spots on photographs

[kkasscarm]

what causes spots on photographs?

 

[NetSquirrel]

Following on from allen, with digital cameras the blotchiness effect is known as "noise" and is caused (as far as I know) by the size and number of the tiny light-sensitive components that make up the camera's sensor plate.  A camera only has a limited amount of light-gathering capability, therefore in low-light conditions it is often necessary to "boost" the weak signal received by the sensor (done by turning up the ISO) so as to avoid a photo that comes out too dark.  This means, however, that any tiny difference in lightness between neighbouring pixels on the original image will be amplified to produce the final, not-too-dark image.  The size of the sensor also makes a difference.  With, say, a 5 megapixel sensor of area 60mm�, there is a certain amount of light-gathering potential per light-sensor there.  If you then take the same photo but replace the sensor with another 5 megapixel one but with area 300mm�, that is a lot more light falling on the sensor, so less amplification is required, so you get less noise.  If your photographs are all coming out covered in speckles (most of mine do) then you can reduce this effect to some extent with special noise-removal software such as NeatImage or Noise Ninja.  Here is a photo I took of a fish (1:1 crop straight from my camera) in low light http://www.dpchallenge.com/image.php?IMAGE_ID=119454 .  Here is the same photo with some selective noise-removal and a couple of other enhancements http://www.dpchallenge.com/image.php?IMAGE_ID=119454 .  I know I haven't provided a very good explanation, but the point is the spots needn't ruin your photos.