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My 16-50 returned from repair (SDM)

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I'm with you that Pentax could act better in this but I move on and forget my frustrations. That's easy now because the lens is outstanding now. Another thing is that I have had it completely with Pentax Benelux "de Beukelaer" witch try to make an extra money out f it. Double price when compared to Pentax Germany and Asahi Pentax Ltd. And they even don't answer my question why the price is that high.

Regards

****
brecklundin said:
From my reading about the reputation of Asahi Photo Ltd in the UK, I agree they seem to have a reputation of being fair and honest in their dealings. So, like you, I take that as a very positive sign. It is a shame that Pentax doesn't make an announcement that the motors were updated or whatever they really did. Maybe even give owners of existing SDM glass bought during whatever period the problematic components a special service deal. Maybe a something like $150/lense including taxes and postage if serviced directly by Pentax so as not to compete with the small service companies like Asahi Photo. Or even a free inspection, cleaning and adjustment service then if the lense needs it's SDM motor replaced give the customer a special deal on the replacement or whatever. It sure would go a long way to reviving the market for SDM glass.

No matter this is really nice news to read and I will keep my fingers and toes crossed in hopes when I am ready to add new glass later next year that the comments wrt SDM glass are more to share the great shots those lenses delivered than for AF failures... :D I am just cautious simply because I had one die on me right after purchase, which could easily happen with ANY AF glass made by anyone so in my case it was likely just a bad lense even if the failure was the SDM sub-system. Still I am a bit wary in using another SDM for a while...it's been around 18-months since my 50-135 failed so in another 10-months or so I think we'll have a clearer idea of what's up in that world.

All I know is if SDM is "fixed" and with the K5, next year is gonna be expensive for camera gear!! ahhhh...poor-me....snickersnicker... :D
**** eduard said:
"On the SDM Motors problem, it is only the first production motors which may
had the problem, the new batches , I have had no problems. “

Regards

****
brecklundin said:
thanks for sharing what you learned in this adventure. It would seem to support that one reads fewer posts of failed SDM from more recent purchases. Still it is going to take at least another year to learn if this is really the case or that fewer people are actually buying the SDM lenses so we read less and less about it. Only time will tell for sure.

--
Real men shoot Pentax because we were born with our own Canons!!
{Ok...ok, some of use just shoot with a PnS but it always makes me happy! :D}

Beligerent commenters are just afflicted with SFmS (Stud Field Mouse Syndrome)
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--
Real men shoot Pentax because we were born with our own Canons!!
{Ok...ok, some of use just shoot with a PnS but it always makes me happy! :D}

Beligerent commenters are just afflicted with SFmS (Stud Field Mouse Syndrome)
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Jono Slack said:
HI There
I'm new to Pentax, and I love my K5.

I also wanted a 16-50, but the two copies I've had have been seriously decentred; one was soft on the right, the other on the left - not where you might expect, but at 35mm -50mm and f5.6.
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I find this very surprising, as I was under the impression that the de-centering problems had long since been solved. Were these new or used lenses that you bought?

My first DA*16-50 had a major centering defect, so I returned it and waited 6 months before buying another, which is perfect. It has been performing flawlessly for nearly two years. I just hope that the SDM problem was solved by the time that mine was manufactured. I would advise against giving up on this lens, as it is wonderful for general purpose photography. I keep it on my camera 95% of the time.

Rob
 
Robgo2 said:
Jono Slack said:
HI There
I'm new to Pentax, and I love my K5.

I also wanted a 16-50, but the two copies I've had have been seriously decentred; one was soft on the right, the other on the left - not where you might expect, but at 35mm -50mm and f5.6.
Click to expand...
I find this very surprising, as I was under the impression that the de-centering problems had long since been solved. Were these new or used lenses that you bought?
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Hi Rob

Both new stock from a main dealer - actually, I've had 3 of them (I had one briefly with a K7 in the spring - but I didn't test it beyond being unsatisfied with soft edges).

They were both fine at the ends of the zoom range, but were bad around 28-40mm and worse at f5.6 than they were wide open - one of them was soft on the right, the other on the left.

I wonder how many people actually test them at these sort of focal lengths and apertures? Despite the fact that they are the ones used more often, there is just a general assumption that if they're good at the extremes they'll be okay in the middle.

--
Jono Slack
http://www.slack.co.uk
 
The edges of the frame will be softer even on a good copy of this lens because:
  • The focus plain is not completely flat, it is slightly curved towards the corners.
  • Light falloff on the corners (vignette) also causes some softness towards the edges/corners.
  • It is a zoom lens and all zooms are a compromise.
With decentering you should notice it less as you stop down as the DoF will increase meaning the previously out of focus sections will come into focus.

This lens is very sensitive and it is very easy to get something out of focus shooting wider open than f5.6 in my experience with my K10D.

--
Regards,
Tyr

My Photos:
http://www.pentaxphotogallery.com/danielfranco
 
HonourableTyr said:
The edges of the frame will be softer even on a good copy of this lens because:
  • The focus plain is not completely flat, it is slightly curved towards the corners.
  • Light falloff on the corners (vignette) also causes some softness towards the edges/corners.
  • It is a zoom lens and all zooms are a compromise.
With decentering you should notice it less as you stop down as the DoF will increase meaning the previously out of focus sections will come into focus.

