Quite a few PMW-300 users have been having issues with Chromatic Aberration (CA) typically pink and blue halos around areas of high contrast. CA is caused by the fact that different wavelengths of light are bent and focussed at different points by the lenses. So blue light will be out of focus when red is in focus and vice versa. There are two ways to combat this. The first is the use of combinations of special (and often very expensive) glass that compensate for this, the other is electronic correction performed in the camera. One issue with the optical approach is that the sharper you make the lens the worse the problem becomes, as if you bring red into very precise focus, the slight defocus of the blue becomes more noticeable. So as we raise the resolution of the cameras we shoot with and this need ever sharper and higher resolution lenses the problem becomes harder to deal with purely optically. As a result modern video cameras rely more and more on electronic CA reduction, sometimes called ALAC (automatic lens aberration correction).
Sony’s EX cameras include ALAC and it does a really good job of masking the CA. The PMW-200 and PMW-300, even though they both use the same lens as the EX’s show a lot more CA. Sony have now addressed this and released firmware updates for both the PMW-200 and PMW-300. It appears that with older firmware versions the ALAC only compensated for horizontal aberrations. The new firmware improves the horizontal correction and adds vertical correction. The difference this update makes is in most cases quite dramatic, almost totally eliminating the CA.
You can download the updates from here: http://support.sonybiz.ca/esupport/Navigation.do?filetype=Firmware