Beginner Kenko [Canon] Extension Tube C/AF not DG

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Just bought a set of these tubes, described as "Set of 3 kenko Canon EF extension tubes 12mm 20mm 36mm For Digital SLR". Can't get any of my EF-S lenses to fit on them.
Are these tubes actually meant for Canon EF Digital SLRs? Have they been misdescribed or have made a cock-up and bought the wrong thing?

Thanks for any help
 
Are they the ones with the rectangular aperture through the tube or the round one?
 
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These are two (ostensibly identical) Canon EF extension tubes.

The one with the round aperture works for every EF-S lens I've tried. The one with the rectangular fouls the protruding rear element of EF-S)
 
How is it not fitting then? Is it the rear element of the EF-S lens fouling the tube or is it not clipping in?

Remember the EF-S registration mark (white square) is offset approx 20° clockwise (looking down the barrel of the lens from the front) to the EF registration mark (red dot)
 
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Whether the clip on extension tubes is forward or pulled back, Turnig the lens in the front of the extension, at no point does
the lens slip in. It's if the extension diameter is too small. I would say there's always a 2mm gap between the two.

Correction. The lens does slip in a little, but there's still that 2mm gap. Also there's only a red alignment dot, not a white one.

Thanks
 
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My hunch then is that the protruding rear of the EF-S lens is being fouled by the instepped element in the tube (thus the tubes are not suitable for all EF-S lenses) - can you see this if you look into the open end of the tube, perhaps?

The absence of the white square EF-S registration mark isn't 100% indicative but it is suggestive of this. That said it doesn't have to be there for it to work (my Canon tubes don't have it, but still allow use of EF-S lenses - at least all that I have here to try...)
 
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"being fouled by the instepped element in the tube". Not sure what that is? What I can say though, the depth of the internal extension face where the extension and lens meet is about 2mm shallow for the efs lenes. Oh well, Kenko extension tube set [used] for £20 - perhaps that's to be expected.

Thanks
 
Follow up. Here https://www.dpreview.com/forums/thread/3055040 I found.

There are two distinct versions of these tubes. On the 36mm tube, you will see either "for C/AF" or "for C/AFs". The ones that say "for C/AF" do not support the Canon EF-S mount. They support only the EF mount. If any of your lenses are EF-S, then you will need the ones that say "for C/AFs". Functionally, they are equivalent, but the "C/AFs" models can mount both types of lenses. As of now, it is impossible for me to tell which version is being sold here. I have to assume that they are selling the "C/AFs" model.

So that means I need to look for the C/AFs model
Click to expand...
 
Another follow up. I’ve found some other examples of the same modal extension rings for sale online. The description for those all say NOT FOR EF-S LENSES.
 
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