Pentax Quality Control Strikes Again

Started Apr 23, 2015 | Discussions
KentG Veteran Member • Posts: 4,638
Re: Pentax Quality Control Strikes Again

Throwing out the old Roman aquaduct subject, you are correct as the dirt in the foreground is much weaker on the left side.

Kent Gittings

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RichRMA Veteran Member • Posts: 4,073
Re: Pentax Quality Control Strikes Again

Did Tokina make this one too?

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OP Joseph Tainter Forum Pro • Posts: 11,082
Re: Pentax Quality Control Strikes Again
1

RichRMA wrote:

Did Tokina make this one too?

I am not certain that the DA 16-85 is a Pentax design. Maybe it is, maybe it isn't. It doesn't matter. The problem comes in sloppy manufacturing, and Pentax certainly manufactures the optics.

Tokina never made optics for Pentax. It was the other way around.

Joe

RichRMA Veteran Member • Posts: 4,073
Re: Pentax Quality Control Strikes Again

Joseph Tainter wrote:

RichRMA wrote:

Did Tokina make this one too?

I am not certain that the DA 16-85 is a Pentax design. Maybe it is, maybe it isn't. It doesn't matter. The problem comes in sloppy manufacturing, and Pentax certainly manufactures the optics.

Tokina never made optics for Pentax. It was the other way around.

Joe

Thanks, so the only thing they share is the optical design.

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OP Joseph Tainter Forum Pro • Posts: 11,082
Re: Pentax Quality Control Strikes Again

RichRMA wrote:

Joseph Tainter wrote:

RichRMA wrote:

Did Tokina make this one too?

I am not certain that the DA 16-85 is a Pentax design. Maybe it is, maybe it isn't. It doesn't matter. The problem comes in sloppy manufacturing, and Pentax certainly manufactures the optics.

Tokina never made optics for Pentax. It was the other way around.

Joe

Thanks, so the only thing they share is the optical design.

For the joint Pentax-Tokina lenses, that is correct. It is my understanding that Pentax manufactured the optics for Tokina for the joint lenses.

Of the joint lenses, Tokina designed the 12-24. Pentax designed the other ones.

Pentax has historically gotten long wide-to-tele lenses from Tamron. Tamron often uses a 62 mm. filter size, which Pentax has never used for its own lenses. So I suspect that the 18-135 is a Tamron design (even though Tamron doesn't offer a lens of its own like this). The DA 16-85 has a 72 mm. filter size, which Pentax has also never used for its own designs. That makes me wonder if this lens is by either Tamron or Tokina. On the other hand, Pentax had never made a lens with a 55 mm filter size. Then they made the DA 20-40, which has this filter size. So it might be that Pentax is venturing into filter sizes that it hasn't used before. It really doesn't matter. The DA 16-85 is reportedly a fine lens, whoever designed it, if you can get a good copy. I'll keep trying.

Joe

DAVID MANZE Veteran Member • Posts: 5,876
Re: Pentax Quality Control Strikes Again

awaldram wrote:

DAVID MANZE wrote:

awaldram wrote:

DAVID MANZE wrote:

awaldram wrote:

Joseph Tainter wrote:

I just got a DA 16-85. As with any new Pentax lens, I immediately took it out for a brick wall test. Sure enough, it is optically decentered, with bad weakness on the right side.

That's my second bad Pentax lens (out of two new lenses purchased) since last summer.

It's going back.

Joe

I think Joe your version of acceptable is not the same as Pentax's , This isn't meant as a criticism just a fact.

Joe's lens was not tested optically........they don't check every lens optically just an occasional sample! . there's just a quick mechanical check.

...........so it comes off the line and goes into the box ...

So how would Pentax have known whether it was good or not?......

You perhaps are not aware how manufacturing works in the modern age

Perhaps I know a little more about it than you think. Maybe you could pinpoint where the optical errors are coming from?

because it's in lens element element cementing.

Here's a link to a latest little device, this would help I think.

https://www.youtube.com/watch?v=rffVOoOLVqE

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RichRMA Veteran Member • Posts: 4,073
Re: Pentax Quality Control Strikes Again
2

They're probably using some 15 year old in an open-air factory in Vietnam to cement the optics.

