On Sun, 7 Mar 2004 16:16:27 +1000, Tanya Mayer Photography wrote: > >Oh, and one more thing, that I have been meaning to ask for ages, and I fear >that I may be opening a can of worms here <vbg> but can someone explain to >me about "bits" ie what is the difference between 8 bit and 16 bit files? > >*tan runs for cover as all the tech heads begin to furiously type trying to >beat each other to the best explanation* lol!
Tanya, Everything digital is made up of bits. It's the ones and zeros that everyone talks about. Everytime you add a bit you double the capacity. 8 bits gives you a range of 256 possibilities. 9 bits gives you 512, 16 bits gives you 65536. In 8 bit colour you get 8 bits of information or 256 levels for each red, blue and green - also called 24 bit colour (3 times 8 bits for each colour) a total of over 16 million colours. In 16 bit colour you get 16 bits of information or 65536 levels for each red, blue and green - also called 48 bit colour, a total of 281474977000000 colours. In the black and white world you only get 256 shades from an 8 bit image, 65536 from a 16 bit image. Most digital cameras and scanners actually give you 12 bit colour which is either converted down or up to 8 or 16. 12 bits gives you a range of 4096 shades. Digital cameras manipulate the white balance by using the extra bits to internally adjust colour levels to give a good 8 bit image. You may be wondering why you need this many colours. 24 bit colour gives you imperceptible tonal graduations, but once you start playing with levels and contrast and so on in photoshop you can easily cut this to half, quarter or eighth and then you start to see the graduation from one colour to the next. Using 48 bit colour, you can take an image and manipulate it to death and still get excellent tonal graduations. I always use 48 bit colour space for editing images and convert it to 8 for the final image. Hope this helps Leon http://www.bluering.org.au http://www.bluering.org.au/leon
