In ~15 days time, I am buying a Pentax Kr and a selection of lenses. I'm relatively new to slr photography, though I have owned a Canon G10 for a while now, and was also recently the proud owner of a Panasonic GF1 for three weeks before it was stolen. (Woo travel insurance).

I'm trying to plan my initial lens selection, and I have come across a statement on the internet that confuses me, and may cause me to re-evaluate a few things once it is explained (assuming it is even true, but it seems to have credibility.)

I found it while researching what focal length I want in a fast prime to be used for indoor volleyball shots when I get back to Sydney next year. On the steve's Digital Camera forum, I found this:

50mm = 15 feet
85mm = 25 feet
100mm = 30 feet
135mm = not familiar with
200mm = 75 feet / 25 yards
300mm = 40 yards
400mm = 50-60 yards

Min distance depends on the camera - full frame obviously you can get more of your subject in the frame. And contrary to myth, using a 1.6x sensor camera doesn't really allow you to shoot from further away. So shooting these short primes on a 1.6 can be a bit problematic.
From my own rudimentary testing (I don't have a volleyball court nearby, but I played for 15 years so I just estimated a distance from a random person, and tried a few focal lengths until I found one that made the person more or less fill the frame) 50mm is what I want.

But what is the deal with that line:
using a 1.6x sensor camera doesn't really allow you to shoot from further away.

How doesn't it? Someone else in the thread mentions using 85mm for volleyball shots, but don't indicate whether they use ff or crop, or even how close to the sideline they are able to get.

I almost wish I hadn't read the thread - I was nicely confident that the 50mm is what I wanted, but now I am worried that I will buy something I never use.