Tamron 28-200

BTW. When I look at the pictures on the above mentioned website I do see a difference in the construction between the Pentax 28-200 and my Tamron 28-200.
With the Pentax 28-200 the focus ring moves when the zoom is extended. With my Tamron the focusring stays where it is. I got the Tamron model 371D.
[edit] from what I can see on the web, my Tamron is a newer revision of the 28-200 on which the Pentax one is based[/edit]

Thankyou Glyn, that certainly settles the question of the coating.
I don't know about ascertaining the year of manufacture from the serial number but I do know that the lens creep that you describe is quite common with the early Tamrons, the later AF models feature a zoom-lock switch.

As far as I know, there have been five AF versions of the Tamron:

Model 71D featuring 2 hybrid-aspherical elements
Model 171D one standard element replaced with LD (Low Dispersion) glass and named 'Super'
Models 571D and 271D cosmetic restyling (271D silver bodied)
Models 371D and 471D (silver) more restyling, constant MOD throughout zoom range, addition of zoom-lock. Re-named 'Super II-Macro'
Models AO3 and AO3S (silver) - here we see a change in the optical configuration (15 elements in 14 groups as opposed to 16/14 for the earlier models).
These are XR Macro lenses - the filter size is reduced from 72 to 62mm, the lens is 25% smaller and 27% lighter, there is a third aspherical element, the LD element and one standard element have been replaced with 2 XR (Extra Refractive Index) elements.

The Pentax version most closely resembles the earlier models ie. no zoom-lock and whether it's a first or second generation would depend on whether it features an LD (ED in Pentax lingo) element.

Yes, the Pentax obviously doesn't feature the constant MOD that your Super II does and must therefore be based on either the original or 'Super' version.

Unless of course, it has moved simply because it's focussed in the macro range - perhaps they all do that!
The absence of the zoom-lock would certainly suggest that the Pentax is no later than the Super.

Well if you take the Pentax SMC FA 28-200 and shoot the sun what you'll see is a lot of flare...

My assumption is, and I could be quite wrong, that when Pentax use an existing design from someone else such as Tamron or Tokina they either contract out their requirements or buy in the lens cell and coat it with their own SMC coatings. Or perhaps even contract out the SMC process - it is, after all, just a specification.

In any event I would expect any SMC Pentax lens to be Super-Multi-Coated, and this does seem to be borne out by the similar transmission propertiues from lens to lens. That is, the colour balance, etc.

The 28-200 has lots of elements, so even with the SMC coating I would expect some degree of flare. There was some flare with the 15mm f3.5 as well, although it can be used creatively.

Ok, I took a shot at the sun today with the Tamron 28-200. I'll put it into my pbase account later. But first I have to get some food into myself