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01-04-2013, 08:34 PM   #16
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Though its odd that a lot of lens brands offer the same combinations of focal length and speed, there is more to a lens than just that. But in photography there is mixing and matching going on all the time. Just look at how many brands use Sony sensors, for example.

01-04-2013, 08:49 PM   #17
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who makes what for whom?

QuoteOriginally posted by Colbyt Quote
Well at least it is not yet as bad as 2 stroke string trimmers. All those suckers go down the same Chinese assembly line. The plastic surrounds and decals are the only real difference.r
Ford and Mazda come to mind
01-04-2013, 09:31 PM   #18
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QuoteOriginally posted by Franky2step Quote
Ford and Mazda come to mind
Indeed! Though that is less so now that Ford has divested most of its interest in Mazda.


Steve
01-05-2013, 01:33 AM   #19
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QuoteOriginally posted by Adam Quote
The optical design of the 100mm dates back to the 80s hehe. The DFA and FA versions actually share the same optics.
But why the FA is much sharper and bigger? Not only sharper, it has less aberations and fringe.

QuoteOriginally posted by lesmore49 Quote
Are you relatively new to Pentax ?
A couple of years, why?

QuoteOriginally posted by JinDesu Quote
Closest of your choices, with the same groups and elements, but different filter diameter and generally a different shape.

Would be highly unlikely, considering it's rear focus motor, different number of groups of elements, and I don't think lens construction works that way.

The Sigma 2.8-4.0 came out after the Pentax 17-70. Also different number of groups of elements. Not the older one either, because that one had 15 elements, while the DA 17-70 has 17 elements.

Definitely not the Tokina, which has 9 blade aperture vs the 8 in the DFA

The easiest thing to do is to compare lens construction diagrams. I think most of the Pentax lenses have lens diagrams available for viewing.

About 18-135 - If we look at the lens it is 18mm with streching to 135mm, my theory is that removing some elements from the long end made the lens 135mm instead of 250mm and that's why the 18-135 is so poor performer after 50mm. Sigma 18-250 also look like possible donor, it even zooms the right way(like the pentax).

My point for this thread was - does pentax develops lenses now days or they use other companies for the job and just re badge them.


Last edited by simbon4o; 01-05-2013 at 01:51 AM.
01-05-2013, 10:18 AM   #20
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QuoteOriginally posted by simbon4o Quote
About 18-135 - If we look at the lens it is 18mm with streching to 135mm, my theory is that removing some elements from the long end made the lens 135mm instead of 250mm and that's why the 18-135 is so poor performer after 50mm.
Do you own the 18-135? My 18-135 performs fine throughout the zoom range, so I don't place much credence in your theory.
01-05-2013, 10:25 AM   #21
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You can't just remove elements and expect it to work - that's not how lens construction is. The zoom is a relationship between two or more elements within the lens, and simply removing elements won't change that relationship to reduce zoom. If you remove elemets (or add) you change the whole optical formula.

And technically Pentax still makes lenses. Look at the Q lenses. Look at the DA 560mm. Consider the upcoming XS lenses. Look at the new 645D lenses.
01-05-2013, 10:30 AM   #22
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QuoteOriginally posted by MPrince Quote
Do you own the 18-135? My 18-135 performs fine throughout the zoom range, so I don't place much credence in your theory.
I can say that I have tried it. If you can compare it to those tourist zooms like 18-250/18-270 I bet that the 18-135 is worse after 50mm, much worse.

01-05-2013, 11:16 AM   #23
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QuoteOriginally posted by simbon4o Quote
But why the FA is much sharper and bigger? Not only sharper, it has less aberations and fringe.
The size is just a design choise, and it was a time when large lenses was cool.

The optical difference (I guess you are looking at photozone test), it's probably because of the RoHS directive that limited the use of heavy metal (not the music) in production of electronic products. RoHS recast: implications for optical materials

But it might also just be a simple sample variation.
01-05-2013, 12:16 PM   #24
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QuoteOriginally posted by simbon4o Quote
I can say that I have tried it. If you can compare it to those tourist zooms like 18-250/18-270 I bet that the 18-135 is worse after 50mm, much worse.
I don't have an 18-250, but I do have a DA 50-200. My 18-135 is better at 135 than my 50-200 at 138, so if you were to make that bet with me, you'd lose.
01-05-2013, 02:49 PM   #25
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QuoteOriginally posted by lesmore49 Quote
I agree with you....but I do think that Pentax is also the developer of the 12-24mm lens.
Well, I am repeating second hand information, but that says the DA 12-24 is licensed from Tokina, while the 10-17, 35 limited, 16-50 and 50-135 were licensed the other direction.
01-05-2013, 03:01 PM   #26
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QuoteOriginally posted by simbon4o Quote
But why the FA is much sharper and bigger? Not only sharper, it has less aberations and fringe.



A couple of years, why?




About 18-135 - If we look at the lens it is 18mm with streching to 135mm, my theory is that removing some elements from the long end made the lens 135mm instead of 250mm and that's why the 18-135 is so poor performer after 50mm. Sigma 18-250 also look like possible donor, it even zooms the right way(like the pentax).

My point for this thread was - does pentax develops lenses now days or they use other companies for the job and just re badge them.

First of all, the DFA 100mm WR is just as sharp as the older versions, it has pretty much added a weather sealed body and rounded blades (and lacks an aperture ring and focus limiter). I doubt you could tell the difference between the two in most situations.

Secondly, lens design is not a matter of taking an existing lens design and just dropping out (or adding elements) to get a new focal length. Most of the work is now done on computers. For lenses like the 50mm lenses from Pentax, the designs usually have their roots in much older designs, but they are Pentax designs. Some are designed brand new, like the DA *55 and FA limiteds. The 18-135 was supposed to have been designed brand new, although by someone relatively inexperienced since Hirakawa Jun had been let go by Hoya.
01-05-2013, 03:02 PM   #27
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QuoteOriginally posted by Rondec Quote
Well, I am repeating second hand information, but that says the DA 12-24 is licensed from Tokina, while the 10-17, 35 limited, 16-50 and 50-135 were licensed the other direction.
These lenses were developed co-operatively with Tokina. I have the DA version of the 12-24 and 16-50 and used to have the 50-135. The DA/DA* versions have proprietary proprietary SMC coatings. Tokina coatings are used on the other mounts.
01-05-2013, 03:08 PM   #28
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QuoteOriginally posted by simbon4o Quote
I'm sure about some of them Philippian trolls.
Bible Trolls?
01-05-2013, 04:59 PM   #29
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QuoteOriginally posted by Canada_Rockies Quote
These lenses were developed co-operatively with Tokina. I have the DA version of the 12-24 and 16-50 and used to have the 50-135. The DA/DA* versions have proprietary proprietary SMC coatings. Tokina coatings are used on the other mounts.
Right. I think Tokina and Pentax have quite different versions of these lenses, but with the same basic formula. However it is my understanding that Pentax owns the patents to all but the 12-24.
01-05-2013, 08:25 PM   #30
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QuoteOriginally posted by simbon4o Quote
I can say that I have tried it. If you can compare it to those tourist zooms like 18-250/18-270 I bet that the 18-135 is worse after 50mm, much worse.
My 18-135mm is sharper than my DA 18-250mm at the same focal lengths. Here's the proof:
https://picasaweb.google.com/bonhommed/18135Vs18250?authkey=Gv1sRgCNzC5b_4_qXRqQE#
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