This lens is very sensitive and it is very easy to get something out of focus shooting wider open than f5.6 in my experience with my K10D.

--
Regards,
Tyr
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Hi Tyr -
I've been checking out lenses for 10 years now - I do know what I'm doing! :)
one of the lenses was soft on the right hand side.
The other lens was soft on the left hand side.
it was worse at f5.6, and in the middle of the zoom range.

I'm perfectly aware of the curvature of field, and also of the fact that one cannot expect miracles with zooms.

In this case the simple test was to take a vertical shot (on a tripod) of a flat target from about 3 metres. Then to turn the camera over so that the other side was on top. Doing the same test at infinity really proved the point.

at 35mm and f5.6 the whole frame should be sharp - and, indeed the whole of the top of the frame was sharp in one photo, and the whole of the bottom in the other (and vice versa). The dealer checked both lenses out as well, and agreed with the diagnosis.

It's worth mentioning that at 16-24mm and at 50mm the slightly soft edges were pretty much even on both sides of the frame.

The other lenses I've bought (60-250, 35 macro, 100 macro 15 limited) don't show any signs of decentering, although the 15 is badly soft at the corners right up to (and including) f8 :(

all the best
--
Jono Slack
http://www.slack.co.uk
 
**** eduard said:
After allmost 3 years my 16-50 died completely.
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I think you are being too reasonable. Considering that Canon replaced the sensor on my Ixus free of charge after SIX years, I think it's completely outrageous that Pentax didn't offer to fix your motor free of charge after just three years of use.

Just as with SDM, the failure of the Sony sensor in my Ixus could not be predicted, yet Canon did the sensible thing and extended the warranty for this particular part.
--
Mike
http://flickr.com/rc-soar
 
Jono Slack said:
at 35mm and f5.6 the whole frame should be sharp - and, indeed the whole of the top of the frame was sharp in one photo, and the whole of the bottom in the other (and vice versa). The dealer checked both lenses out as well, and agreed with the diagnosis.
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Jono Slack said:
all the best
--
Jono Slack
http://www.slack.co.uk
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I'm just saying that it can't be an aperture specific, or for that matter worsened, problem. If it happens at f5.6 it should be worse at f4, etc. It cannot get worse as you stop down as you are increasing DoF and focusing the light via the aperture.

Is that not correct?

My original 16-50 was de-centred and I got a lot of fringing around objects that couldn't be fixed in PP which meant smaller prints only :(

Not sure about my current one, every so often I notice the right side of the frame is out of focus, however, when I carefully try and replicate it I can't unless I tilt the camera/lens which means it is probably the way I hold the camera.

--
Regards,
Tyr

My Photos:
http://www.pentaxphotogallery.com/danielfranco
 
HonourableTyr said:
Jono Slack said:
at 35mm and f5.6 the whole frame should be sharp - and, indeed the whole of the top of the frame was sharp in one photo, and the whole of the bottom in the other (and vice versa). The dealer checked both lenses out as well, and agreed with the diagnosis.
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HonourableTyr said:
all the best
--
Jono Slack
http://www.slack.co.uk
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I'm just saying that it can't be an aperture specific, or for that matter worsened, problem. If it happens at f5.6 it should be worse at f4, etc. It cannot get worse as you stop down as you are increasing DoF and focusing the light via the aperture.

Is that not correct?
Click to expand...
Well, that's what I thought too, but I think it's to do with the increased depth of field making the edges generally better, and thus the blurring more obvious where it occurs (both edges are still slightly soft wider than f5.6). It certainly did seem to be the case.

I saw a similar problem with the Nikon 17-55 some years ago (I guess it might be a similar design?).

I do quite a lot of portrait landscapes (if you see what I mean) with just a sliver of land at the bottom of the shot - it's not much good if that's a blurry sliver!
HonourableTyr said:
My original 16-50 was de-centred and I got a lot of fringing around objects that couldn't be fixed in PP which meant smaller prints only :(

Not sure about my current one, every so often I notice the right side of the frame is out of focus, however, when I carefully try and replicate it I can't unless I tilt the camera/lens which means it is probably the way I hold the camera.
Click to expand...
Might be I suppose - not in this case though - especially at infinity - maybe you should try a few shots at infinity.

I'm sorry if I've disturbed your equilibrium!

all the best
--
Jono Slack
http://www.slack.co.uk
 
Jono Slack said:
Well, that's what I thought too, but I think it's to do with the increased depth of field making the edges generally better, and thus the blurring more obvious where it occurs (both edges are still slightly soft wider than f5.6). It certainly did seem to be the case.

I saw a similar problem with the Nikon 17-55 some years ago (I guess it might be a similar design?).

I do quite a lot of portrait landscapes (if you see what I mean) with just a sliver of land at the bottom of the shot - it's not much good if that's a blurry sliver!

Might be I suppose - not in this case though - especially at infinity - maybe you should try a few shots at infinity.

I'm sorry if I've disturbed your equilibrium!

all the best
--
Jono Slack
http://www.slack.co.uk
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Interesting, I am quite happy with most of the stuff I get from my 16-50. It is just the odd shot where I think "WTF? How did that happen?".

Some of the time it is my error, or my hat's. My hat has a tendency to change the aperture setting when shooting in portrait with the grip on.

Sometimes I just can't figure out what caused it.

--
Regards,
Tyr

My Photos:
http://www.pentaxphotogallery.com/danielfranco
 
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