What functions do you lose with ext tubes?

[Grumby]

I'm looking at getting some (cheap) extension tubes for my D40x and kit lenses (as described below - the 55-200 is a VR model), but I gather that without a means of continuing the electrical connections from body to lens, there will be some functionality lost... Is anyone able to qualify this?

My guesses are

• no autofocus
• no aperture control (no aperture rings on my lenses)
• no vibration reduction (where this is in the lens rather than the sensor)

If I have no aperture control - does that mean all photos will be taken with max aperture?

Does anyone know if Nikon make a set of tubes that DOES continue the circuitry, and therefore eliminates the issues?

Cheers,
Grumby


Additional:
Just did a bit of legwork during lunch...
Local camera shop (Ted's) only sells a Kenko kit, which supports autofocus (not sure about other functionality), and costs AU$300
ebay has same kit available for about $175
ebay also has numerous 'cheapos' for around $20-50 which have no electrical pass through.

Additional additional:
Is it just the electrical connections between those contacts on the body and lens that need maintaining? I remember on my old Praktica SLR, there was a little thingy in the body that pushed against a little pin in the lens, that caused the iris to shut down when you triggered the shutter - but I guess that is all electronic these days...

I was wondering if I bought a cheapo set of tubes, and then hacked the Nikon specific mount parts by letting a small section of veroboard into each of them (carefully lined up with the contacts, obviously), and then ran a ribbon cable between the two (externally, so that I can still change the configuration of the tubes between the mounts), whether I could cobble together a cheap but fully AF compatible set of tubes? It seems that a hike from $20 to $300 is an awful lot just to provide 4 or 5 electrical connections between each tube!

[inkista]

I'm a Canon shooter, so you'll want to back up what I say with a little research.

Nikon's tubes are probably the most expensive (each of the three is about $85). Kenko makes a set with contacts ($170-$180). But the best price I've seen is probably for the Pro Optic set, at Adorama ($90 for the set). That listing looks a little weird--you might want to call and find out if it's the set with the metal mounts or the set with the plastic mounts (on the Canon side, the $90 set has metal mounts, the $60 set is called "budget" has plastic mounts).

You also need to be aware that when you use extension tubes, you lose the ability to focus to infinity. Typically, depending on how much extension you add, the combination will only focus at a given distance from the subject, so you won't have much choice on framing. This is why a macro lens is still worth the money.