Once you have your image saved on the computer, you can manipulate
it in an image editing program such as Adobe Photoshop®. As you
are working on your images, you should keep them in RGB, some filters
don't work in CMYK and switching back and forth between RGB and CMYK
loses valuable color information that you can't get back. Convert
to CMYK the last thing you do.
When working with color, use the neutral gray pasteboard around your
image. If you have your computers wallpaper, or desktop in view while
working on your images, the color perception of your image will be
You can edit the entire image or make a selection to edit only a
part of the image. The easiest way to make a selection is to use the
Marquee Tool, which restricts the selection to either rectangular
or circular. Other options for making a selection are to use the magic
wand tool to select a specific color, the lasso tool to draw a freehand
selection, or to use the pen tool. You can use the pen tool to create
a path which, after it has been saved, can be activated at any time.
The magnetic pen tool allows you to draw a path around an
existing image and the path will snap to the edges of the
area you are tracing. You will have to experiment with the
settings to get the best result. Save the path and you can
select it at any time to make it a selection.
Steps to adjust your image:
Calibrate your system
The most critical part to any color work on any system is to make
sure everything is calibrated. Otherwise the image on the screen could
look totally different once it is printed. You need to calibrate your
system often to ensure that what you see on your screen will be the
same on the printed product. For more information see color
You want to make sure your scan has enough color information to produce
a high-quality image. The higher the number of pixels in an area,
the greater the detail. Bad photos to begin with or bad scans may
be impossible to correct.
Note: When working on your images,
you should make a copy or use an adjustment layer so you can
always revert back to the original.
can check the histogram located under the Image menu in Photoshop.
The histogram shows the number of pixels at each brightness level
in an image. It also shows if there is enough detail to make a good
correction and gives a quick picture of the tonal range of the image.
If there are white gaps instead of solid black, there is missing data.
Highlights, Shadows and Midtones
There are several different ways to set your highlights,
shadows, and midtones. You can use either the Levels palette or the
Curves palette, whichever you prefer. The first thing to do is to
set the white and black (highlight and shadow) points and then adjust
set the highlight and shadow, use the eyedropper tools available in
either the Levels or the Curves palettes. First double-click the highlight
dropper (white one on the right) and set what color you want your
highlight to be. Then pick the lightest point in your image by looking
at the Info palette. Next, double-click on the shadow dropper (on
the left) and change the settings there. Then, pick the darkest point
in your image. If you do not know what values to use, ask your print
provider what they suggest. Typically for printing an average image
on white paper, you want to set the highlights for CMYK to the values
of 5, 3, 3, 0; or RGB values to 244, 244, 244; or grayscale to 4%.
Set the shadows values for CMYK to 65, 53, 51, and 95; or RGB to 10,
10, 10; or grayscale to 95%.
Another way is to use the Levels palette. You slide the highlight
end point (right side of the histogram) to the left or the shadow
end point (left side) to the right, or slide the middle one either
direction to adjust the midtones.
One more way to set the highlight and shadows is through the Curves
menu. Here you adjust the curve until it is the color you want.
Once you have the highlight and shadow points set, the midtones should
be fine. If you still need to adjust it, you can use either the Levels
palette or Curves palette. In the Levels palette, slide the middle
triangle to adjust the midtones until correct. You may also add up
to 14 points on the grid in order to adjust any other tones in the
image. Shown below is the Curves palette used to lighten the midtones
while working in RGB mode.
When editing the color of your images, you should be watching
the values in the info palette rather than depending on the
color of your monitor. It takes experience to learn what the
correct values for a specific color are, but it is much more
reliable than going by the colors shown on your monitor.
The clone tool can be used to air brush out parts of the image that
you want to get rid of or to duplicate parts of the image. Pick the
rubber stamp tool (or clone tool). Hold down the option key and click
the area where you want to duplicate. Then click in the area where
you want to do the painting and either keep clicking the mouse button
or hold and drag, whichever gives you the best results for the type
of image you are working with.
Filters are applied to bitmapped images to
create special effects. Some filters come with the image editing programs,
or there are a lot of third-party filters that can be added. Here
are some samples of some of the filters
available in Adobe Photoshop.
Chalk & Charcoal
Before you start to make changes in the image size box, make sure
to check the Constrain Proportions check box. The chain link next
to the width and height boxes also refers to being in proportion.
