Extension Tubes for FD mount on GH1

[exttreem]

Hi, I found many Extension Tubes for FD mount and they are available in 6mm, 12mm, 24mm, 50mm, etc.

What exactly these numbers mean? How much magnification do I get if I put each of them on my 135mm FD or 70-210mm FD?

And which one should I buy?
The one which is very Cheap? such as this...
http://cgi.ebay.com/MACRO-EXTENSION-TUBE-SET-CANON-AE-1-PROGRAM-A1-FD-/190470156961?pt=LH_DefaultDomain_0&hash=item2c58e7f2a1

or The one very expensive?
http://cgi.ebay.com/Canon-FD-Extension-Tube-FD-50-Mint-w-case-/250728693530?pt=Camera_Lenses&hash=item3a60983f1a

What is the Difference?

[sam rides a mtb]

I use a 25mm FD extension tube seen here:

26037

I will use it on my 50mm 1.4 more than the 100mm f2 in that photo.

Really lets me get the camera a lot closer for macro shots. though must be removed for anything that is not within macro distance as it won't otherwise focus.

there are some samples from f2 to f32 at:
http://www.flickr.com/photos/sol_rider/sets/72157624687204126/

i think you can add tubes together, so it might be worth getting a couple smaller ones, rather than one large one - i found 1 25mm tube to be enough

edit: also, try to get the actual canon one - found mine in new condition for about $25

[photoSmart42]

Hi, I found many Extension Tubes for FD mount and they are available in 6mm, 12mm, 24mm, 50mm, etc.

What exactly these numbers mean?

The numbers are quite simply put the depth of the tubes themselves. The 6mm tube is... 6mm tall. etc.


How much magnification do I get if I put each of them on my 135mm FD or 70-210mm FD?

The relative magnification you get with each tube depends on the lens focal length you use. The formula is: Total extension used / Focal length used = Magnification. You get more magnification when using lower focal lengths than you do with longer ones.



And which one should I buy?
The one which is very Cheap? such as this...
http://cgi.ebay.com/MACRO-EXTENSION-TUBE-SET-CANON-AE-1-PROGRAM-A1-FD-/190470156961?pt=LH_DefaultDomain_0&hash=item2c58e7f2a1

or The one very expensive?
http://cgi.ebay.com/Canon-FD-Extension-Tube-FD-50-Mint-w-case-/250728693530?pt=Camera_Lenses&hash=item3a60983f1a

What is the Difference?

Buy the cheap one. The expensive one is someone's bad joke for trying to sell some extension tubes as collectors' items. If you just want to use them and not keep them in a glass case in a museum, get the cheap ones. They'll do the same job.

[exttreem]

The relative magnification you get with each tube depends on the lens focal length you use. The formula is: Total extension used / Focal length used = Magnification. You get more magnification when using lower focal lengths than you do with longer ones.
OK, so how can I get 2x magnification on any Focal Length? i.e. can 210mm become 420mm?


... The expensive one is someone's bad joke for trying to sell some extension tubes as collectors' items. If you just want to use them and not keep them in a glass case in a museum, get the cheap ones. They'll do the same job.
Well Said... Thanks! :)