Screen Printing - February/March 2020 - 15

BACKGROUND REMOVAL FOR RIP PREPARATION
One of the most common reasons to edit out the background of an image for DTG printing is to prepare it for
RIP processing. Many of the more popular DTG machines
can require the removal of an image background (and
also any non-printing areas inside of the image) prior to
processing the image. This step ensures the RIP software
doesn't accidentally print the image background in addition
to the design.
To accomplish this step on an image, there are many
ways to extract it in Photoshop. Two of the most common
are to use the color range tool or the magic wand tool if
the background is consistent in color and/or value range.
You will have to practice with different selection settings
to dictate where the selection edges will stop related to the
closest variation in hue or value. If you set the fuzziness
too high then you may select colors that are beyond where
you want, and if it's too low then you may not get all of the
background. Sometimes you can use both tools together
and set the magic wand to 5 or 10 in the Photoshop property bar and slowly add to a selection in different areas.
This will often be faster than starting over and slowly
creating a path.
Before you create a path to extract a background, you
may want to try one or two other methods first. With an
image that has a very complex group of shapes, or a faded,
transparent, unclear edge between the foreground and
background, it can take an enormous amount of time to
create a decent background extraction path using the pen
tool. There are some other specific tools you can use in
Photoshop to shortcut this process if your background to
foreground edges are not as distinct (see Figure 2):
1. Try using one of the image channels. In the channel
dialog, choose one of the image channels that appears to
have the most contrast. Make a copy of this channel so it
becomes an alpha channel below. (It will say blue/copy,
for instance.)
2. Using this copied channel, you can then use the levels
or curves command to increase the contrast a degree
to see if you can get a better edge quality between the
foreground and the background.
3. Use the magic wand or quick selection tool to select the
background. Don't forget to add any additional negative
shapes using the "add" command (shape key).
4. Once you have selected the background you can then
inverse your selection and make the foreground area
solid black.
5. At this point, if you have to, you can go in and use the
burn, dodge, or other Photoshop tools to finish editing
your copied channel, which has now become a highcontrast mask.
6. Hold the control/command key and make a selection of
your mask, then go to your layers pallet and select/copy/
paste your foreground onto another layer.

7. Turn off the original image and add a layer below your
new layer and make it solid white or black to look at the
edges of your extracted image. Edit as necessary and
finalize your design.
You can use a similar process for a wide variety of images
where the background needs to be removed. Of course, there
are always exceptions when a much more detailed path or
mask must be created to properly extract everything, but the
goal is to do the least amount of detailed, time-consuming
work on production tasks.
REPLACING ONE BACKGROUND FOR ANOTHER
A common step in editing images is having to replace a background with another image or backdrop. Sometimes there are
things in the background that are distracting or the overall
image will look a lot better with another type of background,
so it's best to replace it.
The key to doing this step well is to consider several
attributes in the original image and source files properly
to make these specs before you try to start masking (see
Figure 3):
A. Depth of Field. If the original image had a very short
depth of field and the background is right up against
the foreground, it will probably be a good idea to find a
replacement background that's also close to the viewer.
If the depth of field doesn't match in the new background it can have a clearly "pasted on" look to the final
composition.
B. P
oint of view and horizon line. It's always a good
idea to find a source file for a new background that has
a similar point of view and horizon line than the original
file. If the original image was shot "worm's eye view"
from low to high and a background is swapped in from a
standing point of view, the result will look very awkward
and not mesh well.
C. Lighting direction and intensity. Find a source for a
new background that has the same location for a light
source and intensity as the original photo. Although it's
possible to change the lighting in an image, it's a very
time-consuming process and should be avoided if possible. This means if your original image was shot in the
early morning with the light behind the photographer,
you will want a similar light direction and angle in a
replacement background.
Once you've found a suitable background replacement for
your image, you can copy the new background layer behind
your masked out layer with your foreground elements, then
you can adjust the saturation, hue, and even blur it slightly to
create a realistic blending of elements.
BACKGROUND MASKING FOR COMPOSITION
When you're masking out a background for a composition,
FEBRUARY / MARCH 2020

Screen Printing - February/March 2020

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