Couple of questions:

Is there a fixed relationship between an extension tube and the lens you're using it with. i.e. If I stick a 10mm extension tube onto a 50mm lens does it alter the total focal length of the lens? If not what does it alter? I know that less light will hit the sensor.

If the lens were a zoom lens would the relationship be linear?

How do 'speed boosters' work. How can sticking an extra element in between a lens and a sensor increase the aperture of that lens? This I do not understand at all

Try these links speed booster > http://www.slrlounge.com/near-full-frame-in-a-micro-43-camera-the-metabones-speedbooster-nikon-adapter-review/

Extension tubes> http://www.discoverdigitalphotography.com/2013/macro-close-up-photography-using-extension-tubes-bellows/

Hope this helps

Cheers fim. I understood the speed booster straight away but the extension tube explanation is going to take a bit of re-reading :-)

Supplementary question. Which is better for a cheapskate macro facility. Extension tubes with all the contacts for AF etc. or a Raynox DC150 or 250?

Supplementary question. Which is better for a cheapskate macro facility. Extension tubes with all the contacts for AF etc. or a Raynox DC150 or 250?

I'd go with Raynox 150 if on a macro lens, 250 if on a non-macro lens.

These are good. I'm after one for my Pentax D-FA 100/2.8 WR. Also look at Zerene Stacker.

Cheers MJP. You just led me onto this site which looks really interesting to me.

http://extreme-macro.co.uk/raynox-adapter-techniques/

PS. 'The Gang' are still on my desktop :-)

Cheers MJP. You just led me onto this site which looks really interesting to me.

http://extreme-macro.co.uk/raynox-adapter-techniques/

PS. 'The Gang' are still on my desktop :-)

If you need a new desktop just let me know.

While the question is being asked, I would also like to add, are close up filters any good for the purpose of getting a shorter minimum focusing distance?

Drawbacks if any?

I have never even heard of speed boosters cheers for bringing the subject up it up and for the links others have posted.

Cheers MJP. You just led me onto this site which looks really interesting to me.

http://extreme-macro.co.uk/raynox-adapter-techniques/

PS. 'The Gang' are still on my desktop :-)

If you need a new desktop just let me know.

I will but I must admit they always make me smile whenever I see them. Thailand's Bugsy Malone

Cheers MJP. You just led me onto this site which looks really interesting to me.

http://extreme-macro.co.uk/raynox-adapter-techniques/

PS. 'The Gang' are still on my desktop :-)

If you need a new desktop just let me know.

I will but I must admit they always make me smile whenever I see them. Thailand's Bugsy Malone