New MKII versus old 300mm f2.8 IS L A/F

Seeing a few of these are begining to appear in the hands of people does anyone have any experience on real world A/F performance of the newer MKII compared to the older lens for motorsport?

My 300 is great on its own and not much of a difference with the 1.4 MKII tc but takes a hit with the MKII x2 when shooting bikes.

I am aware that the best performance of the new whites is when coupled with the new MKIII tc's but if the A/F is up a notch on the previous version then i could still get away with using my MKII tc's for now till i have the funds to replace them with the MKIII's.

Have been offerd £3000 part ex on my old mint 4 year old lens against the MKII so am tempted to take the plunge now while there is quite a good return for minimal loss on my old 300 rather than wait till next year to see if the initial price comes down more on the new MKII when by which time the seconhand value may drop way back again.

If you need to use 2xTC why not just get 500mm f4 IS ver I? 300mm f2.8 IS II is expensive IMHO compared to 300mm f2.8 IS I.

bobbyz wrote in post #13229166
If you need to use 2xTC why not just get 500mm f4 IS ver I? 300mm f2.8 IS II is expensive IMHO compared to 300mm f2.8 IS I.

Im trackside so sometimes a 500 f4 is to long and i can still get away with panning with the 300 f2.8 even with the 1.4x and 2x so the 300 is a much more versatile tool for my needs and shooting style.

My present 300 is the perfect all round lens for my needs but would benefit with a slightly quicker A/F responce when used with TC's hence my post.

Would be great to have a 300 and 500 but best compromise for me is the above.

Which body are you using?

Mainly use the 1D MKIV but have a 7D as backup.

Hum. I never liked 2xTC AF wise on my old 1dmk2. Check naturescapes.net to see how much better the AF is on the ver II. I can't expect it to be that good when using 2xTC that you need to spend twice the money.