While taking pictures outside in the day is rarely a problem in terms of available light, it's not uncommon to find yourself shooting indoors or late in the day when light is in short supply.
Your first options are to lower your shutter speed or use a flash, but if you can't do either then you may need to raise your ISO setting.
But there is a price to be paid for this, such as sacrificing fine detail, or an increase in intrusive ‘noise'.
Noise is talked about a lot in digital photography and is usually considered undesirable. Images shot at really high sensitivities can appear soft, lacking fine detail and with intrusive noise and derogatory colour. Or at least they used to.
Advances in sensor design and image processors are now producing DSLRs that can shoot in low light at high ISOs and still produce a great image with less noise.
Nikon has been at the forefront of this trend in recent years, especially with its mid- to high-level DSLRs, but other brands have since caught up or aren't far behind.
When looking though our camera reviews to choose a new camera, be sure to read what our testers had to say about the ISO capabilities and noise of each model.