RE: [Leica] Trying to improve my scans

["Austin Franklin" <austin@darkroom.com>]

What I meant by brightness/contrast for B&W is that typically, in the
scanner software, that is the major control for how you adjust the scan.
There is no color balance you need to do, obviously.  Brightness/contrast
just change the curve (typically just the midtones).  Contrast changes the
slope of the curve (relationship of the values), and brightness moves the
values (adds or subtracts).

ANYTHING you do to change the data (especially in low bit data) is
technically destructive.  There are basically three types of data
'destruction' (ie, can't re-coup the info).  One is losing the relationship
between the data, and second is losing bits (or adding bits), and third
losing the baseline (really inconsequential).  The first two of these done
in the scanner software or high bit mode will be not "really" destructive,
but done in 8 bit/pixel mode are destructive, since you have no headroom to
map into.

In high bit data, the 'destruction' is mostly inconsequential, providing you
do things correctly.  The scanner hardware/software should apply all your
scanner settings to the high bit data, and give you as an output low bit
data (if you have selected it to do so).  You can make very minor tweaks to
it, but anything major will cause posterizing or reduced dynamic range.

This can get quite complex, and if you really want me to explain it, I would
be more than happy to.  I can do it on or off list if you or anyone else
like.


> How is it that Brightness and Contrast are non-destructive for
> B&W?  I thought e.g. Brightness moves the whole histogram up or
> down, and throws away bits that over- or under-flow?  Wouldn't
> this affect B&W as much as colour, or am I misinterpreting your statement?
>
> The nice thing about Vuescan is that you can get pretty good
> adjustments in the scanner software and still get high-bit data
> out. Usually all I have to do in Photoshop is crop, spot, tweak
> the colour, brightness and contrast in a Levels adjustment layer,
> sharpen and print.
>
> Paul
>
> > The first thing people need to find out is that
> > Brightness/Contrast are destructive controls, and should never be
> > used.  The second is that Adjustment Layers are Adobe's greatest
> > gift to photographers.
>
> 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.
>
> As far as brightness and contrast, that is not true for B&W.