On 8/23/03 8:56 PM, "Jeff Keller" <jrk_om@xxxxxxxxxxx> wrote:
> The Min*lta scan utility I use provides "the color depth can be selected
> from 8 bit, 16 bit, or 16 bit linear". I use the 16 bit option. I saw a
> number of newsgroup posts about compressing the image file but didn't
> try to follow them.
>
> I've read claims that manipulating an 8 bit image can result in problems
> but that 8 bit is just as good for printing.
>
> I've got a lot I need to learn about it.
Most scanners will give you the ability to scan the image at greater than 8
bits per channel (24-bit RGB). In terms of what you're viewing on the
screen, you're only going to see 24-bit colour (8 bits per channel). You
don't need to be able to see more than that because that's the extent of the
visual spectrum. This is also why 8 bits per channel is "just as good" for
printing.
However, when you are editing an image, it helps to have that extra colour
data. The reason is that when you adjust the levels of an image, you end up
throwing away data. Having extra colour data gives you the headroom you need
to make these kinds of adjustments and still get smooth colour transitions
after the fact.
If you don't adjust your levels with more than 8 bits per channel, then you
can start to see banding appear in colour transitions and also posterization
effects. How noticeable these effects are is really going to depend on how
much of an adjustment you make to the levels (the more extreme the
adjustment, the more noticeable the effect will be).
--
Andrew "Frugal" Dacey
frugal@xxxxxxxxxxxxxxx
http://www.tildefrugal.net/
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