Sharing a Moment

A moment shared -- 1D IIn & EF 85mm f1.2L @ f1.2, ISO 400. Click to see larger

One of the biggest advantage of having a very fast lens is that you can shoot in dim lights with relatively low ISO and fast speed.  Even better if the lens is usable at it's widest aperture.  The Canon EF 85mm f1.2L is such a lens.  Absolutely my favourite next to the 200mm f1.8L.  It's much more portable, and a full stop faster than the 200mm f1.8.  The 85L is stunningly sharp at f1.2, if focus is nailed, which is quite often with the 5D/1DII.  Less so with other cameras I have tried.  To be sure, there are drawbacks.  Mainly the high price, slow(ish) focus, prone to purple fringing (so is the 50L), and a bit heavy (although after using the 200mm f1.8L, the 85L is featherweight).

The 85L is a lens I always take with me when shooting in dim lights.  It does not have the focus shift problem of the 50mm f1.2L, and I can always count on its image quality, even shooting at f1.2.  If you can justify it, you will love it, and may never shoot another 85mm lens again.