You have a potentially excellent lens that sounds as if it is very worn and poor condition. Focusing on Pentax lenses should be as smooth as silk, but not loose and sloppy. Although some very long lenses are designed to focus beyond infinity, usually mirror types that need to be able to compensate for dimensional changes due to temperature, 35-70mm lenses are not.

If you can find one, I have a preference for the SMC Pentax-A 35-70mm f4, not because of quality issues but because it has a fixed aperture throughout the zooming range. This is useful for flash calculations, and for manual matering.

There are a number of 35-70mm zooms, the most useful being the SMC Pentax-A 35-70mm f4 in my opinion. This is because it has a constant aperture value over the zooming range and continuous focusing down to a very useful 1:4 magnification at 70mm.

All the 35-70mm lenses should be sharp, crisp optics and if you have a "muddy" one, then perhaps an element is loose or misaligned or the lens has been subject to some sort of damage.

Front of lens converters gather light from a wider angle and project it through the camera lens. Telephoto converters are also available.

IMHO there is nothing dangerous about eBay providing you take sensible precautions and know what you are bidding for. Check sellers feedback carefully. No seller wants negative feedback, so most transactions will be fine. Don't forget that eBay is now a European company as far as we here are concerned.

Most manufacturers offer lenses for amateur use at low cost and other ranges for professional use at usually much higher cost. These more expensive lenses may have more glass, different glass types, wider apertures, more substantial manufacturing and so on. You do get what you pay for, but some cheaper lenses can be remarkably good as they are made in huge qualtities and this brings down the unit cost. They may not take the knocks so well, but the results could be indistinguishable from much more expensive optics.

I can't comment on the 75-300mm lens, but I expect Pentax lenses to be of a good standard. As regards a fisheye, you can get the result very cheaply by buying a fisheye converter, which is an auxiliary lens that fits into the filter thread of your main lens. With a 28mm it gives a fisheye effect. With a zoom set at 28mm it may not be so satisfactory as with a prime 28mm, but a second hand one might not be too expensive and could be worth a try. At least you could experiment with the effect before buying something better.
For second hand lenses eBay can be a good choice, but you need to buy carefully. I have had some superb lenses from eBay and sometimes some less than good ones, but at least the price has been modest.
The *istD is one of the best digital SLRs and an obvious choice if you already have Pentax lenses. The price seems to be moving slowly downwards. I am taking a wait and see stance, but I will buy when the price excites me!

I think the lens sounds as if it is a goner, so there could be nothing to lose by opening it up and having a look! I tried it once and ended up with an interesting asortment of mysterious pieces of metal, screws and sundry items of indeterminate function.......

But you might have more skill and/or luck that me!

We haven't really had any problems with memory cards, but two things come to mind. Have you tried formatting the card in camera? Have you tried formatting the card on a PC using a card reader? If the card has been used in another make of camera that can sometimes cause problems. Finally, some cards do not work well with some cameras and maybe a different make of card will be needed.

Kevin, seeing you live almost next door to me (Tyldesley) would you care to come along to our Photo Society in Atherton? We're very active in all aspects of photography and there is no obligation whatever to join immediately. You would be most welcome to come along and see what we are up to. Meetings are on thursday nights at 8pm and our Summer syllabus is well under way.

The details can be found at www.adaps.org.uk or by all means e-mail me directly.

Personally, I don't object to "ads" in the forum, but I do think they should be between friends, so to speak. In other words, between registered members exchanging useful infornmation.

For example, I have been searching for a mint SMC Pentax-A 35-70mm f4 lens for some while. I have now found one, but an enquiry on this forum could have found one sooner! I don't think that sort of buying/selling would be a problem.

Any other opinions out there?

If certain posts are to be banned, then the forum will probably need to be moderated, but I'm sure Peter Bargh will be watching the situation closely.

For all practical purposes, DIN is the same as the logarithmic speed given currently on all film boxes. So 400/27 ISO is the same as 400 ASA or 27 DIN.

Kim is quite right in that if you add 3 to the DIN value you will double its ASA or the first ISO number. So 800 ASA we can calculate as being 30 DIN.