The time has come, due to some physical limitations, to reduce the weight and size of my backpack kit. While I have a number of smaller lenses I am talking here about my 100/400 and 70/200 IS f/2.8. Want to get the new Canon 70/300 L f/4-5.6 to replace (at least) the 100/400... Hope to find a buyer for it. Will hold onto the 70/200 f/2.8 for the time being although I won't carry it in the field pack.

I have read that the Kenko Pro 300 1.4 TC works well with the 70/300L (Canon TC's don't fit). Because of the pin configuration the AF still works although some have reported that it sometime "hunts" a bit. As I use a 5D MKII for my scenic/water shots and a 7D for my birding and wildlife, the 70/300 appears to be a happy medium (480mm on 7D... 672mm w/ 1.4 TC) as it is both lighter and smaller. The IQ and IS of the lens appears to be very good and I will be happy to do away with the "pushme / pullyou" FL adjustment of the 100/400... never have gotten used to it.

Any thoughts or comments?

Also, is there any reason that I couldn't run the 70/300 - 1.4X combination through the new Reikan FoCal software to accomplish AFMA? or might it not just consider it to be a "straight" 70/300 due to the pin configuration and thus would modify the regular FoCal calibration of the lens ?

Again, thoughts or comments?

Finally, has anyone come up with an alternative to the "out of control" $180 price of the 70/300 tripod ring/collar... Canon didn't do us any favor on that one! Have heard of some "store-front" alternatives that turn out (for the most part) to be very sub-standard and vary in construction from "passable/good/metal " to (unusable/plastic).... trouble is you never know what you're going to get... even from the same "store"... I know, you pay for what you get!!! In this case I think Canon is just a wee bit "over the top".

Thanks for any input

Bill