Ok so this is probably just a n00b question, but I'm a little discouraged.
This weekend I shot in an indoor paintball facility where the lighting was much less than optimal, which required me to use a very high ISO (6400 to be exact). Now I understand that higher ISO's create more digital noise in the pictures and what not, but what I'm bothered about is that several of the pictures are useless because of that noise.
So, I'm curious, would a better lens help with that, or is it completely a limitation of using a high ISO?:o
Well, if you had a faster lens you wouldn't have to use as high an ISO. Taking a shortcut by getting a faster lens that has a narrower field of view, however, does not necessarily work, because you lose light when you crop. It doesn't matter how much exposure is in the frame if you throw much of it away, cropping. It's the actual size of the aperture (focal length divided by f-stop) that determines how much light you capture from your subject from a certain distance, not the f-stop.
You might want to experiment with shutter speed. You might not need it as fast as you think you do, and if you want to convey motion then you don't want to freeze the fastest moving thing in the frame.
The way you view or process your images has a huge effect on perceived noise. It makes no sense whatsoever to sharpen an image at the pixel level, and then downsample it. Sharpening should always be done as a last step. Sharpening images before downsizing only adds noise and artifacts. Also, many programs that people to use to view images on their monitors greatly increase noise by using the "Nearest Neighbor" downsizing method (or a similar hybrid), which greatly increases image noise. You want to use the option for smoother results, or a program that offers that option. It is very easy to see what I am talking about in FastStone Image Viewer; at the menu at the bottom of thescreen, it has a toggle called "Smooth". If you check it, the image is more properly downsampled; if you uncheck it, it is potentially aliased, and very noisy. Same concern applies to the method you use to resize an image in an editor; most have options, with Laczos being the best usually, and nearest neighbor (sometimes called other things) being a total disaster for images that are noisy or sharp to begin with.