Extension rings-HELP

Flora · #1 (**permalink**) 27-12-2006, 08:20 PM

Hi all!
I need some advice please and don't want to go into a shop and look a complete prat, so I'd rather ask here where no-one can see me!
My husband bought me a set of extension rings for Christmas pressie. I thought they would magnify the image so that I wouldn't need to get so close to an object.
I realise I have to manually focus as auto focus doesn't always work with them attached but they stop me taking pics altogether.
Do they work on all lens no matter what the size of the lens?
The ones I have are 13mm, 21mm and 31mm. I have tried them on all the lenses I have but I can't focus with them and the shutter relase button won't depress.
They are for the Canon 300D
Any help or advice will be gratefully received (but keep it simple please)

wildlifesnapper · #2 (**permalink**) 27-12-2006, 09:02 PM

Hi,
it sounds as if you are getting extention rings mixed up with tele-converters.
It's tele-converters that magnify the image so you don't have to get as close,i.e if you focus on a bird at fifteen feet away then fit a 2x converter the bird will be twice as big in the frame at the same fifteen feet.

Extention rings allow the lens to focus closer i.e if you put an extension ring on a 100mm lens you will probably only be able to focus up to 12-15 inches away from the lens.You won't be able to focus at say 3 feet or infinity.They are generally used for macro work on small insects of flowers etc instead of or with a macro lens.
They will work with any lens but the distance you can focus depends on the focal length of the lens so 100mm lens say will focus to 15 inches and a 300mm lens probably to 4 feet and no further(a guess,never tried it on a 300).
As for the shutter,are you using the camera on an automatic setting or in autofocus so the camera wont take a photo unless the lens is in focus?
Try putting the camera on aperture priority (AV) and find the focus range of the lens with extension tubes fitted (try around a foot) and it should take a photo.

Hope this helps
Neil