75-300 DO vs Regular USM IS

[MadMesh]

my 75-300 USM IS lens, falls off after 200mm .. Pictures are super soft. Its pretty muched used as a 75-200 for me...

Does the DO version of this lens have sharp optics from start to finish? Or is it similar to the 75-300 just smaller?

Trying to Justify the cost, otherwide id just go out and pickup a 70-200 f/4. And eventually one day get a 100-400.

[Skip Souza]

IMNHO if reach and sharpness is more important than physical size ;-) just go straight to the 100-400 L IS. It is only $250 more than the 70-300 DO IS and you will have it all :-)

[Skip Souza]

P.S. I had a Tamron 28-300 that tended to be soft at the ends. I discovered that by tightening the aperture I could get much sharper images clear out to 300mm. F/8 was good, f/11 was better.
My wife's 75-300 IS USM was much the same.