It sounds like quite a swipe...which lens is this?

I'd be looking at an insurance claim I think.

It should be smooth and easy to turn, so clearly something is amiss with your lens Brian.

Vic, I've done dozens of exhibitions, from Alexandra Palace to the NEC and others too numerous to think about. They are gruelling, and I've seen some exhibitors so exhausted that they cannot bear to even start a new conversation with a visitor.

My advice to any new exhibition staff is to forget the hotel bar, get some sleep. That will make life a lot easier for you! Oh, and drink lots of water.

You really need to have something specific in mind, give them a call and see what they can do.

It's still hard on the feet!

There are a number of 400mm primes that crop up now and again second hand, although many are quite rare. That step from 300mm to 400mm also means quite an increase in cost. The one most likely though is the Tokina 80-400mm AF zoom, which is good if stopped down but not exceptional.

Pentax have a 560mm prime which is not expensive compared to other marques, but still pricey enough for most of us. Also upcoming is the new 150-450mm zoom.

I'm waiting for the 150-450mm and just hope it will at some point be affordable!

Thinking of numbers, we know that DSLR sales outnumber sales of EVF cameras by many, many times. So I think this reason is unlikely. There are probably just very few photographers who now want to use old manual focus lenses and of those even fewer who think of changing the focusing screen. These numbers will probably get less and less as time goes by, and maybe the number has already fallen below a figure that makes the business sustainable.

At the moment prices do seem very low. Like Mike says, unless it's a rare or very desirable item.

Cosina were really a low cost lens manufacturer, some lenses being better than others. I'd much prefer the Pentax 24mm f/2.8 if you can fine one.

I understand Louise, but I'm sure that once you get there you'll find it's manageable. If you miss something, so be it, there's plenty more to see!