APOGEE PHOTO MAGAZINE: Photoshop Tips - Changing Backgrounds and Adding Shadows

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Apogee Photo Magazine

Carl Volk's
Photoshop Tip of the Month

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

Carl's art, talents and teachings will live on for all of us to enjoy.
Visit: http://www.carlvolk.com

Carl Volk's Photoshop Tip of the Month

Changing Backgrounds and Adding Shadows

Carl Volk's
Photoshop Tip of the Month