Hi Olly,
I suspect you have to adjust the back focus. A back focus problem is indicated when you focus at tele, zoom out, and find the image is soft.
There is a special automated procedure for this, but it is deliberately made rather inaccessible. I think you can mess the camera up by doing this so be warned! Take a look at this web page from the excellent and generous Don Greening:
http://reeltimevideoworks.com/blog/pmw-ex1r-flangeback-adjust/
My personal experience: After putting the camera through the automated flange-back adjustment procedure, I still found it very difficult, even with a large star chart (16x24"), to verify correct back focus. The peaking does tend to indicate falsely that all is well; and even with a large monitor, I find it very tough to verify perfect adjustment by looking at a star chart. At some point, the radiating "rays" of a star chart blend together, and how can you tell whether they're blending at the correct point or not?
The most effective quick test I have discovered is to set the camera up inside, using ND2 and high shutter to give you a wide aperture, aim at some trees outside through a traditional window with muntins. Focus at tele on an intersection of muntins. Slowly zoom out, observing the tree branches in the distance. They should not be in focus; peaking will confirm this.
Good luck.
Bob C
