What is digital noise?

[sherlock]

HI,


I am an amateur photographer and I am looking to buy a new digital slr. I have been reading a lot about digital slr's and there is one thing that I don't understand. What is digital noise? I've read that it happens at higher ISO settings but I don't quite understand. Can you help?

[jaykinghorn]

Digital noise comes from two main sources. The first being the inherent noise in the camera's sensor. This is exacerbated by heat buildup on the chip from multiple exposures or long exposures, or by having many photosites clustered onto a small chip. This is why dSLRs have less noise than point and shoots. The second source of noise you allude to is from the ISO rating. The ISO setting simply amplifies the signal through the chip, much like turning up the volume on your stereo. With the volume at 3, you can't hear the noise in your stereo, at 10 you hear the hiss through the speakers. This is amplification noise.

The best advice for avoiding camera noise. Buy a camera with a larger CCD or CMOS chip (think dSLR), and work to dial in your exposures. Underexposed images always end up being noisier than correctly exposed images.

Best of luck,

Jay Kinghorn
RGB Imaging

[sherlock]

Hi! Thanks for your explaination, it really helped. I just have one more question. I've read that noise can ruin a photograph and that people edit it out using photoshoppe or other editing software. If it is only "noise" that one hears, how is it recorded on the image?

[Mike Woods]

Originally Posted by sherlock

Hi! Thanks for your explaination, it really helped. I just have one more question. I've read that noise can ruin a photograph and that people edit it out using photoshoppe or other editing software. If it is only "noise" that one hears, how is it recorded on the image?

The short answer is that digital noise is pretty much the same as grain from a film camera. It looks like little specks in your image. You don't hear it, you see it. The higher the iso setting, the more noise (grain) you can see in the photo. Photoshop and noise specific programs such as Noise Ninja and Neat Image do a good job of making it less noticable, and in some cases almost eliminate it altogether.

[sherlock]

Thank you very much, your explaination helped a lot.