New lens... err body?

[wickidwombat]

Howdy I have the kenko C-AF 1.4X teleplus pro 300DGX it works with all lenses fully translates the aperture I used it for ages on a 28-300 L and it is awesome (I since sold that lens and got a 300f4L IS instead, some softening of the image wide open but drop it 1 stop in good light and iq is still awesome. I've tested it on all my lenses even works on the 16-35 not that i actually use that combo but it does work really nicely with the 50mm f1.4 and gives very sharp f2 images

 

[K-amps]

For birds, I'd definitely take the 7D over the 5Dc with the 70-300 L.

What lens were you planning to get to use with the 2x TC? Your 70-300 L cannot take a Canon TC.

I read a review that it takes the Mk. III converters. The guy shot some pics with the 2x Mk. III

Ahhh the Internet, fountain of Truth. :

The source was: Shutterbug Magazine.

Aug 2011 issue

The reviewer was Farace or something IIRC.

Edit: found it on the "internet" too. Here's the URL for it:http://www.shutterbug.com/content/canon-ef-70-300mm-f4-56l-usm-long-short-it

 

[neuroanatomist]

Thanks for the link. I agree with the one comment posted to the review - that was a pretty bad misrepresentation. As Dr. Croubie points out, the rear element of the lens is right at the back. I think he mis-typed when stating it's at 300mm - I think it's at 70mm and the rear element moves further 'in' (away from the lens mount) as you zoom to 300mm - at least, that's how most extending zooms behave (except the 24-70mm which uses a reversed design). So, it's 'compatible' at longer focal lengths, but not 'compatible' (= lens damage) at shorter focal lengths.

 

[dr croubie]

...I think he mis-typed when stating it's at 300mm - I think it's at 70mm and the rear element moves further 'in' (away from the lens mount) as you zoom to 300mm - at least, that's how most extending zooms behave...

Well, yes and no.
a) I'm bored.
b) It just started raining so i've got nothing better to do than take photos inside.
c) I just got my first-ever speedlite in the post from ebay (a 430EXmk1) that I wanted to try out, i put it on the floor pointing at the rear element to reflect to make it easier to see.
d) The 70-300L is not a "normal" design, it's got 'floating elements' all over the place. At 70mm, the difference between macro and infinity is not much. Leave the focus at macro and zoom to 300mm, the rear element will come out a bit (200mm or so) then go back in by 300mm. At 200 - 300mm, the difference between macro and infinity is more than a few cm travel into the body.
e) In a way, that article is right. you *can* physically mount the 2x TC onto the lens, there's nothing stopping you. *BUT* you can only focus at infinity, and above 200mm or so. Focussing any closer than 5m @ 300mm, or infinity @ <200mm (a guess because I don't have one in from of me) will be crunching stuff. He may have meant "it was obvious I would have to shoot using manual focus" because of the aperture, but also because if AF hunts it's going to break something.
f) It's probably ok to use a t/c if you put an extension tube in between the t/c and lens. But then you're at macro only.

 

[dr croubie]

(and the two others at 210mm or so, when the element is closest to the sensor at macro-focus)

 

[neuroanatomist]

Thanks!

I think the take-home is that it's not compatible. I mean, you can mount an EF-S 10-22mm on a 1D III, if you remove some plastic and don't use 10mm...but I wouldn't call that compatible, either...

 

[K-amps]

Thanks for the link. I agree with the one comment posted to the review - that was a pretty bad misrepresentation. As Dr. Croubie points out, the rear element of the lens is right at the back. I think he mis-typed when stating it's at 300mm - I think it's at 70mm and the rear element moves further 'in' (away from the lens mount) as you zoom to 300mm - at least, that's how most extending zooms behave (except the 24-70mm which uses a reversed design). So, it's 'compatible' at longer focal lengths, but not 'compatible' (= lens damage) at shorter focal lengths.

An apt theory.. since it will be used for longer lengths anyway, it could work.

Dr. Croubie: Thanks for the extra pics, I would not have understood it well without them.

Is lens damage really a concern? I mean there's plastic hitting glass, so unless someone is careless, I would think the risk is limited if used with the knowledge that the floating lens hunts, No AF to be used and should keep the zoom at 300mm?... I guess not worth buying a brand new 2x over the 70-300mm unless one had one lying around....