Archived posting to the Leica Users Group, 2001/03/12

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: RE: [Leica] Trying to improve my scans
From: "Austin Franklin" <austin@darkroom.com>
Date: Mon, 12 Mar 2001 17:06:23 -0500

> > You should do most, if not all, of your adjustments in your scanner
> > software, unless you scan in either raw mode or high-bit mode.  If you
> > don't, you will get posterizing.
>
> Agreed, that you should get as close as possible with the scanner
> controls. I don't think it is categorical that you will get
> posterizing if
> you don't.

You absolutely have to get posterizing if you apply any changes to 8 bit
data.  You may not see the posterizing, and you may just compress your
dynamic range, but any time you do not have headroom (ie, more bits than you
need) you lose data when re-mapping it.

> > As far as brightness and contrast, that is not true for B&W.
>
> The advantage of working with levels is that you've got some visual
> clues in the histogram, which you don't with the
> contrast/brightness adjustment. I can screw up an image with c/b if
> I try.

I don't understand what you mean.  Histogram is histogram.  It gives you a
list of all the values of the data from 0-255, and how many pixels have each
of these values.  Using brightness/contrast will, of course, change the
histogram.

Be aware if you are using PS, I believe you need to be viewing it a
particular way for the PS histogram to be correct...whether it's fit on
screen, or actual pixels, I don't remember...I use the histogram in my
scanner software, not the one in PS.