Noise? It beats blur. And it can be creative.
When it comes to getting the exposure right in your photos, most people are comfortable adjusting their aperture or shutter speed, but tend to shy away from cranking up the third element in the exposure triangle: ISO. Why? Well, just as adjusting aperture and shutter speed has creative implications for your photos—depth-of-field and motion blur respectively—ISO comes with its caveat: noise. The grainy effect of digital noise has long deterred people from upping the ISO in their photos, but the truth is that there's no need to be afraid of high ISOs.
Noise beats blur
Having a noisy, grainy photo is superior to having a photo that's been ruined by streaks of motion blur. Sure, motion blur might be the look that you want on occasion, in which case you go with it. But if it isn't, up the ISO and deal with the noise. And if it's a choice between grain and no photo at all, definitely go with the grain.
Cameras are improving
Until quite recently, the higher ISO values (beyond ISO 800 or so) were useless on most cameras; they really would be overwhelmingly noisy. But sheesh, camera and sensor technology has improved leaps and bounds over the past few years. If you do have sufficient light, of course it's recommended to go with the lowest ISO that you can manage. Apart from noise, it helps to maintain true colour rendition. However, if you need to increase it, go for it!
That said, it is definitely worth experimenting with your camera to determine how high really is too high when it comes to ISO. Sure, your camera might be capable of going to ISO 25,600, but if anything in excess of ISO 3,200 brings you out in noisy hives, you know your limits.
Noise can be eliminated
Okay, 'eliminated' might be over-stating things, but certainly it is possible to reduce or mitigate against the effects of noise. There's no need to send a grainy photo to the delete bin immediately.
Plenty of image editing software, for example Adobe Lightroom, has excellent noise reduction tools. A nudge here and a tweak there can make all the difference.
High ISO images tend to look uglier in colour than they do in black and white. You'll find that the noise produces unpleasant clumps of colour. Flick the switch to black and white, and taa-dah! The nasty-looking colour clumps disappear.
There's a creative side to high ISO
In some instances, a generous helping of digital noise can actually make the photo look grittier, more in-your-face, and more genuine. So why not use noise to creative effect? For example, a lot of noise conjures up images of paparazzi and film noir. You can add a sense of voyeurism to a photo or give it a feeling of unease or the industrial with a bit of noise.
The last word
Remember why ISO's important, embrace it, learn to manipulate it, and you're laughing.