Changing Backgrounds and Adding Shadows
 A few years ago I was doing the ad photography for a grocery store
chain - all 4-color newspaper ads. The client wanted everything shot with
a black background - initially. After we had done about fifty shots said
client decided they wanted everything on a green background and asked,
"Can you please change the ones you already shot?" This is the process we
used.
The photo of grapes (top photo) was one of the first shots we did on
black. Fortunately, since the black background was of a uniform color and
density, I was able to use the Magic Wand tool to select it.* By setting
the Tolerance parameter to 12 (with anti-aliasing on) the entire black
background was auto-selected and the selection did not creep into the
darker areas of the red grapes. I then Feathered the selection one pixel
to insure getting a smooth edge. The selection was then saved as a
separate channel, creating the black and white mask on the left. Now we
can replace the background at will.
We then photographed some new shots on the new green background and
took some readings of the background top - a darker green because of the
lighting - and bottom (this was a digital photo project so we were
capturing right into Photoshop). Setting the foreground color with the
dark green at the top of the frame and the background color with the green
at the bottom of the frame, I was now able to simulate the new background
by using the Transitional tool (a.k.a. the Gradient tool), going from the
top edge to the bottom edge (with the shift key down to insure a perfectly
vertical transition). By Loading the selection mask we have previously
created and using the Transitional tool in its default set-up (Normal,
Linear, Dither on, Opacity 100%) the middle photo of the grapes was
created.
 Now we have to add a shadow to make our results look realistic. Since
the lighting was essentially soft overhead with some soft fill coming in
at about 45 degrees, I just wanted to add a very soft shadow. With the
background selection loaded, I first de-selected (command key down) the
entire top two-thirds of the frame using the Rectangular selection marquee
(no feathering). I then set the Lasso tool at 60 pixels Feathering (a 250
dpi file) and de-selected where I did not want the shadow to be - softly
edging out from below the plate, following the same curve as the plate and
the protruding grapes on the right edge. This new selection then, when
saved as a separate channel, is the black and white mask on the right.
Notice how soft the lower edge of the mask is yet the edge around the
plate is still completely defining. This is creating a selection that has
different amounts of feathering (1 and 60 pixels) in different parts of
it. With this selection loaded, the shadow is created by simply darkening
the area by adjusting Curves or Levels (or by using the
Brightness/Contrast adjustment) for the desired effect. Because of the
transitional mask effect below the plate, a soft and natural-looking
shadow is created.
 *If your original background is not a uniform
IN MEMORY OF CARL VOLK
=============================================================
>>>>Carl N. Volk<<<< April 8, 1953 - September 5,
2000
We would like to extend our deepest sympathy and
thoughts to
the family, friends and associates of Carl N. Volk, a writer
for Apogee Photo. He was a renowned photographer, a classical
guitarist, and a digital photography expert.
Apogee Photo would like our readers to continue to
benefit from
Carl's extraordinary talents. We will continue to place his monthly
Photoshop Tips in the Let's Get Digital section of the magazine.
If you feel you have benefited in anyway or would like
to honor
Carl, please consider CONTRIBUTING A DONATION.
The donated funds will assist in sudden family expenses,
in the
continuous maintenance of his website, and for the plans to
publish an anthology of his digital photographic works.
All donations are sincerely appreciated.
Please make checks payable to Claire Volk Heath:
Carl Volk Memorial Fund
c/o Claire Volk Heath
5057 Trail Lake Dr.
Plano, TX 75093
claire@heathtech.com
Carl's art, talents and teachings will live on for all
of us to enjoy.
Visit: http://www.carlvolk.com
(Starting Friday, October 27)
|
