Stacking Canon Teleconverters

Grimace said:

Hey gang, I wondered if anyone has ever stacked two 1.4x teleconverters to get closer to the 2.0x version. It would only be 1.96x but that's close enough!

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I do know that there are some photog's that have stacked...I think it was a teleconverter with an extension tube? And maybe then another teleconverter...perhaps a non-Canon so that AF will still work?

Might have been some experimentation done by John Shaw, but don't quote me on it.

The 1.4x has far better performance than the 2.0x but I wasn't sure if two of them would fare any better. The other benefit is that one could use a 1.4x converter on two different lenses, or stack them when needed.

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A stack of two 1.4's will always fare worse than a single 2.0 ... it just makes sense that this is so, because if it wasn't worse, then the design of a 2.0 could just be two 1.4's internally (close enough). And it doesn't really do you all that much good to have two of the same item...better to have a 2 and a 1.4, particularly if they can be stacked with reasonable results.


-hh

the magnification difference is trivial.. .196 vs .200

Image quality should suffer pretty good. Aperture might take more of a hit than a 2x though regardless of the math.. f4 x 1.4 = f5.6 / f5.6 x 1.4 = f7.84 - But honestly, I'd put the affective aperture around f11 or so.. You can test it to see though once you've couple it all together. Using same shutter, metering mode, etc, put your lens with no tele's at f11 and take a shot, slap the couplers on with the lens f-stop to f4 and take a shot, compare the two for an idea as to what f-stop your minimum is.

You did know that when you multiply the focal length using a teleconverter, you're also multiplying the aperture as well, right