combining multiple scans of same image for greater bit depth

combining multiple scans of same image for greater bit depth

Post by Mikare » Sat, 17 Jan 1998 04:00:00


This is an idea I've been toying with based on the old photo lab technique of
contrast masking, and I've been wondering if I'm just whistling dixie, so
comment away:
How could one assemble, in perfect registration, two or more scans from the
same transparency, each tailored to optimize a small portion along the H&D
curve? Say one makes scan #1 to keep highlights from blowing out at the
expense of shadow detail and combine it with scan #2 that gets deep into the
shadows, forsaking highlight detail. It seems that if you could combine these
accurately in PS, you could get the bit depth performance of a PMT drum scan
from your garden variety flatbed. Any ideas how I could try this within PS4?
Thanx.

 
 
 

combining multiple scans of same image for greater bit depth

Post by David Kyt » Sat, 17 Jan 1998 04:00:00


Put your pics on separate layers. If you double click on the top layer in the
layers pallet a box will come up that has settings for how that layer combines
with the underlying layer, at the very bottom are some sliders that will allow
you to control the opacity of the highlights only  or shadows only  of the
layer, pull these to drop out the light or dark areas. By option (alt) clicking
on one of the divided triangle sliders you can control the feathering of the
transition.

One of those things that PS can do that not many people know about.

Good Luck


> This is an idea I've been toying with based on the old photo lab technique of
> contrast masking, and I've been wondering if I'm just whistling dixie, so
> comment away:
> How could one assemble, in perfect registration, two or more scans from the
> same transparency, each tailored to optimize a small portion along the H&D
> curve? Say one makes scan #1 to keep highlights from blowing out at the
> expense of shadow detail and combine it with scan #2 that gets deep into the
> shadows, forsaking highlight detail. It seems that if you could combine these
> accurately in PS, you could get the bit depth performance of a PMT drum scan
> from your garden variety flatbed. Any ideas how I could try this within PS4?
> Thanx.

--
David F. Kyte
http://home.att.net/~davekyte

 
 
 

combining multiple scans of same image for greater bit depth

Post by Mike Engle » Sat, 17 Jan 1998 04:00:00



> This is an idea I've been toying with based on the old photo lab technique of
> contrast masking, and I've been wondering if I'm just whistling dixie, This is something discussed in a book called "The Essentials Of Digital

Photography". It is very expensive at 56UKP. It is very informative
about all aspects of digital imaging.

Mike Engles

so

Quote:> comment away:
> How could one assemble, in perfect registration, two or more scans from the
> same transparency, each tailored to optimize a small portion along the H&D
> curve? Say one makes scan #1 to keep highlights from blowing out at the
> expense of shadow detail and combine it with scan #2 that gets deep into the
> shadows, forsaking highlight detail. It seems that if you could combine these
> accurately in PS, you could get the bit depth performance of a PMT drum scan
> from your garden variety flatbed. Any ideas how I could try this within PS4?
> Thanx.

 
 
 

combining multiple scans of same image for greater bit depth

Post by Jegs1 » Sun, 18 Jan 1998 04:00:00


As far as that goes, you really can't.
Scanners have a predetermined range of how much shadow detail that they can
see. You really can't bring out anything that the scanner doesn't see.
Using a high percentage of unsharp masking, with a small pixel spread will
really sharpen and bring out detail.

 
 
 

combining multiple scans of same image for greater bit depth

Post by Zeitbau » Sun, 18 Jan 1998 04:00:00


this is a topic that came up in publisher mag in 96..  athough the author of
the helptopic wanted to take photo multiple exposures of subjet.
cool thing with ps is that you can combine two workings of the same image as a
composit... get a kind of hologram surface at the intersection of the two
layers... can get very subtil effects. two contrasts or two color balances...

moik

 
 
 

combining multiple scans of same image for greater bit depth

Post by terrap » Sun, 25 Jan 1998 04:00:00


On Fri, 16 Jan 1998 08:07:43 -0500, David Kyte


>Put your pics on separate layers. If you double click on the top layer in the
>layers pallet a box will come up that has settings for how that layer combines
>with the underlying layer, at the very bottom are some sliders that will allow
>you to control the opacity of the highlights only  or shadows only  of the
>layer, pull these to drop out the light or dark areas. By option (alt) clicking
>on one of the divided triangle sliders you can control the feathering of the
>transition.

>One of those things that PS can do that not many people know about.

>Good Luck

Bingo!  That's the trick that worked for me.  I tried
all sorts of tricks with cut/paste/selections and
feathering.  None of it worked.

The blending of layers works because one layer
will be dominated by shadows (in the unwanted
area) and the other layer dominated by highlight.

And there are no selections to make, hence, no
feathering issues.

Terrapin