Re: [ARSCLIST] Shopping for AD/DA

[phillip holmes <insuranceman@xxxxxxxxxx>]

I ran into that problem when I was designing my web page.  The pictures 
were resized, stretched a little, brightened, and the quality was 
reduced so it wouldn't take too long to download.  The end result was 
awful.  After just a couple steps, the digital artifacts started showing 
up.  I just figured it way my free Photoshop program (you get what you 
pay for).
Phillip

Don Cox wrote:
> On 11/07/07, phillip holmes wrote:
>
>   
> > I know you weren't. That was merely an "amen" for Bob. Most decent
> > ADCs can give good results, if they are used correctly. That's why I
> > don't like those "restorations". They "put lipstick on the pig" and
> > the result is unacceptable for me and the pig.
> >
> > There was a great article about Pro-tools a while back. It explained
> > how all that manipulation in the digital domain gives such a bad
> > sounding product because every manipulation of the original signal
> > looses bit depth (or something like that---I'm an idiot about
> > digital). Phillip
> >     
>
> If you have access to Photoshop, you can see a visual equivalent.
>
> Load in a color photo, ideally one that is too dark. Go to
> Image->Adjust->Levels (or "Adjust Lighting->Levels" in PH Elements).
>
> You will see a histogram showing 256 levels of brightness.
>
> Adjust the sliders, which is the equivalent of adjust levels in audio,
> so that the photo looks better.
>
> See how the histogram breaks up - there are no longer 256 levels. The
> gradation is now jumpy.
>
>
> This is because, to change levels, the computer must map some pairs of
> levels onto single levels. The more steps you have to start with, the
> less trouble this causes. 
>
> Regards
>