300 f4L stacking Teleconverters

Will the 300mm F4L accepted stacked teleconverters?

Either a Canon 2x plus 1.4x Kenko or

a Canon 1.4x plus Kenko 1.4x

thanks

If I remember correctly you can stack the TC's but you have some issues to deal with. I think only one of them will report to the camera, so that means your camera thinks you are losing one stop of light to the TC for instance when are losing much more. I'm pretty certain you also lose autofocus as well.

The reason you can't put the canon on some lenses it that it protrudes into the lens. If you go...
Lens...Canon TC... Kenko TC... Body
It should work.
But you will loose AF, 2 or 3 stops of light, and quite a bit of IQ.

Physically the Canons are the pain due to the protruding elements like mentioned. If going on a lens that can take them, put the Canon TC onto the lens first, and behind that put the Kenko TC as they fit basically anything.

As far as I'm aware only the TC directly on the lens will be recognised electronically, so if you put a 1.4x against the lens your combo should still try and AF. At F/8 on your 40D it will possibly work, less reliably, but with a 1.4x + 2x (F/11) it will be useless.

I wouldn't assume IQ will be poor. You'll just have very little light to cope with and so will need a steady platform, not to mention actually getting things in focus.

Romy Ocon's great Philippine Birds site has had a few references to stacking converters. Although, not necessarily using the 300mm f/4L IS lens...

http://www.pbase.com/l​iquidstone

i have stacked my canon 1.4x and canon 2x with the lens. it does get soft. it is better with just the 2x and crop the result.

I've stacked my 300 2.8 with both the 2X (mounted first) and the 1.4X. The lens info is transmitted incorrectly, but magnification is amazing. I did some live view manual focus shots of the moon earlier this year with both my 300 2.8 and my 100-400 (at 400). Being on a crop, I had good reach. Resolution stinks on this due to the re-size to post, but the original is quite sharp. This one was with the 300 with both TC's, and I expect you would get similar results with your 300 f/4.

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Both Sigma and Canon TCs have protruding elements so they only fit certain lenses and cannot be stacked. Tamron SP, Kenko Pro can be stacked. I did once take some Eagle pix with a 2x and 1.4x on the 300/4 L IS lens. Not too bad really. But not really a good idea.

richardfox wrote in post #11449457
I've stacked my 300 2.8 with both the 2X (mounted first) and the 1.4X. The lens info is transmitted incorrectly, but magnification is amazing. I did some live view manual focus shots of the moon earlier this year with both my 300 2.8 and my 100-400 (at 400). Being on a crop, I had good reach. Resolution stinks on this due to the re-size to post, but the original is quite sharp. This one was with the 300 with both TC's, and I expect you would get similar results with your 300 f/4.

I don't have a Canon 1.4x TC, but my understanding is that it's the same design as the Canon 2x TC (protruding elements). I don't think it's possible to stack two Canon TCs.

To the OP, why would you want to stack two 1.4x TCs instead of using a 2x TC?

The camerea will only see at most one TC. Using 2 1.4x's might give you AF where using a 2x will not.

lmans wrote in post #11440386
Will the 300mm F4L accepted stacked teleconverters?

Either a Canon 2x plus 1.4x Kenko or

a Canon 1.4x plus Kenko 1.4x

thanks

I used to stack the Kenko pro 1.4X and Canon 1.4X II with this lens to retain AF on my 20D. This worked OK at least in good light.

Test results here http://www.zen20934.ze​n.co.uk …00mm%20f4L%20IS​/index.htm
You have to click the menu links at the top to navigate in for the various test results.

However on the 7D the AF is all over the place, the 7D does have a bit more reach however due to the finer pixel spacing.

I would think there is a good chance it will be OK on your 40D however.

This was shot with Sigma 1.4 and 2X TC's on my 150-500 so that's 2240mm in old 35mm money I was focusing on the text on the box on my garage bench, probably about 70-80ft away I apologise for the cobwebs inside the window.

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Yes, you can stack the Canon 1.4X and 2X... You just need to put a 10mm or 12mm extension tube in between them.

Most of the big telephotos you might use in this way have enough extra focusing beyond infinity, you'll still be able to focus all the way to infinity.

I've done this - only very rarely - with 500/4.

Your viewfinder will be quite dim, AF will hunt badly if it doesn't fail completely, image quality will suffer and you had better have a rock solid tripod to keep everything steady, even with IS.

Just a quick correction Alan, you don't need a tube to stack the Canon 1.4xII and 2xII as long as the 2x is next to the lens.