The sensor needs enough light to provide an output signal. If there isn't enough light/time of exposure, the output signals won't all have received enough lite so some will put out an incorrect color. The signal is amplified and these random pixels of the wrong colors will become more visible as you crop or enlarge and especially on larger prints. The higher the iso, the more "noise" is visible. Dslr sensors are larger so more light is captured per pixel and the noise problem is much less apparent...

Thank you Craig for the information. I am waiting delivery of Konica Minolta Dimage Z5. I am an artist and needed to get a camera. After reading some reports thought it was the one for my needs. But since ordering it read that it had problems with noise. I have not used a digital camera before and know nothing about photography so this is a venture into the unknown for me.

Molly..

Hi Craig, I thought the main difference is not that the dSLR sensor captures more light, but more that the larger sensor size allows the photosites more isolation/spacing from each other - and thus less crosstalk...

Noise = stray electrons (photons?) A DSLR's sensor quickly overcomes the noise level. Sensors in astrophotography are sometimes cooled to below freezing to counteract, or minimize the ambient noise. All the literature I've seen on the higher performance of DLSRs points mainly to the larger size of the CCD that enables the gathering of more light, reducing the need for a flash and reducing exposure time, making them ideal for action photos, etc. I'm sure that the distance between cells would be better for sharpness or contrast, but would do nothing special for the gathering of light. Mike..

There are a number of sources of noise. I'd be a little careful about reading too much into a review's noise comments without looking closely at sample pictures. That is unless they report the noise as being extremely obvious or overwhelmingly noisy compared to similar cameras, it may be less drastic that it sounds. Most of the digicams have compromises and if there is one that fits you, fits your needs and is a little bit noisy, maybe using a moise reduction program is better than trying to deal with a slightly less noisy camera that doesn't reproduce colors as accurately...