q. what do those numbers in the focal length mean?
a. those numbers give the focussing capability of the lens of the cam. a 4.8mm focal length means that the lens can capture an image at a minimum distance of 4.8mm. if the object is any more nearer to the lens (say abt 4mm) then the cam won't be able to properly capture the image, rather i won't be properly visible neither can it be recognised.
hence in the world of focal length, the minimum number the better! so a phone wid 3.8mm focal length can capture the image of an object which is at a distace of 3.8mm. but such close distances appear only when taking macro (close up) shots.
but one thing to be noted is that the lesser the focal length doesn't always mean the best cam. the image quality depends on a number of factors. for. eg, the w700i cam has a focal length of 4.3mm. meaning, that if an object is at a distance of 4.3mm from the lens then a w700i can capture the image while the k750i cam cannot! but everyone knows that w700i doesn't haf AF, hence the k750 is a better phone wid macro mode and AF. also if we look at k550i, its focal length is lesser than that of k750i so its cam shud be better.but since the image quality depends on various factors k750i beats it. so lesser number is better.... but only for macro shots.
@chetan55
dun get confused wid all this discussion. this was jus an explanation for the focal length. go ahead and buy the k750i. its cam is slightly better than k550i while its the cheapest phone who's cam can beat the costliest 2mp phone's cam!