stupid lens/extension tube question

if i got an canon or kenko extension tube, is it possible to put a EF-S lens on the tube and then put the tube on a full frame (EF only) body ?

i want to get the 10-22mm EFS soon and also want some extension tubes
if i can use the tubes to put the EFS lenses on my old Eos 300 body it would be great, using a 10mm lens with 35mm film body.

it won't focus to infinity if it does work, sooo err that'll rule out landscape and most stuff

#1. kenko tubes dont fit EF-S lenses, but canon ones do.
#2. the lens wouldnt focus to infinity anymore, so that would rule out most all purposes for the lens.

Just curious. What's the purpose of using tubes on an ultra wide? I have both but have never stacked them together. I figure with tubes, the subject would have to touch the front element of the ultra wide in order to achieve focus. No?

yes i belive that even with a short tube, in order to obtain the correct focus, the point would actually be somewhere behind the front element. the cool upshot of this being that you can focus on the dust in the front of your lens . i really think i saw someone do that.

thanks for the help guys, i dont really have a reason for asking, i was just curious
i was looking at the 10-22 EFS yesterday and i really want one, and i am going to get either an extension tube or close up filters for my lenses
i was just wondering if i switched to a full frame camera later would i be able to use my EFS lenses on it
i now know that i could, but there wouldnt be much point as they wouldnt focus to infinity anymore.

cfcRebel wrote:
Just curious. What's the purpose of using tubes on an ultra wide? I have both but have never stacked them together. I figure with tubes, the subject would have to touch the front element of the ultra wide in order to achieve focus. No?

The Magnification = extension / focal length. So if you want the highest possible magnification of a subject, you put a SHORTER focal length on a tube. For example, 25mm tube on a 100mm lens = 0.25x highest mag. But 25mm tube on a 12mm lens = 2x mag!

yes but the problem is that a 25mm tube on a 12mm lens would also put the focus point needed to gain focus INSIDE of the lens, rendering the whole thing useless.

Yup I heard tubes only work with 50mm+ lenses so it wouldn't work.

To be honest I'd get the EF-S 10-22 and worry about going FF when it happens, could be years off! just sell and get the 17-40mm or similar if you do...

Where are you coming up with that?!

Subject is in front of the lens' front nodal point; the lens is always focused on a point behind the rear lens nodal point. The magnification is determined by the ratio of front-node-to-subject : rear node to focal plane. If you move the lens farther from the sensor with the tube, the subject can be closer to the front node.

I will admit to not being an optical engineer, but it sounds rather bizarre that tube could ever cause the subject to need to be placed inside the lens in order for it to be in focus! Tell you what...when I am home this weekend, I will take my Canon 10-22 and manually hold the lens out one inch (25mm) from the body and see if I cannot get close enough to the subject (i.e. needing the subject to be inside the lens)...I bet not. Macro bellows extensions have been putting short focal length lens out long distances, at far greater multiples than their focal length, and have been taking high mag macro photos since forever with the circumstance which you think would be impossible.

The instructions for my 17-40L say that at 17mm the lens is incompatible with the 25mm extension tube. I believe this is because of this problem, where the working distance reaches zero. It can't be for any physical internal clearance reasons, as it is ok with the 12mm tube. It is also fine with the 25mm tube at 40mm. I don't have any tubes, so I can't do the experiment.

isn't that kenko extension tube will mostly benefit for Macro shot?

Interesting, the 'not compatible with 25mm tube' categorization! I don't have tubes for EF, either, but I was just going position the lens manually to see if the subject distance issue arises. Again, I point to very long bellows and short focal length lenses having been around since forever for macro work, so why not the short Canon lenses on long extension?!?!?!

with the 25mm extenstion tube on my 17-40 at 17mm i cannot achieve focus on anything, even touching the front of my filter. not even close infact.

correct, at 17mm it is all a blur, but as you zoom out toward 40 you can achieve focus. even with the 12mm, at 17mm the subject has to be almost touching the lens to get focus, it has to be much worse on the 10mm.