Upgrade Path Advice...

[pjn0629]

I shoot a lot of cyclocross with my 6D (gross understatement actually). I've gotten great results with it. Possibly because cross is so up-close, and as you said the speeds are pretty low so the 6D has no trouble keeping up with the action. Possibly though, it's just better than all the naysayers want to admit. Typically I use a 24-70 2.8 (Cannon mkii now, Tamron for about 18 months). In addition a friend shoots with one as well, usually with a 70-200 2.8, she gets fantastic in-the-action photos. I do see limitations, particularly frame rate, and the 7Dii looks very appealing, especially if it gives better IQ than the previous generation of APS-C sensors. I own a 60D and SL1. Nice cameras, but I see the difference between them and my 6D IQ wise. If I could've afforded a 5diii I would've bought it, but I'm happy with the 6D.

Great shots there, See I knew CX wasn't too fast for the 6D, but given most of my friends and teammates are in the lower categories, lots of chances to get them eating it in the mud, which will definitely be better with 10FPS... I'm really curious to see how the 7DII's IQ is. I'm beginning to think that I might want to wait for a 6DII or a screaming deal on a 5DIII before I make the jump to Full frame, since it appears that modern APS-C is leaps and bounds beyond what I have now

 

[Nethawk]

There is a workaround, look on TDP site:

The Canon 70-300 L is officially NOT compatible with Canon extenders. This is the only Canon L zoom lens with a widest focal length of 70mm or longer that is not compatible with Canon extenders (as of review time). I've tried mounting Canon extenders to the 70-300 L - and they do not fit. The rear 70-300 L lens element physically hits the front element of the extender.

Then, in a major firmware update announcement for the Canon EOS 1D X, Canon included the 70-300 L and Canon EF 1.4x III Extender combo on a compatibility list.

Intrigued, I did more experimenting. What I learned is that the 70-300 L's rear element retracts into the lens far enough that, at about 250mm, there is enough clearance for Canon extenders to mount.

The available with-1.4x focal length range is about 350-420mm and 500-600mm with the 2x installed. Zooming out wider than the 250mm-or-so zoom ring mark results in a physical bump inside the lens. I'm guessing that it is the rubber around the edge of the extender element contacts the rear 70-300 L lens element or its barrel. I do not recommend mounting this combination due to potential damage the to lens.

I of course felt the need to try out these unsupported combinations. My solution to the damage risk issue was to Gaffer Tape the lens zoom ring to lock it at the 300mm mark while using extenders.

Mounting a 1.4x or 2x extender behind any lens reduces its aperture range by 1 or 2 stops respectively. At review time, only Canon 1-Series bodies can autofocus when using the very-dark f/8 max aperture the 70-300 L lens and 1.4x extender combination yields. Tested 1D X and 1Ds III bodies autofocused this combination.

No bodies can AF with the even-darker f/11 max aperture the 70-300 L and 2x combo yields. While it tries, the tested 1Ds III body cannot lock focus with this combination.

The interesting part of this story starts with the fact that the Canon Extenders do not report their presence when mounted behind the 70-300 L. The reported max aperture incorrectly remains f/5.6.

And what is much more interesting is that the 70-300 L and 1.4x combination's f/8 max aperture combination autofocuses even when mounted to the 60D (and presumably on most/all other Canon EOS bodies). Autofocus speed with the 1.4x extender is very, very slow on all tested bodies, but AF does work - even on the 60D.

Since I'm sure you are wondering what the image quality from these combinations looks like, here is a look at the Canon EF 70-300 L with EF 1.4x III Extender ISO 12233 image quality. Image softening from the 1.4x is very noticeable at f/8 in mid and outer regions of the image circle, though the center of the frame remains reasonably sharp. CA becomes pronounced with increasing amounts visible toward the outer image circle. Stopping down to f/11 results in modestly better image quality.

Thank you. Kind of risky, I think I will try the Kenko first.