Having found another Tamron brochure, I can now confirm that the 28-200 does indeed feature BBAR multi-coating.

I assume the Pentax has SMC and I agree with George's reasoning as to why, but my FA lens brochure circa 1995 does not list the 28-200 (first produced around '98 I think) - can anyone confirm one way or the other?

Fernando, I have a number of 15-20 year old Tamron Adaptall 2 lenses and there's no sign of the BBAR coating deteriorating on any of them.

SMC (Super Multi-Coating) is, as we all know, absolutely superb and one of Pentax's strengths.

If the Tamron does not have SMC (and I believe that it doesn't), then it will have Tamron's own BBAR (Broad-Band Anti-Reflection) coating, which is also highly regarded.
From a Tamron product brochure; "....as many as 7 coating layers are deposited on each glass-to-air surface. The result: significantly increased light transmission, virtual elimination of flare and internal reflections, and a beautifully crisp and accurate rendition of even the most subtle colours in your pictures."

SMC might be the best but I doubt there'll be much, if any noticeable difference in performance.

I must admit that Tamron don't claim that you can stub a cigarette out on it though

Interestingly, Photodo give the Pentax a poor score of 1.7, while the Tamron scores a more respectable 2.7

For it's zoom range, it's an admirable performer and won numerous awards.
I'm sure you'll be pleased with it and it'll look like a big pro lens....even if it doesn't quite perform like one!

Sounds like you bagged a bargain, let us know how you get on - digital, film or both?

Steve, that certainly looks like a good price (Pentax list them at £199.99) and being weatherproof, they should last for many years.
The Pentax range is pretty extensive:
http://www.pentax.co.uk/binoculars/search.php?cat_id_99=1&action=search

Personally, I don't find binoculars to be very comfortable to use and I certainly wouldn't want to lug a large heavy pair around for any length of time. I imagine too that it'll be pretty tough trekking through the rain-forest and so my advice would be for your wife to try a few different models before making a final decision.
Optically, of course, Pentax will be excellent but just how many models you'll be able to find in local stores for your wife to try and get a 'feel' for remains to be seen.

Given the requirements and the price, I think I might be quite tempted to go for that model too!

Yes, that basically sums it up.

Think of it as a standard 2x converter (1.7x isn't far off) and then imagine it as an AF lens in it's own right. It has the same AF coupling and electronics as an F series lens. The front of the converter is effectively a KA mount (no AF coupling this time but yes, full aperture control), so any lens attached to it is set manually to infinity and the adapter does the AF work.
For close-up work, you can set the focus of the lens to a shorter distance and thereby limit the AF range and bring into focus subjects that are too close for the adapter to resolve sharply with the lens set to infinity.

I recently tried the adapter with my 75-250 f3.8/4.5 and the camera had no difficulty whatsoever, the result at the long end was soft but this was largely down to camera-shake (bear in mind that we are talking of an effective focal length of almost 640mm on my DL) and I'm sure that with the usual precautions, that can be eliminated - the AF system certainly locked on very positively.

Incidentally, the adapter is also usable with the camera in MF mode or on a manual body (a Super A or MZ-M, for example) and you can adjust the adapter's setting by turning the focus mechanism with a watchmakers' screwdriver before mounting it onto the camera.

Zooms do tend to be less sharp toward the extremes and then there's the inevitable camera shake to deal with too.
I have to admit that it's a bit hit and miss with my 500mm f8 mirror but not a problem at all with my 75-250mm f3.8/4.5.

My favourite tele lens, for use with the AF converter is a 135mm f2.5. At 230mm for film and 345mm for digital, it's more than long enough for most tele uses and still provides a nice bright viewfinder image.

As with most things AF, the performance of the converter depends more on subject brightness/contrast than anything else.
The AF 1.7x converter is primarily designed for use with fast prime lenses but can still be quite effective with slower zooms.
Even in low-light situations, you can switch the camera to MF and simply focus the lens the old-fashioned way and still benefit from the multiplication factor (use AF to focus on a distant light source to ascertain infinity and then switch to manual).

I must say that the converter was designed for the SF range of 35mm cameras but performs even better on later bodies due to their improved AF systems

Yes, any K-mount lens will fit but the available auto functions will vary.

KA series lenses are best for manual focus, F and FA series for autofocus.

You're obviously aware that the DA lenses are autofocus but optimised for DSLRs and so you have a very wide choice of available optics.
I see no reason why a regular KA mount teleconverter shouldn't be just as useful with a DA lens as with a traditional 35mm film lens.......unless there's an issue with aperture couplings, but I wouldn't know as I don't have any DA lenses

I can certainly recommend the Pentax AF 1.7x converter though, it's excellent!

I'm English but it confuses me too, I mean what on earth is the point of silent letters
American-English is more phonetically correct, og-course - but not as quaint!

Good luck with the cameras, it sounds as though you've got some really terrific photo opportunities ahead

I thing we are generally more reserved, we don't usually stand up, waving our right fist in the air and making whooping sounds, everytime someone says something that we agree with!
To us, many things American seem bigger, louder, more 'in your face' and overly exaggerated - great for a 30 minute comedy show but you dont all live like that.........do you?

I suppose it's understandable, I mean we've got Cheddar Gorge and you've gone a tad bigger with the Grand Canyon