Stacking FD extension tubes

[mark_pierlot]

I'm wondering whether FD extension tubes (the ones that have an aperture lever, etc.) can be stacked. I have an FD

25 and an FD 50 tube. I know that the mechanism-free tubes can be stacked, but it would be nice to have 75mm of

macro extension and retain functionality.

[daniel_kim7]

I have stacked FL 14mm extention tube with a FD 25U and it does work functionally. It decreases the minimal focusing distance. Hope this helps. Daniel.

[ben_hutcherson]

Yes, you can stack tubes, provided that you don't exceed two tubes, or other accesories(I believe). The reason for the limit is that's beyond this, the mechanisms start getting too sloppy to allow reliable coupling.

[gordon_yee]

Canon advised against stacking the FD series of extension tubes. The concern is that the amount of force needed to close the lens' diaphragm may stress the camera's aperture coupling lever and increase the wear-and-tear. If you stack two FD extension tubes, the camera's aperture coupling lever must move the combined mass of three aperture levers, as well as overcoming the friction between them. I suspect that it could also affect the camera's ability to stop the lens down consistently.

 

I'm sure some users have stacked FD extension tubes with no apparent problems, and that Canon may have been conservative in their recommendations. Just be aware of Canon's position and proceed with care. If you're using a body that has the stop-down feature, you may want to use it to reduce the stress on the coupling lever.

[awahlster]

I have used both a FD-15 tube and 2X-A many times with my 500mm f4.5L S.S.C. but as said it can both add weight and resistance to the mech. which can cause both wear and the possibility of the lens not stopping down in time for the exposure.

[jeffrey_e]

I wouldn't due to the stress on the camera. I suggest that you consider getting an autobellows and leave off stacking extension tubes..

[philip_wilson]

I occasionally use the 25U and 50U stacked on my 100mm F4 and have had no problems. I do however manually stop down the lens which may help. I have used this setup mainly on F1Ns and occasionally on the T90 for quite a few years. I think if you avoid using an automatic mode little damage will result.