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Jim King
Jim King Veteran Member • Posts: 8,582
Re: Pentax Quality Control Strikes Again

Joseph Tainter wrote:

(snip)

The DA 16-85 is reportedly a fine lens, whoever designed it, if you can get a good copy. I'll keep trying.

I believe that this is potentially  a fine lens.  I was lucky; I hope that you will be too, with your next copy.

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RichRMA Veteran Member • Posts: 4,073
Re: Pentax Quality Control Strikes Again
2

Nikon's 16-85 is an exceptional lens, someone should compare the Pentax to it.

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Gosman Contributing Member • Posts: 925
Re: Pentax Quality Control Strikes Again

I've been told that I over analyize photography too much.  Now I have met someone that is worst than me!  I buy good lenses and if they look good and sharp in the middle and everything else looks decent, I'm OK with it.  I do use the LensAlign system to set my camera to the lens.  But decentering and Off balance?  Come on.

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awaldram
awaldram Forum Pro • Posts: 13,270
Re: Pentax Quality Control Strikes Again

DAVID MANZE wrote:

awaldram wrote:

because it's in lens element element cementing.

Here's a link to a latest little device, this would help I think.

https://www.youtube.com/watch?v=rffVOoOLVqE

How that different from Pentaxs' jig

http://www.cloudynights.com/topic/345452-separation-of-a-doublet-and-re-cementing/

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DAVID MANZE Veteran Member • Posts: 5,876
Re: Pentax Quality Control Strikes Again

awaldram wrote:

DAVID MANZE wrote:

awaldram wrote:

because it's in lens element  cementing.

Here's a link to a latest little device, this would help I think.

https://www.youtube.com/watch?v=rffVOoOLVqE

How that different from Pentaxs' jig

http://www.cloudynights.com/topic/345452-separation-of-a-doublet-and-re-cementing/

Good one Andrew!

I think the answer is that the rhythm of the music is faster with the Pentax jig and the glue's dry when the music stops!

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Qwntm Veteran Member • Posts: 6,165
Re: Pentax Quality Control Strikes Again

Joseph Tainter wrote:

I just got a DA 16-85. As with any new Pentax lens, I immediately took it out for a brick wall test. Sure enough, it is optically decentered, with bad weakness on the right side.

That's my second bad Pentax lens (out of two new lenses purchased) since last summer.

It's going back.

Joe

Dang. My recent experience has been the opposite. I'm 3 for 3. My 15mm HD, 20-40 HD and 70 HD were perfect right out of the box. And I tested them pretty hard too. All bought in the last few weeks.

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OP Joseph Tainter Forum Pro • Posts: 11,082
Re: Pentax Quality Control Strikes Again

Qwntm wrote:

Joseph Tainter wrote:

I just got a DA 16-85. As with any new Pentax lens, I immediately took it out for a brick wall test. Sure enough, it is optically decentered, with bad weakness on the right side.

That's my second bad Pentax lens (out of two new lenses purchased) since last summer.

It's going back.

Joe

Dang. My recent experience has been the opposite. I'm 3 for 3. My 15mm HD, 20-40 HD and 70 HD were perfect right out of the box. And I tested them pretty hard too. All bought in the last few weeks.

Edward, I have those same three lenses, and mine were all good--except my DA 70 needs +7 focus adjustment on every camera.

Joe

DAVID MANZE Veteran Member • Posts: 5,876
Re: Pentax Quality Control Strikes Again
1

Qwntm wrote:

Joseph Tainter wrote:

I just got a DA 16-85. As with any new Pentax lens, I immediately took it out for a brick wall test. Sure enough, it is optically decentered, with bad weakness on the right side.

That's my second bad Pentax lens (out of two new lenses purchased) since last summer.

It's going back.

Joe

Dang. My recent experience has been the opposite. I'm 3 for 3. My 15mm HD, 20-40 HD and 70 HD were perfect right out of the box. And I tested them pretty hard too. All bought in the last few weeks.

Fixed focal lenses tend not to have the same problems, but you did well with the 20-40HD!

The more the zoom range the more demanding the lens alignment, if I remember rightly you were returning some a while back.

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