Extension Tubes Help

Burnrub

I bought a set of kenko extension tubes to use with my nikon D80.

When i use them tubes with any of my lenses, the camera can no longer focus at long distances, i.e "infinity".

is this supposed to happen?

i'd like to magnify objects that are both close and far away.

thanks.

Lord Vetinari

Yes I'm afraid that's normal.
Brian V.

pyry

Yeah, extensions move the entire focus range closer in - I don't think there's much help over focal length for things further away. I've seen dragonflies having their close-ups taken - in flight. The lens system used had a 1.4x TC, a full set of Kenko's extensions and a 2x TC stacked behind a 500mm f/4. Working distance was two or three meters if I remember correctly.

And since we're asking questions, I've got one I haven't found an answer to: Extension tubes cause the effective aperture to decrease, right? How would I go about calculating how much?

Lord Vetinari

pyry wrote:

And since we're asking questions, I've got one I haven't found an answer to: Extension tubes cause the effective aperture to decrease, right? How would I go about calculating how much?

Answers here might help http://photo.net/canon-eos-digital-camera-forum/00C0xN

pyry

Lord Vetinari wrote:

Answers here might help http://photo.net/canon-eos-digital-camera-forum/00C0xN

They do, thanks!

Burnrub

thanks guys, i wasn't sure if i was doing something wrong. the link to the photo.net discussion was especially helpful.