One point I want to drive home here is with my 7D. As the temperature changes I have to re-calibrate and set new settings for the two lenses. Not a problem. But something I did before the test. I find it changes from sea level to the mountains where I am currently shooting.
In the digital dark room it is hard to tell the difference between the 500 bare and the 300 with a 1.4 T.C.. This is with fill flash though. Which I think is a very important tool for avian photography. The flash also helps with the better detail. So, more testing is in order for sure. But not until I have the time or something goes wrong with the image quality.
You can go to my flickr site to view the EXIF and pics in large view.
These two lenses are my only Canon lenses. I started with Pentax and went to Canon for the excellent lenses they have. Now only interested in Canon for these two lenses. And with this test I am finally happy with my decision. The 500 ll is sharper than the older 500 IS ( which I had ). Which was a first class lens and the best in my opinion before the new 500 ll was introduced. The 300 ll is also sharper than the older 300 IS lens ( which I had ). Not to mention the IS is amazing.
The only problem I have now with Canon is. It needs to give the birders a good 1D quality crop sensor camera to really make these lenses shine. For my needs the new FF cameras are just a joke. But the main thing is. Canon is not showcasing these two lenses with the FF low pixel density sensors. If they come out with a 1.5 or 1.6 crop sensor camera with excellent AF. They will rule the tele-photo lens market. IMO no other company will be able to touch them for years if this happens.
Go birding, Gary