We're not supposed to, I'll have a look now. The point is that there should be no influence, albeit unintentional, on the judging.

There's no point speculating as no-one actually knows apart from the forward planners at Pentax...however, take heart from their excellent record on backwards compatibility.

An extension tube does not alter the focal length of a lens, it just enables it to focus closer. It has no effect on the speed of the lens or its quality, but because of the extra extension the tube causes there will be some light fall off and exposures will need to be increased.

In fact all lenses lose a bit of light in this way, but the close focus is usually made at a point before this becomes a real factor. That is why in prime lenses minimum fous distances can be related to the focal length. 50mm lens, around 50cm (actually 45cm usually), 35mm lens around 30cm, 100mm lens around 100cm, and so on.

You'd be better off asking HMRC. They probebly have a helpline of personal importing, or something on their website.

It would have to flash after the shutter was partly closed, but the exposure difference would be a sharp edge.

Shutters can of course "taper" - slowing down as they reach the end of their travel. They can also bounce back slightly instead of closing properly, but this can easily be tested by using just one flash, or even the built in flash, to establish that the shutter gives an even exposure.

With the speed of light being what it is, there is no way that any one flash could fire early. They flash simultaneously when the shutter is open. If the synch was wrong it would be the camera that simply closed the circuit at the wrong time and that would affect all flash units.

Just to clarify, the DA* lenses are "dust-proof and water resistant" and the 18-55mm WR and 50-200mm WR have a "simplified water-resistant contruction".

In practice, the latter worked extremely well and the use of a lens hood prevented splashes on the front element. A filter would put a glass surface in a more exposed position relative to the lens hood and would probably make it vulnerable to splashes.

The pentax 50-135mm is the better lens and has a reasonably fast maximum aperture, so I'd tend towards that.

The low light use probably excludes the otherwise excellent 55-300mm DA lens.

There is also the Asahi Pentax Manual (Morgan Publishing, 1971) which is a huge loose leaf ring binder affair that covers all the bodies and lenses up to that time in great detail.

I had no idea my pristine copy of the Screwmount Guide might be worth £400!!!

Life wasn't so varied in 1962-64 as it is now. The Pentax Spotmatic with built in TTL meter arrived in 1964 and was with us until around 1975 when the K2, KX and KM cameras were introduced. Even then, the KM was basically a Spotmatic with bayonet mount.

So you will be looking for a Spotmatic or, from 1970-ish, Spotmatic II and that's your lot in Pentax TTL metering screw-thread cameras! Purists will mention the SP500 and SP1000, but those came much later and don't fit you time requirement.