Teleconverter Extender Stacking?

[MikeG104]

Recently got my Extender EF 2x III in the mail and loving what I can do with it. Out of morbid curiosity, is it possible to stack the extender with another 2x or the 1.4x for added multiplication of range? 

[deebatman316]

No its NOT possible to stack the EF 2x III only the older teleconverters can be stacked.

[johnruk]

Picking up this old thread.

Have tried this with R5 Mk 2 , 1.4x plus 2x and the rf 100-500.  Used 2  JJC extension tubes (16mm + 11mm) modified by making the mount big enough to take the extruding lens on the extenders, not difficult at all. it actually works reasonably well. It works best with the 1.4 at the camera end. The readings in the VF are meaningless but the metering works fine, As far as the AF goes, it needs to be focussed manually to be "close" but then in reasonable  daylight the AF works fine. I'm primarily interested in the moon and have yet to try it there but will upload results when I have something positive. Early tests look like the sharpness is about as good as you might expect, not brilliant but good enough to be post processed.

Hope this is of interest

[wq9nsc]

As you experiment, it will be interesting to see how cropping versus adding more extenders plays in terms of final image quality. 

I have a feeling stacking extenders may not compare well to more extreme cropping with modern cameras, even a single 1.4X has a noticeable impact on quality.

These are four images of the moon shot a few years ago and were captured with a 1DX III using in order: EF 800 f5.6 by itself, EF 800 with 1.4X, EF 800 with 2X, and camera mounted directly to Celestron CPC 1100HD optical tube (equivalent to a 2800mm f10 lens): https://rodgersingley.smugmug.com/Moon-EF-800-and-Celestron/n-ZHMxK5

Rodger

[normadel]

You can play around with stacking extenders but effective aperture will be reduced with each addition, to the point where the camera won't autofocus because of insufficient light, and your viewfinder will get dimmer making even manual focus more difficult.

Canon lens manuals tell if they work with extenders and point this out.