Extension Tubes

I've been thinking for a while about doing some macro photography and was looking at a macro lens but after seeing David Storm's macro with extension tubes I thought I might investigate that avenue. I'm a bit confused with these
http://www.ebay.co.uk/itm/Rare-Pentax-KA-fit-Extension-Tubes-Set-with-electrical...

If all the electrical contacts are there - how come they are still manual focus? Do they simply allow aperture control?

It allows full auto aperture control and full metering/mode capability.

Manual focus because there's no AF drive connection provided.

They are the ones you want, if you are using a Pentax A lens at about 50mm you'll get some fab results. However, this set is missing a tube, they usually are 13mm, 21mm and 31mm and a price of £69 is what I'd expect to pay for a full set

If you look carefully at the photo you will notice that there is no little drive slot(or drive pin to go into a drive slot) to take the drive from a camera. they have the connections for aperture etc but no mechanical connection for AF.
CHEERS Vic.
PS. John you beat me to it. Vic.

I don't think there is a set of tubes with AF for Pentax, besides the last thing you need is AF when using tubes as the target is so small i.e. an insects eye. Besides Pentax have a much more useful feature when getting in this close and that is Catch in Focus. Awesome function

Would these be a better purchase as I'd intend to use them with some legacy lenses Pentax M 28mm f2.8, M 35mm f2.8, A 28mm f2.8 and A 50mm f2 ?

http://www.ebay.co.uk/itm/PENTAX-PK-fit-EXTENSION-TUBE-SET-pentax-/380807124903?...

Thanks

No, there are no electronic contacts.

69 quid is a rip-off. I paid thirty and they came with an MZ-30. Extension tubes with electrical contacts are not very rare and it shouldn't be hard to find a full set for half that price.

Even cheaper would be a macro reversing ring if you have a good, manual 28 or 35mm lens.

These do come up in the classifieds on here from time to time, so keep an eye out. If you can get them for as low as £30 (like Jonathan-Mac did) then I think you'll have a bargain - they usually go for between £50-60ish. I have a spare set with electrical contacts that I am currently modifying (removing the black paint ) and will list in the next couple of weeks if you can wait - but they won't be less than £50

If you don't mind an old-fashioned approach, and if you're using a lens with aperture ring, you could do what I did - set of three Vivitar extension tubes bought from West End Cameras on Tottenham Court Road in mint condition for the princely sum of £5 incl caps......

Thanks for the responses.

Whilst trawling for detail on extension tubes I'd read somewhere that adapting old converters allows them to act as extension tubes. My son had given me an old K fit Hanimex X2 converter so I thought I'd play with that. Ten minutes later I had de-glassed it. It measures 25mm from flange face to flange face. With that and my 50mm f2 lens I appear to have a 1:2 macro, and with my 28mm f2.8 an almost 1:1 macro. The only issue is the close object distance. I found this site which is informative regarding extension tube use and calculation of image size/ratio.

http://www.mystd.de/album/calculator/

If you get the Jessops extension tubes with contacts be sure to scrape off some of the anodising on each tube to complete the electrical circuit. The body of tubes is the return path