. The price was €223 (plus shipping charges). It starts focusing after a moment or two even with a fully charged battery on a K20D. The focusing is not fast by any standard and the SDM just fails to provide any confidence! It is a difficult to describe feeling, I know. Perhaps one can understand that more easily, if we talk about testing a car; sometimes you just "feel" that the car is not for you... The lens is not good for manual focusing, either. The whole travel is about 90 degrees and there is no quick-shift. I am still trying hard to love it but... One thing is certain, though: If it fails again soon, I will not be surprised!!! Call me biased! ---- ADDED: A note on the poll statistics at the moment: The percentage of 16-50mm lenses with an SDM failure is 26% (12 of 45). The percentage of 50-135mm lenses with an SDM failure is 16% (10 of 63). The display is probably based on another count so the percentages look different there (and they do not add up to 100%). Last edited by bc_the_path; 01-03-2010 at 01:00 PM.

12-21-2009, 11:43 AM	#62
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by bc_the_path My 50-135mm has just been fixed. The price was €223 (plus shipping charges). It starts focusing after a moment or two even with a fully charged battery on a K20D. The focusing is not fast by any standard and the SDM just fails to provide any confidence! It is a difficult to describe feeling, I know. Perhaps one can understand that more easily, if we talk about testing a car; sometimes you just "feel" that the car is not for you... The lens is not good for manual focusing, either. The whole travel is about 90 degrees and there is no quick-shift. The lens does in fact have quick shift, as do all DA* lenses. Quote: I am still trying hard to love it but... One thing is certain, though: If it fails again soon, I will not be surprised!!! Call me biased!

12-21-2009, 12:09 PM	#63
bc_the_path Veteran Member Join Date: Mar 2007 Location: Ankara, Turkey Photos: Gallery Posts: 401	Canada Rockies: >The lens does in fact have quick shift, as do all DA* lenses. Of course it has! I think I was subconsciously trying to find more excuses for not using this lens

12-21-2009, 12:15 PM	#64
Bart Pentaxian Join Date: May 2007 Location: WW community of Pentax users Photos: Gallery \| Albums Posts: 2,646	Originally posted by Ash Bart, under what conditions did your old 16-50 not lock focus? Originally posted by Russell-Evans ... I looked through Bart's posts and I think this is the one he was talking about: Edit: I see you are talking about the issue with the returned "fixed" lens after it had been in for service as noted in this post. ... Sorry for the late response - different time zones. Russel is correct. that is what I was referring to. And to be clear, I haven't had this problem with the new copy (yet?) Originally posted by Canada_Rockies I wonder if it is due to the difficulty of focusing ultra wide lenses in general? Ihave not had too much difficulty with mine, but occasionally, I have to point it at something with some contrast, particularly at the wider angles, 16 - 18 mm. I figure the AF has the same problem as we all have trying to focus an ultra wide lens. It is difficult. Originally posted by Rondec It is definitely harder to auto focus at 16mm than at 50mm. The focus points are too big to pick up contrast. This is usually the case at infinity focus and not with things that are closer. I think it is more an issue with the auto focus system than with the lens. Well, it's indeed all the more strange that the problem revealed itself on the longer range: focusing at 16mm, no problem and at 50mm, no lock.

12-27-2009, 05:48 PM	#65
PentaxPoke Veteran Member Join Date: Jan 2008 Location: Oklahoma Posts: 1,411	Originally posted by bc_the_path It starts focusing after a moment or two even with a fully charged battery on a K20D. The focusing is not fast by any standard and the SDM just fails to provide any confidence! It is a difficult to describe feeling, I know. Perhaps one can understand that more easily, if we talk about testing a car; sometimes you just "feel" that the car is not for you... The lens is not good for manual focusing, either. The whole travel is about 90 degrees and there is no quick-shift. I am still trying hard to love it but... Bulent Does yours focus any differently from the 50-135 in this video? I am curious. The video shows a k-7. It looks similar to the way my 50-135 focused before I sold it: [YT]http://www.youtube.com/watch?v=ngUcQUchHEU[/YT] Maybe if enough people post video of the way thier DA*'s focus we could see some similarities. I wish now in hindsight that I would have thought to video tape my SDM failures so others could see the intermittency and the "wakeup" procedures I had to go through.

