I can't answer your P&S question. I've got a P&S and I've used it for family snaps and such, but it has far to many limitations for my taste especially when shooting sports. It' seems best suited to stills-still life, in-animate objects... I've never used one to shoot sports in any serious fashion.
The crop factor or magnification factor or what ever else you may have heard it called with respect to 35mm VS digital sensor 'size' has nothing to do with either magnification or focal length per se. It effects the field of view-hence the crappy term 'crop factor'. There is a precise calculation but for general use it's about 1.5 in the aps-c sensor wrt 35mm situation.
If you multiply the 35mm lens focal length by the 1.5 factor you get a new, longer focal length that is meaningless (because the lens doesn't magically grow) except as it relates to field of view. A 50mm lens on a 35mm film camera will generate a 75mm field of view on the aps-c sized digital camera--i.e. smaller. So if you fill the frame with a standing man on the film camera some will get cut off on the digital if you stand in the same place to take the shot. It appears to give an greater magnification-but it doesn't.
And unless you really need the math and all the hang-ups entailed it doesn't really matter. Ultimately you will need to adjust to the digital environment and that means using shorter focal lengths than were typical in film cameras to get similar fields of view. That's the total extent of the 'adjustment' and it is readily learned with a little practice.
Rule of thumb: to get a
field of view of an 'N' focal length film lens use an 'N/crop factor' length lens on a digital camera.
Originally posted by reoterq I would have liked the K10, but budget limitations and the fact that the kit lens wasn't going to do the trick for indoor made the k100 the obvious choice for a beginner.
I really would like someone to comment on this, and maybe I didn't state it so well, so I'll try again: What is the "rule of thumb" when correlating SLR zoom to DSLR zoom?
Along those same lines, I've been used to a point and shoot with 3X optical zoom. What is comparable (how many millimeters) to that in DSLR?