[Brightcolours]

We do know that the glass is the same. Only you make up that it must have a special Penatx sauce, because "Pentax".

Like I said before, you can't just exchange an element with the same shape element with different light passing properties and expect good results. That you think one has to be "an optical expect" to know that just shows your lack of understanding of anything related to lenses.

What Pentax calls "SP" is the same as others (Canon, Tamron, Nikon for instance) use, and Tamron specifically mentions about this lens. Claiming it must be different because "Pentax" is just silly. And what Pentax' marketing department calls "HD" is their own issue. That they are happy to call Tamron's coatings of this lens "HD" is upto them.

I scaled the Tamron and rebadged "Pentax"Tamron published MTF charts so they match height and width, to make it easier for you to see that the rebadged Tamron is a rebadged Tamron:



It is a rebadge of a Tamron. Of course it is a customisation for Pentax, just like the Canon and Nikon versions can not be the same, and Pentax has no way of dealing with in lens IS, it is a bit more customised than when you compare the Canon and the Nikon versions.

And even you must be aware of that this is not a PLM lens, right?

And it certainly is not a lie that the Tamron is a better lens (does not shrink to under 135mm at MFD like the Pentax, does not have the CA issues the Pentax has https://www.ephotozine.com/article/penta...view-29351 , and renders a lot nicer).