Zuiko 300/4.5 mf lens vs Nikon 300/4.5 ED IF (or Contax Zeiss 300/4?)

<p>How would you compare the two?<br /> I know Zuiko probably has more color fringe. How do they compare in sharpness and other areas?<br /> I know the Nikon 300/4.5 ED non-IF beat them all, but it is also a very rare item to find.</p>

<p>Here is a little description of my intended use for the lens:<br /> I will use the lens primarily for video. I have a Panasonic GH1 with micro4/3 to Canon EOS adapter. I have a set of primes, mainly Contax Zeiss, adapted to EOS mount. This gives me a set of primes that works for both the Canon 7D/5D and my GH1.<br>

Or would you suggest a 300mm lens made by another manufacturer? (One that is adaptable to Canon EOS) I wanted to buy the Contax Zeiss 300/4.0, but many people say it is mediocre. What do you think?</p>

<p>For video use, I have some concerns that may be not so important to still shooters.<br /> 1) I need nice smooth focus ring with a lot of rotation to pull focus with.<br /> *2) "Breathing" should be minimized - the image shouldn't zoom in and out slightly while pulling focus. I wonder if the IF design of the Nikon does that, since I know the IF design changes the focal length when focus is changed.<br /> 3) The lens and focus ring must be solid and sturdy. I used to have a Zuiko 28/2 with a focus ring that has a very slight amount of play when I switch direction during my focus pulling. It is not at all a concern to a still shooter. But that tiny amount of play is enough to shake the image and it is very noticeable on video.</p>