This is a quick test of my 300mm lenses.
Test camera was a stock Canon 1DMKII.
AV mode
White Balance = AWB
ISO:400, CWA metering.
Weighted tripod,"mirror lock up" and remote release were used.
Canon "IS" was turned OFF
The files are JPG's straight from the camera. NO post processing what so ever has been done. They are JPG "Large".
All focusing was centered on the red "egg" between the flowers.
Wow, I'm so glad I bought my Pentacon 300. Only serious contender for me on my M42/SD14 marathon is the Tamron 2.8/300 LD but that's a but rich for my taste - and there's little is anything to choose between the the Pentacon and 300/2.8 L in these tests - though of course f4 vs f2.8 can be a deal breaker in low light.