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06-19-2010, 12:54 PM   #46
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QuoteOriginally posted by habsfanusa Quote
I've been following this thread with great interest (and increasing disgust at Pentax). Sorry for the melodrama but here's my quick story:...
So then I started my lens research, from the ground up - and when i started checking on others' experience with my must-have walkabout, the DA* 16-50 (an utter ABSENCE of QC at Pentax in a lens that lists at ≈$1,200), i was frankly shocked.
My astonishment only grew as I've followed these threads here - the comment earlier in this thread about an (apparently scratched) element (in a lens bought new !) resembling an astrology map in particular comes to mind.
[I even emailed Pentax a week ago asking for reassurance regarding the DA*16-50 QC question, and got a lame response to the effect that SDM motors from their subcontractor two years were a problem that was then solved. I replied with a literally "are you kidding me - do you guys read these forums, you must be aware that the problem is far more encompassing than that" - type communication, sent twice - but no reply. Interesting !]
So my new-found friends, PLEASE jump in with some guidance.
For instance, am i misguided regarding the in-camera HDR ? I prefer to do the bracketing in the shot, not post-processing. I do a lot of landscapes, i understand the need for a tripod. And any/every comment regarding lens options would be welcome. I am partial to "OEM" lenses over Tamron, Sigma et al - bit not absolutely opposed.
Thank you !
Though the experience of the thread opener has indeed the power to deter a would-be-Pentax-buyers, I do not think it is by any means representative. - Which most of the answers in this thread will also emphasize.

The 55-300mm lens which is on your wish-list is also one, of which I never saw any seriously bad comment. The 16-50 is another story. My own copy died within weeks of buying it, but is working fine after warranty repair.

So, yes, Pentax QC is not as good as it should be and for many years it wasn't. But in all fairness, I have seen similarly bad experiences with people buying Canons or Nikons on the web as well.

For instance: the slight misalignement in aperture blades should certainly not be there. But I have seen so many lenses with similar asymmetries, that I have the feeling, that this can be caused by many different things, including a hard knock or whatever. And even though several of my own lenses show similar asymmetries, I cannot say, that the image quality was compromised by that.

Fot third party lenses: I have been using third party lenses since starting photography nearly 30 years ago. At the beginning I had some bad experience with low cost brands (the Cosina among them) and in film days only bought the Tokina ATX lenses besides Pentax ones, not the least because of their superb build-quality.

In digital days I soon realized, that Sigma had taken on the challenge and provided some very fine glass. Now I use five Sigma EX lenses besides my Pentax glass and two Tamrons. All in all the Sigmas provide (in my personal opinion) excellent value with much better built than Tamrons and the image quality is just about as good as it gets. Tamron makes good glass, but is let down by the plasticky feeling, that goes with them.

I do not hesitate to buy Pentax lenses and also don't hesitate about Sigma. My decisive point is always availability: if I cannot get a certain lens from Pentax, I buy Sigma. And so far I have never been disappointed and had only two QC problems (the said DA 16-50 and one Sigma Apo-tc falling apart) - which I find acceptable, considering the amount of equipment I store in my cupboards...

Ben

06-20-2010, 07:46 PM   #47
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Mine isn't a horror, per se, but it was very informative.

I bought a Rokinon 28mm on eBay. I got a really good deal, and it arrived in pristine condition, not a speck of dust on the lens at all. Really a beautiful lens.

I mounted it, and it seemed fine at f/2.8, but other apertures didn't work. I took it off and found that the aperture blades wouldn't move, they were stuck. I got the blades to start moving, and one of them was loose. It wasn't moving right.



I decided to take the lens apart and see what I could do. I managed to get the entire lens apart and finally got to the aperture assembly. If you've never taken a lens apart, the aperture blades have two pegs that ride in grooves, and when the ring moves, the blades close or opens. Now, when you pull out that assembly, they pop right out of the assembly, and they are almost impossible to put back into the housing without them deciding to jump out and scatter. I must have tried to put them back in about 30 times (no kidding) before I finally gave up and decided that it was going to be a fixed aperture lens.

So, I put everything back together and put it on to test. Works pretty well for an f/2.5-f/2.8ish lens. Until I tried to get to infinity focus. No go. When I put reassembled the front and back of the lens, I must have missed the correct thread, so it doesn't focus right.

These are the two parts that aren't lined up correctly.


