[house]

I agree that it may well be marketing. Tamron not mentioning that one of the asphericals is anomalous dispersion is odd though. As far as I understand this is an expensive material.

Stevebrots posts are hilarious I have no idea what he's on about but lets leave it.

Perhaps these optical diagrams are just pure marketing that reveal only a minimum about the actual optics. Still find that strange for such a product as a lens.

[Rondec]

It is the same lens with different coatings. I'm guessing the Pentax version flares a bit less than the Tamron branded version due to these coatings, but otherwise there is probably little difference.

I do shoot with it and it is decent. I still would be interested if Pentax would do their own 24-70 f2.8 like their new release of the DA *16-50 PLM. It just has weakish borders wide open.

[zapp]

Just words…
Pentax coatings align well with other Pentax glass. Exterior design is more Pentax like. Only one lens here fits Pentax.

[Bertrand3000]

The two diagrams looks to be identical. The name given are probably more marketing than technical, I would not worry about such a "difference". Except the coatings, the lenses should be the same.

[stevebrot]

The brief (and not altogether helpful) summary from Ricoh on their lens marketing document indicates that it’s a glass type, not a manufacturing process. Moulded lenses may be of a number of different types of glass (as, indeed, is the new pentaprism in the K-3iii, compared with its predecessors).

I would expect this ^ ^ ^ might put much of the matter to rest, but perhaps not.


Steve

[RobA_Oz]

The two diagrams looks to be identical. The name given are probably more marketing than technical, I would not worry about such a "difference". Except the coatings, the lenses should be the same.

I doubt anyone is particularly worried about any detail differences, but curiosity is the common element that drives most of us out to take photos in the first place. It can, obviously, also lead us up the occasional blind alley.

[house]

This article about the da*1650 discusses some of the glass types involved. Beware of poor translation. Abnormal -> anomalous for instance.

Link by ooku

https://mp-weixin-qq-com.translate.goog/s/te4rqbbZi7J0YvNkb7U41A?_x_tr_sl=zh...o=ajax,nv,elem

Makes you wonder if tamron has a similar patent explaining the glass types to such a level of detail.

[RobA_Oz]

This article about the da*1650 discusses some of the glass types involved. Beware of poor translation. Abnormal -> anomalous for instance.

Link by ooku

https://mp-weixin-qq-com.translate.goog/s/te4rqbbZi7J0YvNkb7U41A?_x_tr_sl=zh...o=ajax,nv,elem

Makes you wonder if tamron has a similar patent explaining the glass types to such a level of detail.

Translation oddities aside, the detail is fascinating, including the number and variety of special glasses used in that design. The comment about the glass used by Sigma being responsible for some of their odd colourings is interesting. I’d actually noticed something like this with their 8-16.

[house]

My take away is that the specified glass types are indeed different and of consequence. There is however a chance (even if it goes against all self interest ) that Tamron omits naming the expensive glass in their lens to simplify the marketing material.

That is however a bit like a restaurant putting only the term "beef" on the menu and serving wagu without informing the customer.

[bdery]

To me, as an optical designer, looking at these imprecise renderings, I see no difference between the two.

The companies will not reveal their trade secrets on these drawings.

The names they use for their exotic glass is marketing, not technical. Don't put too much weight on it.

[ehrwien]

The names they use for their exotic glass is marketing, not technical. Don't put too much weight on it.

Velcom to de hydraulic press channel, today ve have some exotic Pentax glass elements that vant us to buy them, so ve must deeeal with it.

You Tube

You Tube

You Tube

You Tube

You Tube

You Tube

sorry for taking that literally

[house]

The names they use for their exotic glass is marketing, not technical. Don't put too much weight on it.

So do you think Pentax actually isn't using anomalous dispersion glass in their lenses? Because anomalous dispersion is a technical glass type right? Total noob at this stuff but have seen it mentioned in what appeared to be academic papers (not Pentax related )

Seems dangerous to claim it in marketing material without cover?

---------- Post added 07-19-21 at 11:59 AM ----------

Remembered this from a previous post. It shows that Tamrons does use and specify anomalous dispersion for some of its lenses. Doesn't say they have to say every time they use it of course.

[bdery]

Velcom to de hydraulic press channel

Well played!

So do you think Pentax actually isn't using anomalous dispersion glass in their lenses?

I didn't say that. I said the choice of words is marketing. Another company might call it something different.

Because anomalous dispersion is a technical glass type right?

Not really, no.

Dispersion is a phenomenon, not a type of glass. "Anomalous" is an adjective added to it. It's not one single type of glass, and the rest of the design elements (thickness, curvature of that element, relation to the others, etc) will influence its behaviour.

[house]

Well played!



I didn't say that. I said the choice of words is marketing. Another company might call it something different.



Not really, no.

Dispersion is a phenomenon, not a type of glass. "Anomalous" is an adjective added to it. It's not one single type of glass, and the rest of the design elements (thickness, curvature of that element, relation to the others, etc) will influence its behaviour.

Im pretty sure I've seen Schott PDFs with product numbers detailing anomalous partial dispersion. But only in passing as I'm not really knowledgeable.

Of course the glass then has to be shaped etc but thats besides the material itself. I'll have a look at that ooku linked breakdown of the dfa1650 again because it had info and numbers for the glass types.

[house]

I've done some more lazy googling and found Hoya patents for anomalous partial dispersion glass recipes dating back to the early seventies. As well as lots of recent info from Schott, Leitz etc. So its most certainly a (actually many different, a whole category) type of material that is different from other optical speciality formulations.