A question on extenders.. and it is only mildy stupid!

After reading a lot of discussion on the Canon 1.4x and 2x extenders, it seems that there is a pretty good consensus that the 1.4x is fantastically sharp, while the 2x is slightly less than. I am wondering about using 2 1.4x's instead of a 2x, and am not sure whether this is a good idea. Since the 1.4x loses 1/2 stop, 2 of them would be the same light loss as a 2x extender, and the additional focal lenght is neartly the same. I am wondering whether the additional glass would degrade the image more than the 2x would. Does anyone have experience with this combination?
(I initialy thought of this for use with the 200 1.8L, which i considered buying for about 3 minutes, and then realized i can get a solid new computer and some AB strobes for the same price..)

EDIT-- i just realized i spelled "mildly" wrong in the title.. so ill downgrade this from mildy to fully stupid question

Here's an example thread of two 1.4's stacked on a 100-400 IS. Very, very good.

https://photography-on-the.net/forum/showthre​ad.php?t=256732

Mr. Clean wrote in post #2586095
Here's an example thread of two 1.4's stacked on a 100-400 IS. Very, very good.

https://photography-on-the.net/forum/showthre​ad.php?t=256732

Yes indeed! Very nice image!

WHOA! what a great idea- doubling 1.4x extenders on a 70-200 would give some great reach for much less than buying a 500mm lens.

has anyone tried it?

Keep in mind that you cannot physically stack two Canon 1.4 extenders together. The example from the link used a Kenko Pro 1.4 and a Tamron 1.4.
The Canon's have an element that sticks out into the lens that you are fitting it to.

Just a quick not to clear up a bit of confusion (for me anyway)

I think you are refering to Tele-Converters (TC's) not extenders which are a different proposition.

If so then I can recommend the Kenko Pro300 DG 1.4
With two stacked the lens would be MF only.

evandavies wrote in post #2586740
Just a quick not to clear up a bit of confusion (for me anyway)

I think you are refering to Tele-Converters (TC's) not extenders which are a different proposition.

If so then I can recommend the Kenko Pro300 DG 1.4
With two stacked the lens would be MF only.

Youre right, i meant TC. I was reading a post right before i started this thread that was talking about extensions, and the word must have stuck in my head.

evandavies wrote in post #2586740
Just a quick not to clear up a bit of confusion (for me anyway)

I think you are refering to Tele-Converters (TC's) not extenders which are a different proposition.

If so then I can recommend the Kenko Pro300 DG 1.4
With two stacked the lens would be MF only.

"Extender" and "teleconverter" are normally used synonymously. In fact, I believe "extender" is Canon's "official" terminology.

Extenders == TCs = Converters
Extensions == Extension Tubes == Tubes

From Canon's website:

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Nicely Done Runninmann

RNeudorf wrote in post #2586711
Keep in mind that you cannot physically stack two Canon 1.4 extenders together. The example from the link used a Kenko Pro 1.4 and a Tamron 1.4.
The Canon's have an element that sticks out into the lens that you are fitting it to.

I remember reading somewhere that a 2x could be coupled with a 1.4x (both canon), so I just assumed that two 1.4's would work in the same way. I did once try jevidon's Canon 1.4x with my Sigma 1.4x, and slapped on 3 Kenko tubes behind my Sigma 180 macro, and that thing was a monterous hulk of incredibely-hard-to-focus glass, but the Sigma and Canon did not want to fit together directly (extension tubes were between them).