[Brightcolours]

Then you might want to haunt Nikon forums telling people how their Nikkors 70-200 VR II are no good. And to start a petition to redefine "optically superior" as "lack of focus breathing".

The Nikkor AF-S 70-200mm f2.8 VR II has been criticised for years exactly for the same thing. Under which rock have you been hiding? The Nikkor AF-S 70-200mm f2.8 FL VR no longer has that serious issue its forebear had, and is an excellent lens. So is the new Nikkor Z 70-200mm f2.8 VR, btw.

The new Canon RF 70-200mm f2.8 L IS USM does have the negative focus breathing issue the Pentax 70-200mm f2.8 has, which is its big (only?) downside, too.

And it is not about "lack of focus breathing". The Tamron 70-210mm f4, be is the rebadged "Pentax" or the Canon or Nikon version, stays close to 200mm and so has the other direction of focus breathing. Its FOV narrows towards MFD, where the Pentax f2.8 has a FOV that widens towards MFD. 

Hope to have educated you a bit.

[Kunzite]

Tell me, why exactly do you think I mentioned the Nikkor, if not for knowing about it's focus breathing issue? It didn't rain, there was no full moon and the wind didn't blow from north-west - to mention some other possible reasons.
The question remains, did you or did you not troll Nikon forums telling people how the Nikkor is a "worse" lens? Or maybe this is a special service for Pentax?

Educated... boy, you are deluded.

[Brightcolours]

This is what you wrote, troll. "Then you might want to haunt Nikon forums telling people how their Nikkors 70-200 VR II are no good. And to start a petition to redefine "optically superior" as "lack of focus breathing".

Take some time to read what you actually wrote.

My reaction to the Nikon thing: I told you, in response, that that Nikkor has been criticised exactly for what I criticise this Pentax for. Nikon forums have discussed this many times, this is why I wonder what rock you have been hiding under. I have written about it many times, also about this issue where Sigma and Tamron 70-200mm lenses have had this issue. And superzooms. And the Canon EF 70-300mm f4-5.6 L IS USM.

Then you type this: "lack of focus breathing". That is what I tried to educate you on, apparently in vain, apparently i an "deluded" thinking you can be educated... The Tamron does focus breathe, it has no lack of focus breathing. Because it stays close to 200mm focussing towards MFD, its FOV narrows. The issue is not focus breathing, it is the kind of focus breathing. This Pentax dives under 135mm towards MFD and widens the FOV significantly, which is not very desirable when one buys the lens for "200mm" and not "135mm". So yeah, tried to educate you on focus breathing, in vain.

And, troll Kunzite, lately Canon introduced the Canon RF 70-200mm f2.8 L IS USM. Great lens (renders nicer than the Pentax, does not have the CA issue the Pentax has (according to the review I linked to in a post above)), but I noticed the negative issue of its design: FOV widening significantly towards MFD, and pointed it out on OL. Klaus also added a mention to this to the review of this lens, on my instigation.

Do some introspection, perhaps?

[Kunzite]

So I am the troll, not the guy spewing crap about a system he has no interest in. Riiiight. You started by pointing fingers to imaginary fanboys, so I'm not surprised. What's next? Come on, you can do more name calling - all while bashing this pesky brand, of course. But no parroting, that's lame.

Why won't you read what you wrote? You said the Nikkor was criticized, not that you criticized it yourself.
And you might be surprised, but you're just a small online existence among many others - I don't watch what you're doing, I only have the total displeasure of meeting you here because this is a Pentax forum I'm occasionally visiting (and you're occasionally trolling). If you indeed criticized the Nikkor, me not knowing is not the same as "hiding under a rock". Delusion much?

What's the source for the 135mm? Prove every claim of yours, as I can't trust anything you're saying.
But anyway, the D FA* having a focus breathing issue doesn't mean it's anything other than an excellent lens.

Focus breathing is nothing more than a change in focal length as you're focusing. The Tamron keeping close to its nominal focal length means it doesn't have a focus breathing issue.
It's really simple, don't try pretending you're some sort of an expert. You're not fooling anyone.

[Brightcolours]

So I am the troll, not the guy spewing crap about a system he has no interest in. Riiiight. You started by pointing fingers to imaginary fanboys, so I'm not surprised. What's next? Come on, you can do more name calling - all while bashing this pesky brand, of course. But no parroting, that's lame.

Why won't you read what you wrote? You said the Nikkor was criticized, not that you criticized it yourself.
And you might be surprised, but you're just a small online existence among many others - I don't watch what you're doing, I only have the total displeasure of meeting you here because this is a Pentax forum I'm occasionally visiting (and you're occasionally trolling). If you indeed criticized the Nikkor, me not knowing is not the same as "hiding under a rock". Delusion much?

