Overall though may it not be cheaper? There are no costs involved in shooting a digital image (unless we count the cost of charging the battery...)and we shoot a lot more images.

When upgrading, the outlay is mitigated by whatever we sell the existing camera for.

I'm not saying there is no cost, but it might not be all that great and would certainly be less than the cost of using as much film as we use digital.

Without resorting to even trying to think round your mathematics, focal length can change with focusing distance, and mostly does with imperfect lenses.

Your magnification might be easier to think of as about 1:3, which is actually usefully close and better than the 1:4 that is common to standard zoom lenses.

I'd spend more time taking images aas well. If you really want to go into the maths of lenses, then there are books on optics that will more than whet your appetite.

Somebody has too much time on their hands....

Nice images, I'll pop them into the Your Photos section.

When Pentax have such a cracking good 55-300mm lens, even in a low cost DA-L version if needed, why would we be interested in a Tamron with a reduced range?

It's interesting how quickly though the mood swings from "Pentax are too slow and lag behind the market" to "Pentax are too quick to bring out new models" - it's hard to see what speed would suit everyone!

Like every other organisation they go when they're ready, and no doubt at the last minute everyone is running around like crazy to get things together on time. Dealsines do get put back when needed, but there comes a time when the button has to be pressed.

That applies to buyers as well. We can wait and wait and wait....but while we are waiting someone else has been enjoying a very fine piece of kit.

A hood is also not the best protection when faced with salt spray, but we are talking about general situations.

I have never had a Pentax bayonet lens hood that has been loose, fallen off or been anything else but solid.

Also, the lens hoods that are plastic will absorb impact up to a point without damage. A metal rim filter has no give, so will transmit all the impact to the lens.

However, this is all very clumsy and I do not routinely expect any impacts at all. In fact, so far in several decades there haven't been any.

You will get much better atmosphere without flash, so that's a good choice. Don't forget that sometimes swirling dancers with lots of coloured lighting can look pretty good, so maybe don't try to stop the action all the time.

The 35mm f2.4 should be quite versatile, just up the ISO setting with confidence. I'd try ISO3200 to start with and then just go higher if it's needed.

You may need to switch to manual focus if the light is very low, but leave the camera on Av and select a wide or open aperture as a starting point.

Here's a far fetched one - you have the camera set to remote release and every time someone uses the TV remote, the camera fires....that would be a really hard to fathom fault.