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Hi Bruce,            I think the difference in Lightroom is that
it resets the colour balance, although it can't generally do that on
pure white. It needs a neutral grey. There is some way of doing that
(i.e. reset the colour balance with an eyedropper) in Photoshop but
it's complicated.Photoshop always changes the colour balance when you
alter contrast whether you use curves or not. It's a myth that curves
solve all these problems in PS. You can set up an action to copy the
background layer twice, fill the middle layer with 50% grey in "color"
mode, fill the top layer with 50% grey in 'luminosity" mode, then set
the blending mode of that top layer to "Color". You then have the tone
layer separated from the colour layer and can adjust tone without
major changes to colour. I know there are now LAB(?) settings that
might make this possible without doing this but I'm not sure they
really do.Cheers,Geoff

----- Original Message -----
From: "SciArt-L Discussion List-for Natural Science Illustration-" 
To:
Cc:
Sent:Tue, 11 Mar 2014 19:45:40 -0400
Subject:Re: [SCIART] Getting white backgrounds white. Sigh.

Geoff,

You can do the same thing in Photoshop by using the white dropper on a
curves adjustment layer.  Clicking that dropper on any value sets
that value to 255.  Karen Ackoff mentioned this earlier in this
thread.

Some use white and black and midtone droppers to set the general range
and contrast slope in photos.  I've always felt that trying to
estimate the "midtone" gray is haphazard at best.  Too, looking at
the histogram in a curves layer, one can easily find the black and
white limits of the image just by sliding either end of the curves
line up to that particular limit.  A move that may or may not be
advantageous to the appearance of the image in question.  I have,
however, occasionally used the black and white droppers when
converting RGB images to B/W.  For the most part I like to keep as
many options open when processing any image, photo or artwork, because
they're all different to begin with.

b

On Tue, Mar 11, 2014 at 6:15 PM, Geoff Thompson  wrote:
In Lightroom you can also click on a background paper to make it
white. I
 had to do this when photographing watercolours for a kids' book
illustration
 that had been done on very yellow paper. The designer wanted pure
colours.
 So I was able to deliver rich depth of colour with a pure white
background.
http://www.shop.qm.qld.gov.au/default/happy-birthday-muttaburrasaurus.html
[2]
http://www.shop.qm.qld.gov.au/default/where-s-your-teddy-muttaburrasaurus.ht
 ml
 Cheers,
 Geoff

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-- 
Bruce Bartrug
Nobleboro, Maine, USA
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The world is a dangerous place, not because of those who do evil, but
because of those who look on and do nothing.  - Albert Einstein  

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