Digital cameras excel in low light, especially DSLRs that enable you to increase your ISO to 400 and above without excessive compromise in image quality... or, at least, it's often worth the tradeoff to get the shot.
But there's more you can do beyond simply jacking up the ISO. An effective technique to capturing good images in dim conditions is to actually get more light to the image sensor. An easy way to do this is acquire a "fast" lens, such as a 50mm prime lens that's rated at a maximum aperture of f-1.7 or f-1.8. An f-1.8 lens, when set to its maximum aperture, transfers much more light to the image sensor than a zoom lens with a maximum aperture of f-4, for example. Take a look at this sequence of f-stops on a standard 50mm lens:
1.8 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22
Each of these f-stop settings correspond to one full ISO setting:
100 - 200 - 400 - 800 - 1600 - 3200
So let's say that your f-4 zoom lens requires you to increase your ISO setting to 800 to get a reasonable handheld shot (let's say 1/30th or a second at f-4) in dim lighting. In that same lighting condition, your 50mm prime lens set to f-1.8 would allow you to shoot the same shot at ISO 200 (1/30th of a second at f-1.8) instead of ISO 800. By letting more light through to the image sensor (f-1.8 vrs f-4), you are able to lower the ISO setting using the same shutter speed.
Speaking of shutter speeds, they fall into this equation also. Here's their sequence:
1/15th - 1/30th - 1/60th - 1/125th - 1/250th - 1/500th
So with a f-1.8 lens, you may decide to keep the ISO at 800 and increase the shutter speed to 1/125th of a second instead. This would make it easier to freeze action. These are the sort of options you enjoy with a "fast" lens. Here are the numbers again, all stacked on top of each other:
What are examples of these magical "prime" lenses. You can get a Nikon 50mm f-1.8 lens brand new for $105, and cheaper used. Same goes for Canon mount. A Canon 50mm f-1.8 lens can be had brand new for $80, and even less used.
Listen to the Podcast
Now that I have your curiosity piqued, it's time to listen to today's audio show titled, "Low Light Photography." You can download the podcast here (34 minutes).