So, now I have a lens that has no aperture blades, and can't focus to infinity. Not a huge loss for a $10 lens, but I was really looking forward to using it. I just got a replacement for it and it works perfectly.
06-20-2010, 09:35 PM   #48
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Wow, wish I hadn't looked into this thread, I just checked my new DA70 Limited... and it indeed has EASILY 300% more dust and strange particles inside the lens than even my very old M 50mm I bought off the marketplace. Although I think its still a very fine piece of glass. My 18-55 WR looks pristine though... for a lens that costs 1/5 the price.

<sigh> I guess I might ask for an exchange. Its just silly for a brand new lens to have that kind of debris inside.
06-20-2010, 09:54 PM   #49
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I only had one bad experience with a new lens, and that was a Zeiss/Cosina. I got a copy that had so much dust it looked like somebody blew dust inside it. I exchanged it and the second one still had a dozen of dust specks, but I deemed that to be acceptable. The most disappointing thing was that on contacting Zeiss they seemed to think it's a rather normal issue. Now I know a little dust doesn't affect images, but I expect more from a new lens.

One suspicion I have is that this might actually be due to the store selling me a lens that was used a bit. I wish lenses would come with a manufacturer's seal.

06-21-2010, 07:53 AM   #50
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QuoteOriginally posted by Laurentiu Cristofor Quote
I only had one bad experience with a new lens, and that was a Zeiss/Cosina. I got a copy that had so much dust it looked like somebody blew dust inside it. I exchanged it and the second one still had a dozen of dust specks, but I deemed that to be acceptable. The most disappointing thing was that on contacting Zeiss they seemed to think it's a rather normal issue. Now I know a little dust doesn't affect images, but I expect more from a new lens.

One suspicion I have is that this might actually be due to the store selling me a lens that was used a bit. I wish lenses would come with a manufacturer's seal.
Well, the thing is that lenses aren't sealed, with the exception of weather sealed lenses. Dust is going to get sucked in and pushed out with the action of zooming or focusing.

Canon has a 100-400L lens that is known as the "Dust Pump", because it is well known for sucking in dust. It's a push-pull lens, so can generate a fair amount of suction.
06-21-2010, 09:43 AM   #51
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There is an opening at the rear of every K mount lens for the aperture lever to work, dust will settle on the 2 glass surfaces near the aperture blades. It's just a matter of time.
06-21-2010, 10:14 AM   #52
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Original Poster
QuoteQuote:
kalison Wow, wish I hadn't looked into this thread, I just checked my new DA70 Limited... and it indeed has EASILY 300% more dust and strange particles inside the lens than even my very old M 50mm I bought off the marketplace. Although I think its still a very fine piece of glass. My 18-55 WR looks pristine though... for a lens that costs 1/5 the price.
I too am amazed by this. My 18-55 AND 50-200 WR kit lenses were pristine...but so much drama with my Limited buying. And I'm not talking about shining a flashlight down the barrel to find fault (I think a tiny bit of TINY dust particles is pretty much unavoidable), but just holding the glass up to a ceiling light would show so much nasty inside my lenses that I never even bothered to put them on my camera.

Since I've had so many issues with unclean lenses, I've decided I'm going to keep this CLEAN copy of the FA 31 Limited, but have B&H send it back to Pentax to have the blades realigned.

On the other hand...my 100 Macro WR is taking some AMAZING pics!!! Only had to return that one ONCE to get a good copy. :P

Last edited by porterHause; 06-21-2010 at 10:23 AM.
06-21-2010, 10:25 AM   #53
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QuoteOriginally posted by alohadave Quote
Well, the thing is that lenses aren't sealed, with the exception of weather sealed lenses. Dust is going to get sucked in and pushed out with the action of zooming or focusing.
That's true, but we're talking about new lenses here. Even if they were used for QA purposes, they shouldn't have sucked as much dust as I've seen in that Zeiss.

06-21-2010, 01:27 PM   #54
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Just curious: I'd read that the FA 43 aperture was just like that at f/2.8. Mine's the same. Does anybody have an FA 43 with a different aperture shape at f/2.8?
06-21-2010, 01:43 PM   #55
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QuoteOriginally posted by farfisa Quote
Just curious: I'd read that the FA 43 aperture was just like that at f/2.8. Mine's the same. Does anybody have an FA 43 with a different aperture shape at f/2.8?
Mine was like PorterHause's FA43 when I bought it in 99/1, and this is how it looks now after I rearranged the blades. Not perfect, but much better than b4.