What's the source for the 135mm? Prove every claim of yours, as I can't trust anything you're saying.
But anyway, the D FA* having a focus breathing issue doesn't mean it's anything other than an excellent lens.

Focus breathing is nothing more than a change in focal length as you're focusing. The Tamron keeping close to its nominal focal length means it doesn't have a focus breathing issue.
It's really simple, don't try pretending you're some sort of an expert. You're not fooling anyone.

You spew crap indeed, no idea why you do that. You say the rebadged Tamron lens is not a badged Tamron lens. You claim the lens may have different optics, even though there is no evidence for that and the evidence against that gets just shoved aside. 
You call objective observations "a lie".

Then you go on calling me a troll because, in part, I point out the negative focus breathing the Pentax 70-200mm has, and to trap me, ask if I say the same about a past Nikkor. When I make your trap worthless, you say "delusion much?".... Yep, you sure are a trolling.

And the published Pentax/Ricoh specs are the source for the <135mm. Proof? The How about the product website? The rebadged Tamron stays close to 210mm, and achieves 0.32x at 95cm. Lets assume that the focal length at 95cm focus distance still is 200mm. So, 0.32x for 200mm at 95cm distance. The Pentax does 0.13x @ 1.2mm focus distance. That will make 0.13 / 0.95 * 1.20 = 0.164x at 0.95m focus distance.
So, rebadged Tamron f4 reaches 0.32x at 0.95mm for 200mm focal length. The Pentax f2.8 would reach about 0.164x at 0.95mm. 200 / 0.32 x 0.164 = 102mm. 102mm is indeed smaller than 135mm. 

Even if we we would make the nonsense assumption that the Tamron remains 210mm at MFD we still end up with just 107mm at MFD for the Pentax.

Now you call yourself educated, again.

[mst]

Enough. Both of you calm down please.

[Kunzite]

Let's cut the ^&%: (don't quite remember how the saying goes)
- the Pentax D FA* 70-200 f/2.8 is optically superior to the Tamron. Yes, it renders nicely. No, the Tamron isn't bad at all.
- the D FA 70-210 is a customization of the Tamron 70-210, because there are changes other than what's required to convert it to a Pentax mount. I expect at least better flare resistance.
- the Pentax version might use different glass types in some of its elements, and Pentax coatings. Note the might; note that I said "I don't quite believe this" - this is a hypothesis I specifically want to be tested before saying it's true.

I'm leaving this for people to see what I'm actually claiming. As mst requested, the discussion is over.

[Mistral75]

Considering a complex optical system with several lens elements moving independently one from another, there is no direct relation between minimum focusing distance, maximum magnification and focal length. Other parameters have to be considered.

Anyway, most people speaking of variation in the angle of view, and not in focal length, when they talk about focus breathing, one can simplify things and consider each of the two lenses as if it were made of one single lens element. In this case, there is a direct relation between minimum focusing distance (MFD), maximum magnification (MM) and focal length at minimum focusing fistance (FL@MFD):

FL@MFD = MFD x MM.

HD Pentax-D FA 70-210 mm f/4 ED SDM WR:   MFD = 0.95m   MM = 0.32x   ==>   FL@MFD = 304mm. The angle of view decreases with the focusing distance.

HD Pentax-D FA★ 70-200mm f/2.8 ED DC AW:   MFD = 1.2m   MM = 0.13x   ==>   FL@MFD = 156mm. The angle of view increases when the focusing distance decreases.

[Kunzite]

Mistral, what matters is that the Pentax D FA* 70-200 f2.8 has a focus breathing issue (if you care about it), and the Tamron/Pentax D FA 70-210 f4 doesn't. This is even explained on Ricoh Imaging's website.
Why are we discussing it here? Because it's a red herring; the original claim was about background rendering which is very good on the D FA*.

For a Pentaxian, having another convincing choice is a good thing. Except for the price, but that's the easiest to "fix".
We're not in a hurry to "prove" any of our convincing choices "worse" than the other.

[Mistral75]

Mistral, what matters is that the Pentax D FA* 70-200 f2.8 has a focus breathing issue (if you care about it), and the Tamron/Pentax D FA 70-210 f4 doesn't. This is even explained on Ricoh Imaging's website.
(...)

Both have actually and that matters if you are into video.

As for stills, the extra reach of the 70-210mm close to MFD is not a problem (just zoom out if it bothers you), the enlarged field of view of the 70-200 might be.