Most point-and-shoot digital cameras have an ISO range from 200 to 800. A few of the nicer models extend from 200 to 1600, and an elite few at the highest-end extend from 200 to 3200 (Casio's EX-H20G comes to mind). We'll focus on the majority here in order to drive home a point. Chances are, the average point-and-shoot that you pick up will top out at ISO 800. If you force this camera to shoot at ISO 800, you will still have trouble shooting handheld images in low-light scenarios. Why? The inverse relationship between ISO and shutter speed.

You see, when shooting in low-light, there are five main things you can rely on to get a decent, visible, usable shot:

1. A flash. This works almost every single time, but it usually blows out your shot, makes everything in the center a blinding white, and generally makes pictures look "fake." Consider the use of a flash your last resort, but on a point-and-shoot, it's likely to be a must.
2. More light. If you have an indoor family portrait that you're struggling with, try taking things outdoors. The sunlight vastly improves shots, and you should always seek outdoor light first and foremost before turning to a flash, a heightened ISO setting or a slower shutter. Natural light is king.
3. Increased ISO setting. In general, the higher the ISO value, the faster your shutter speed can be while still grabbing a usable shot. Conversely, your shutter will need to be slowed as your ISO value is dropped in order to prevent an overly dark photograph. Unfortunately, specks of "noise" and grain are introduced with each heightened ISO value, so it's never as simple as just "maxing out the ISO," at least not if you care about image quality.
4. Slowed shutter speed. If you slow your shutter to 1/8 of a second (as an example), you'll probably be very impressed with how much light can be captured. Unfortunately, anything slower than 1/60 of a second is nearly impossible for a human to shoot handheld without introducing blur, and that's for still life. If your subject is moving, you'll need to shoot at around 1/160 of a second or faster to ensure that nothing is blurred. Of course, if you use a tripod and / or a remote shutter trigger, handling these slowed shutter speeds becomes much more possible, though the setup process is far slower than simply pulling a camera from your pocket, pointing, and shooting. Sadly, most P&S models will not allow you to manually slow the shutter (or adjust the f/stop, for that matter).
5. Lower ("open") your aperture. If you have an interchangeable lens camera or DSLR, and you can adjust the f/stop of your lens, tweaking that number lower will allow more light to flood in but will simultaneously give you a shorter depth of field. This means more of the background will blur (introducing an effect known as "bokeh"), but it's a great way to grab more light. Most P&S cameras will not give you this option.

For example's sake, let's say that you're no fan of your camera's inbuilt flash. Let's also say you don't have a tripod handy. Finally, let's say that you're stuck indoors in a low-light situation with no way to increase the amount of ambient light. This scenario is more common than you may expect. This is the exact scenario that most encounter when going out for a family dinner. This also describes most wedding receptions. Sadly, this also describes most hotel rooms that you'll want to capture on vacation.

Now, with your camera set at ISO 200, you'll notice one or two things. One, there's essentially no grain or noise to be found. But unless your shutter speed is extremely slow (approximately 1/60 of a second or slower), your image will be almost completely dark. That's no good for anyone. For example's sake, let's set the shutter to 1/160 -- assuming you have a camera that allows you to adjust this setting. In a dark room, with the shutter at 1/160 of a second or so (fast enough to shoot handheld without blur), and ISO at 200, with the flash off, you'll basically get a black shot. Go ahead and try it. Your results will almost definitely be too dark. Here's where you realize what kind of magic lies in the ISO value. Keeping all other settings the same, bump that ISO value to 800, or 1600 / 3200 if your camera supports it. Now take the same shot. You'll notice a much, much brighter imagine, albeit one with some level of grain or noise. In some cases, even "maxing out" the ISO isn't enough -- you'll simply be forced to slow the shutter and use a tripod or let the flash fire.

But since we're focusing this article on ISO, let's talk a bit more about that noise and grain. Basically, you'll be able to take clearer, more visible shots in low light as you bump the ISO value higher (assuming your shutter speed remains the same!), but the compromise is that you allow more noise and grain into your shots. It's a tradeoff, so to speak. The inverse is true as well. As you back the ISO value down closer to 100 or 200 (whatever the minimum is for your specific camera), you'll see darker images, albeit ones that are very sharp. The goal is to strike a balance. Find an ISO setting that introduces a bearable amount of noise, yet still gives your camera the ability to take more visible shots in dim situations.

If you're able, it's always preferable to slow the shutter speed in order to take the pressure off of your ISO value. But unless you have a tripod and / or subjects that aren't moving, that's not always an option. This very reason is why ISO values on cameras are so important, particularly high ranges. The higher the ISO range on your camera, the better off you are after sunset and indoors. If your DSLR, for example, can reach ISO 6400, you can manage to grab more visible shots than a similar DSLR with an ISO ceiling of just 3200, all other settings being equal. Taking that to an extreme, Nikon's D3s has a native (non-boosted) ISO range of 200 to 12,800. Needless to say, having an ISO value of 12,800 at your disposal means that you can take very useable images in near-darkness, but of course you'll have noticeable grain to deal with. But when it really comes down to it, you'd probably rather have a noisy shot of your anniversary dinner than a shot distorted by blur or simply too dark to make out what's going on.

In case I haven't convinced you, buying a camera with a wide ISO range is very important. You'll probably end up taking more low light pictures than you'd expect, and it's always nice to have a high ISO range to resort to if you simply must get the shot. In general, the higher the price on a camera (be it a point-and-shoot, an interchangeable lens / Micro Four Thirds camera or a DSLR), the higher than ISO range will be.

My overly simple advice here is to buy the camera with the highest ISO range that you can afford; you can never have too high of an ISO value at your disposal. Nikon's D3s is the current ISO king, but retails for over $5000. Panasonic's Lumix DMC-GH2 Micro Four Thirds camera just recently started to ship in the U.S., and it has set a new bar for ISO range on a Micro Four Thirds camera. It can reach as high as 12,800 and retails for just $900. Casio's Exilim EX-H20G has a surprisingly great ISO 3200 setting, and it's amongst the best out there for low-light shooting in the point-and-shoot arena at $350.

Let's recap:

• The higher the ISO, the greater your camera's ability to shoot in low light (with the shutter speed remaining equal)
• The higher the ISO, the more noise and grain are introduced into your images
• The lower the ISO, the more you'll need to rely on external light sources, a flash or a slowed shutter
• "Maxing out" your ISO can help you capture a shot you otherwise wouldn't get, but if it results in too much grain when you preview it, you should consider using a flash, slowing the shutter speed, using a lower f/stop (which decreases the depth of field and blurs more of the background) or seeking more light via lamps or by heading outdoors

Stay tuned for more tips on understanding shutter speed, metering, f/stop, white balance and more!

Dana Murph is a creative photographer based in Raleigh, North Carolina. You can view more of her work at Dana Jo Photos and contact her via Twitter at @danajophotos.