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05-25-2021, 04:37 AM - 1 Like   #16
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QuoteOriginally posted by Henrico Quote
The second diagram would never result in sharp images, so this is clearly a mistake. My opinion is that both lenses share exactly the same formula, only the coatings and the layout differ somewhat.
It could be accurate, although it would require a few changes in the optical construction of the lens since it is a retro-focus design. The Only example of this I can think of right now is the contrast between the early 7 and 8 element 50mm f/1.4 takumars. The lens design was reduced in its complexity - one cemented group of different refractive indices was replaced with a larger solid element with recalculated geometry and the optical design changed to compensate.

In this case I would say - judging from the optical schematics presented here, there is no evidence that suggests pentax has changed the optical formula to compensate for the removal of an element from the design, it could very well be a mistake.




---------- Post added 2021-05-25 at 10:20 PM ----------

QuoteOriginally posted by house Quote
I thought anomalous dispersion was more expensive and rare than ed glass but what do I know.
They are both expensive, depending upon quality and the exact chemistry needed* to fit the manufacturers specifications. With exotic glass types factors such as the ability to be made in various sizes and in large batches without material defect, the ability to be formed and annealed without dimensional instability and ability to be ground to specific tolerances and polished to a high finish: taking these factors into account high grade ED glass is the more difficult of the two materials to work with as it is quite fragile.

* Lens elements made for the Early Leica 50mm f/1.2 Noctilux ASPH had to be made in crucibles made of solid platinum as it was the only material inert enough at those temperatures to not affect the chemistry of the molten glass. A lot of glass types are made these days, and glass manufacturers like Schott and Ohara have expansive catalogues of glass types and seldom have to develop an entirely new glass types from scratch. Lenses these days are designed around what is available and easy to source.


Last edited by Digitalis; 05-25-2021 at 04:59 AM.
05-25-2021, 05:45 AM   #17
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Perhaps I'm wrong but third party manufacturers rarely use anomalous dispersion glass? I havent made a survey but I've wondered about it. Leica and Pentax seems to like it.

Edit: the dfa 70-210 has two such elements according to the diagrams but Tamron doesn't mention it. Pentax also adds "extra " to the LD glass.




Last edited by house; 05-25-2021 at 05:54 AM.
05-25-2021, 07:01 AM - 1 Like   #18
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You can't just take out the rear element without any changes to the rest of the rear group, so this is obviously some mistake
05-25-2021, 08:22 AM   #19
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I knew that déjà vu feeling didn't come out of nowhere: All three FA Limiteds to be updated + K-1 Mark II J-Limited 01 - Page 38 - PentaxForums.com

05-25-2021, 08:51 AM   #20
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I sorta just checked and they both the diagrams from here look the same to me...

So...did anyone notice that the FA 77mm f/1.8 Limited is officially discontinued? (Probably old news, but in the spirit of things...)


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05-25-2021, 09:21 AM   #21
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QuoteOriginally posted by aslyfox Quote
even if there is the same number of elements, this appears to be a true change:



is that different " language " for the same thing or a true difference ?

I'm keeping my MIJ black FA 31mm Limited regardless
It is a true difference as I understand it, normal dispersion gives CA and with the anomalous type CA is less. That is the difference and I think that it is on the same level pricewise.
05-25-2021, 09:23 AM - 1 Like   #22
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QuoteOriginally posted by Andrea K Quote
yep, PF has to use this for the HD:



and this for the smc:

So the TLDR here is that they are the same (possibly except for the naming if the ED element), but one of the diagrams published early on was wrong?

05-25-2021, 09:28 AM   #23
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QuoteOriginally posted by Adam Quote
So the TLDR here is that they are the same (possibly except for the naming if the ED element), but one of the diagrams published early on was wrong?
The smc hasn't ED elements and the HD hasn't one less element, both diagrams on PF are wrong.

p.s.: about the name the only hint about the optical construction is AL that is for Aspherical Lens, ED is not present.

Last edited by Andrea K; 05-25-2021 at 09:39 AM.
05-25-2021, 10:01 AM   #24
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QuoteOriginally posted by Adam Quote
So the TLDR here is that they are the same (possibly except for the naming if the ED element), but one of the diagrams published early on was wrong?
QuoteOriginally posted by Andrea K Quote
The smc hasn't ED elements and the HD hasn't one less element, both diagrams on PF are wrong.

p.s.: about the name the only hint about the optical construction is AL that is for Aspherical Lens, ED is not present.
Well, that is strange. An hour ago I checked the database and I could swear there were correct images for both lenses. Now, that is no longer the case.


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05-25-2021, 10:08 AM   #25
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I'm sittin' here like:
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05-25-2021, 10:20 AM   #26
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AHAHAHAHAHAHAH

p.s.: check the url of the images
05-25-2021, 10:30 AM   #27
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A diagram doesn't prove anything. To make sure they are the same lenses, someone has to put them on a scale and compare the weight
05-25-2021, 11:10 AM   #28
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QuoteOriginally posted by AfterPentax Mark II Quote
Maybe that is why it is cheaper than the older version! It is not only missing one element, the extraordinary low-dispersion element has changed to an anomalous dispersion glass one, which if I have it right is cheaper as well. Explains a lot, wonder about the other Ltd's that did become cheaper and got HD coating.
Does anyone have a definitive answer regarding the price anomalies between the old smc coated variants and the new HD versions? One would immediately think that the new HD coated versions of the 'new' Limited lenses should by all intents and purposes be more expensive, not less expensive. What strange marketing rationale is at play? Is there anything else about the HD coated lenses that we don't know?
05-25-2021, 11:39 AM   #29
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QuoteOriginally posted by Jeff Quote
Does anyone have a definitive answer regarding the price anomalies between the old smc coated variants and the new HD versions? One would immediately think that the new HD coated versions of the 'new' Limited lenses should by all intents and purposes be more expensive, not less expensive. What strange marketing rationale is at play? Is there anything else about the HD coated lenses that we don't know?
HD is cheaper than the coatings on the smc ltds. Makes sense that the lenses are cheaper.
05-25-2021, 01:07 PM   #30
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QuoteOriginally posted by house Quote
HD is cheaper than the coatings on the smc ltds. Makes sense that the lenses are cheaper.
Thanks for your reply. Does that mean lower quality? May I ask the source of your information?

I'm still not convinced by the marketing strategy. Better usually means more expensive. Is that the case in this instance?
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