I too have a lense question... Relatively new to the DSLR world. I need to take sports photos of my kids. One case in particular is in football. Typically, from the stands, I'll be as far as 150-200 feet from my subject. Will it be good enough to use a 200mm lense, or would you suggest a 300mm lense?
Jmack - Hello from DMacK. Great to have you here and thanks for joining CiC.
I hope you enjoy being part of the forum and that you'll be involved for a long time to come.
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If you have a look at professionals covering field sports such as football, you'll see that they a a lot of long glass mounted up on their cameras .............And they're at the side of the pitch. So, that gives you a clue, particularly if you are even further back in the stands.
200mm will give you a fairly broad, 'context' type shot, but it is not going to isolate your kids in the frame and give you close ups of them in action. I think you'd even be struggling with 300mm.
Some of the sports shooters in here will, I'm sure, give more sound advice, but you should also do some online searching and learn what lengths some people are using.
The other thing you need to consider is the speed of the lens. If you could be in low/poor light situations, then you're going to need to be able to open up the lens to get more shutter speed (but also to effectively isolate your subjects by throwing the background out of focus via reduced depth-of-field).
Unfortunately, once you get into the world of long AND fast you get into the heady world of lots and lots of money.