i there,i'll just start off by saying that i have absoultly no knowledge on this subject.i've just bought a samsung gx10 with an 18-55 lens..i havent got it yet ,it's in the post..i hope..my question is this..i intend to use it for taking pictures of my kids horse riding in an indoor arena where the light is not great,also they will be jumping over jumps..so i want to get action shots..also for general holiday photo's..landscape's etc..i am thinking of a 50-200mm lens..will that be too slow for the low light,or will i have to spend big money on a faster lens..i dont want to buy the wrong one and have to get another one..or mabey i'll need 2 anyway??,as you can see i am a complete beginner..thanks