Is there any professional photographer in mylot?

Well, I don't think i'm a professional although i get offers from people that want to me pay me to take their photo. So i guess i'm dencent. lol anyway, noise is the digital equivalent of film grain basically. You can get it from using High ISO or long exposures. different camera and models will be different when it comes to how much noise is seen. compact digital cameras are more prone to noise than digital SLRs cameras because of the size difference in the sensors. you can get programs to get rid of the noise. there are some free ones and then there are the ones you have to pay for... in less you have something like photoshop that has stuff like that built into the program already.

Noise has been described well by the other contributers, but to add to the discussion: what we are talking about is a poor "signal to noise ratio". As you might guess, the term came into electronics from the audio recording/amplification industry, and was then adopted by photography. Think about what happens when you turn up the volume on a sound system; at first, you just get louder sound, which makes it easier to hear. But then the sound starts to get distorted until it reaches the point where more volume ("gain") makes it harder to make out the sound you want to hear (the "signal"). In photography, the increasing the gain is achieved by increasing the sensor sensitivity (the ISO setting). Turn up the ISO above about 400 on most compact cameras and the signal to noise ratio becomes poor, the picture breaks up and you get ugly speckles. Digital SLRs can handle much higher ISO settings (and therefore can be used in poorer light conditions. There are 2 reasons for this: the sensor is larger, allowing more spa ce between the sensor sites; and each sensor site is larger, and can therefore collect more light. The main cause of signal loss is heat. Packing more pixels onto a sensor generates more heat interference between the individual sites, so more pixels does not necessarily lead to better pictures. Compacts above about 7 megapixels start to push the limits (CMOS and Foveon sensors work better), and the limit at present for standard SLRs is somewhere about 15 megapixels. Full frame DSLRs work fine even at 24Mp. If you images are already noisy, you cannot remove the noise, but by softening and selectively blurring parts of the picture can improve them greatly. Noise Ninja and similar programs do this very well, and the tools built into programs like PaintShopPro and Photoshop have become very sophisticated, too. But there are limits, so t is better to try and avoid the problem in the first place.