(01-28-2020, 07:26 AM)Brightcolours Wrote: 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).
Yeah, we're having this discussion because I'm a Pentax fanboy and you're not an anti-Pentax troll
Usually it's the third-party makers who are putting as many labels as possible on their lenses.
Yes, an optical expert would be able to say if changing two elements - with the possibility of slightly altering the shape of any elements but not their positioning - could work.
You can not even figure out that it's not about "one element with the same shape".
The MTF graphs were copy-pasted from Tamron. Note that I never claimed improvements in MTF anyway (I'm not claiming anything of this sort, but I guess that's too complex for someone stuck in a "you're saying this because it's Pentax" routine).
Coatings differences can be tested, at least if the coloring is different. Flare resistance is likely improved on the Pentax anyway, because of the added baffle(s).
Of course it's not a PLM lens, but your hypothesis was that Pentax added the focus limiter not because AF speed is something the Tamron is not great at - but because Pentax cameras are slower.
Well, Pentax cameras do benefit greatly from fast AF lenses. Have you ever tried a recent Pentax with the PLM lens?
A lie repeated a thousand times is still a lie. Even if "supported" by convenient selection of 2 criteria and pretending to see more subjective aspects of image quality.
Oh, and that review? You must believe I cannot read - it is praising the Pentax.
(01-28-2020, 02:40 PM)Brightcolours Wrote: Both Pentax-rebranded Tamron and Tamron use fuorine coatings for the front element, and both state as such on their product pages.
I'd guess everyone
is using some sort of dirt repelling coating.
Pentax developed their own version, that's why SP is a "Pentax-original". And HD coatings, the secret is in the application method. There are coating-related patents assigned to Ricoh Imaging, this is an ongoing research.
Your point should be limited to the SP/HD labels possibly
being reused for the equivalent Tamron coatings. Which would get you to the same point I'm making, that we should try testing this.
(01-28-2020, 02:08 PM)davidmanze Wrote: Maybe there are more differences than we think between the Pentax and the Tamron........ or is it just erroneous information at this point in time !!
According to Ricoh's specs ........ the lens is made or uses magnesium alloy .....
.... yet Tamron's reviewers talk about a plasticy feel !!....
Errors e.g. in copy-pasting are not impossible. Neither is altering the material of some components.
We truly need more information.