12-29-2009, 11:40 AM	#66
bc_the_path Veteran Member Join Date: Mar 2007 Location: Ankara, Turkey Photos: Gallery Posts: 401	PentaxPoke: >Does yours focus any differently from the 50-135 in this video? Yes and no! Mine starts after waiting for a second or two (abnormal and unacceptable, especially for a lens which was just repaired by the official Pentax Service) and focuses thereafter like that in the video. The other camera (in the video) seems to focus much faster; I did not know that. Phew! I am really disappointed with my lens and I am thinking of starting another thread on the reasons for this.

12-29-2009, 11:51 AM	#67
builttospill Pentaxian Join Date: Jun 2009 Location: Utah, Idaho Photos: Gallery Posts: 2,398	Interesting video, although it's definitely not a comparison between the K-7 and 7D, it's a poor comparison of the 50-135, 18-250 and a 70-200, 17-55. They should get more comparable lenses; a similar focal length prime, the 50-135 and 70-200 aren't bad, but I think this is the first time I've seen the 18-250 in a comparison. Maybe a 16-45 should have been used with the 17-55.

12-29-2009, 03:01 PM	#69
builttospill Pentaxian Join Date: Jun 2009 Location: Utah, Idaho Photos: Gallery Posts: 2,398	Yep, agreed. I hope 2010 brings better focusing for Pentax cameras (and lenses).

12-29-2009, 07:55 PM	#70
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,653	My 50-135 does focus more quickly than that one demonstrated in the video. Not that the SDM is quicker, but there is not the same couple of pauses that I see on the video. That is not to say that it is as fast as the Canon 70-200 f4. Clearly to have focusing that fast, it would require new auto focus algorithims, as well as a faster in lens motor. Not certain when, or if that will happen, or if I can afford it if it does.

12-29-2009, 08:20 PM	#71
PentaxPoke Veteran Member Join Date: Jan 2008 Location: Oklahoma Posts: 1,411	Originally posted by Rondec My 50-135 does focus more quickly than that one demonstrated in the video. Are you sure you were in the same light as the video? My DA* would do what you see in the video when the lighting was dim, like indoors. In bright light, it was still slow, but would not do that "start-stop-start-stop etc." motion.

12-30-2009, 02:53 AM	#72
asdf Veteran Member Join Date: Jan 2009 Location: Canada Posts: 1,252	Originally posted by PentaxPoke Maybe if enough people post video of the way thier DA's focus we could see some similarities. Based on all the videos I've watched, DA 50-135 has the slowest or second slowest SDM motor--DA* 55 being the contender. DA* 300 f/4 is pretty fast...BTW, mine hasn't failed...yet...knock on wood.

12-30-2009, 09:37 AM	#73
Rondec Loyal Site Supporter Join Date: Mar 2009 Location: Gladys, Virginia Photos: Gallery Posts: 27,653	Originally posted by PentaxPoke Are you sure you were in the same light as the video? My DA* would do what you see in the video when the lighting was dim, like indoors. In bright light, it was still slow, but would not do that "start-stop-start-stop etc." motion. Hard to say. The issue is one of contrast, not necessarily of lighting. If I am locking on a contrasty thing, I get a lock without hesitation. On the other hand, if there isn't any contrast, then I have hesitation. I seem to have more issues with my 16-50 in low light than with 50-135.

01-04-2010, 07:36 PM	#74
PentaxPoke Veteran Member Join Date: Jan 2008 Location: Oklahoma Posts: 1,411	So far it looks like 25 out of 96 votes (26%) show SDM failures. And that does not count several of us that have had multiple failures of the same type of lens since we cant vote more than once. It looks like the percentages are not calculating properly. For example, there are 13 total votes regarding the 17-70f/4. The number of failures should be 15% so far for that lens. Not 2%. I assume that it is calculating based on total votes, but that is less useful IMO.

01-04-2010, 10:46 PM	#75
asdf Veteran Member Join Date: Jan 2009 Location: Canada Posts: 1,252	Originally posted by PentaxPoke So far it looks like 25 out of 96 votes (26%) show SDM failures. And that does not count several of us that have had multiple failures of the same type of lens since we cant vote more than once. It looks like the percentages are not calculating properly. For example, there are 13 total votes regarding the 17-70f/4. The number of failures should be 15% so far for that lens. Not 2%. I assume that it is calculating based on total votes, but that is less useful IMO. There are 15 total votes (13 + 2) regarding 17-70 and the number of failures is 13.3...%. I voted for failure, btw. In any event, the column with the percentages is totally useless.