06-21-2010, 02:45 PM   #56
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QuoteOriginally posted by wlachan Quote
Mine was like PorterHause's FA43 when I bought it in 99/1, and this is how it looks now after I rearranged the blades. Not perfect, but much better than b4.
Wow! Nice work!
06-21-2010, 10:31 PM   #57
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Hey! I just checked mine and it's the same! Three of the blades are out. Apparently, f2.8's (based on the settable apertures on the aperture ring) the worst case. From f4 onwards, it's pretty much nice angles. Somehow the blades are a little short and hence end abruptly when not adjusted to perfection. It's a copy I had gotten from B&H in January. Seems like it's a very widespread issue in the last of the MIJ batches.

I do have another earlier copy which has pretty much perfect alignment. I am definitely keeping this baby.

wlachan: Your arrangement is as good as perfect! Did you introuduce any scuffs or scatches during the process? Feeling real tempted to have a go at it? What kind of tools do you need? You should have documented the process. Ha!
06-21-2010, 11:37 PM   #58
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I hear you. I don't have a DSLR yet, but my lens karma just plain sucks, at least when it comes to 200MM ones.

First 200MM lens I purchased it was sold as "near perfect" and it was chock FULL of fungus when it arrived. No returns policy, $20 right down the drain.

2nd 200MM lens, supposedly in VGC, I worked for 8 hours doing some retouching on photos to earn it. It looks okay, there in the shop, but two days later it's stuck in such a bad way that they tell me it will take $75 to fix it and the guy won't take it back so I've basically worked for nothing all day.

3rd 200MM zoom. Came in the swap with a Vivitar K-mount camera that I got for doing more digital retouching, different place, total crap, fungus, mega dust, lousy lens, no loss there. It was free, the camera was the actual trade, so I couldn't complain, but it was definitely disappointing.

I think I've spent about a year working or trying to swap for a decent 200MM lens to fit one of my cameras, no kidding.

The only thing that makes me feel better is knowing it's not several hundred dollars of digital lens I've wasted my money on!

I will keep this post in mind when I finally get my DSLR though. I'm going to buy all the lenses with the camera and double check every one of them before I leave. If I have to take a trip elsewhere when it comes time to buy, I will, but I don't think I'll be buying online after all. Sounds like it's not such a great idea....
06-22-2010, 08:08 AM   #59
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QuoteOriginally posted by scorpioh Quote
wlachan: Your arrangement is as good as perfect! Did you introuduce any scuffs or scatches during the process? Feeling real tempted to have a go at it? What kind of tools do you need? You should have documented the process. Ha!
I didn't scuff the lens and the procedure was straight forward. Things to remove in order:

1) unscrew the front retaining ring
2) remove 3 screws & the filter rim
3) unscrew the front lens group using a lens wrench

You can now loosen the screws (but not remove) on the brass clip that's holding the aperture blades disc in place, move the disc around and see if you can fix the aperture shape. If not, goto 4. Remember, the shape is affected by gravity. That means you will have to hold the lens in shooting position for accurate result.

4) remove the large brass ring using a sharp round nose metal pliers (I hate this part, you will see why)
5) remove the disc and blades using curved tips plastic tweezers (metal tweezers will scuff the parts if not careful)
6) rearrange the blades, put back the disc and brass ring clip, tighten the screws (don't over tighten btw) and pray
7) goto 4 if failed
8) threadlock the screws on the disc when done

Don't blame me if anything bad happened.

Last edited by wlachan; 06-22-2010 at 08:14 AM.
06-22-2010, 08:34 AM   #60
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QuoteOriginally posted by wlachan Quote
I didn't scuff the lens and the procedure was straight forward. Things to remove in order:

1) unscrew the front retaining ring
2) remove 3 screws & the filter rim
3) unscrew the front lens group using a lens wrench

You can now loosen the screws (but not remove) on the brass clip that's holding the aperture blades disc in place, move the disc around and see if you can fix the aperture shape. If not, goto 4. Remember, the shape is affected by gravity. That means you will have to hold the lens in shooting position for accurate result.

4) remove the large brass ring using a sharp round nose metal pliers (I hate this part, you will see why)
5) remove the disc and blades using curved tips plastic tweezers (metal tweezers will scuff the parts if not careful)
6) rearrange the blades, put back the disc and brass ring clip, tighten the screws (don't over tighten btw) and pray
7) goto 4 if failed
8) threadlock the screws on the disc when done

Don't blame me if anything bad happened.
Hi Wlachan, thanks for your detailed description but I am a bit unclear without pics. Let me focus on the first three steps assuming it could solve the problem. May I know How do I remove the front retaining ring? Also, where can I get the lens wrench? Thanks.
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