If don't want to scale proportionately, uncheck the box, but remember
you will be distorting the image.
If you know the percentage that you want to change the image rather
than the size, click on the drop down boxes next to the sizes and
change it to percentage.
Before you scale the image, you should understand resampling. When
you change an image's file size, the software automatically adds or
subtracts pixels in your image. Changing the image's file size is
called resampling. If you decrease the dimensions of your image size,
pixels are subtracted; if you increase the image size, pixels are
added. When pixels are added, they are interpolated, a process where
the software adds more pixels and then colors them with the average
color of surrounding pixels. Interpolating can result in a somewhat
blurred or fuzzy image.
There are three possible methods of resampling. The default is Bicubic,
which is the best possible method, but is also the slowest. It attempts
to improve contrast while interpolating. Nearest Neighbor is the fastest
but least exact interpolation method. If you use the Nearest Neighbor
method, your image will probably look jagged after rotating or other
manipulation. Bilinear is in between Bicubic and Nearest Neighbor.
With resampling checked...
- If you decrease the Print Size, the image file size and the number
of pixels in the image also decrease. The Resolution setting does
- If you increase the Print Size, the file size grows and the number
of pixels in the image increases. The Resolution setting does not
- If you decrease the Resolution, the file size decreases. The Print
Size does not change, but the number of pixels in the image decreases.
- If you increase the Resolution, the file size increases. The Print
Size does not change, but the number of pixels in the image increases.
If you want to change the Resolution or the Print Size without resampling,
uncheck the Resample Image check box. Without resampling, if you change
the Print Size dimensions the resolution will also change, or by changing
the resolution, the Print Size will also be changed.
With resampling unchecked...
- If you decrease the Print Size, the file size does not change.
The Resolution setting increases.
- If you increase the Print Size, the file size does not change.
The Resolution setting decreases.
- If you decrease the Resolution, the file size does not change.
The Print Size is increased.
- If you increase the Resolution, the file size does not change.
The Print Size is decreased.
Note: If you reduce your file size
(resample down) and then later enlarge it back up, the final
image will not be as sharp as the original. When the image
is reduced, the pixels are removed and when it gets enlarged,
it has to interpolate and cannot add back the original pixels.
Unsharp Mask (USM)
Unsharp masking is the last thing that should be performed on an
image. Always save a copy of the file before peforming the unsharp
masking step. It is hard to judge the outcome of unsharp masking on
the monitor. You will need to do a proof to see the final results.
- Amount - Amount determines how much to increase the contrast of
pixels, how much darker and how much lighter the edge borders become.
The amount entered can be from 1-500 percent, with the greater the
number, the greater the sharpening. High-resolution images require
a higher percentage. Using 150-300% usually provides good results
with high-resolution images.
- Radius - Radius specifies the distance out from the transitional
edge that you want sharpened. A lower value sharpening occurs closer
to the image edges, a higher value sharpens a wider band of pixels.
The suggested value for high-resolution images is between 1 and
2. Small detail such as human faces can tolerate the least amount,
or else any lines and wrinkles would be more exaggerated.
Large objects with large detail can use the most, and landscapes
are somewhere in between.
- Threshold - The threshold value determines how much contrast there
need to be in order for it to be considered an edge. Lower numbers
sharpen more because fewer areas are excluded. The default 0 sharpens
all pixels in the image. Higher values exclude areas of lower contrast.
Note: If your colors
in your image change as you apply the Unsharp Mask filter,
convert your image to Lab Color mode and apply the filter
to the L channel. The L channel is a luminosity channel, not
a color channel, so the sharpening will not change colors
in the image.
Color is affected by the type of light in which it is viewed. Different
lighting conditions will change the appearance of the color on a proof.
For example, the colors on a proof will look different under fluorescent
lighting than when viewed under sunlight. The colors surrounding the
proof will also affect the colors of the proof. Standard viewing conditions
have been established within the graphic arts industry because of
the affect that different lighting has on viewing colors. In order
to accurately view color, a color viewing booth is a necessary item.
A proper booth should use 5000 degree Kelvin lighting (standard daylight)
with equal color temperatures in each part of the spectrum, and no
reflections from surrounding surfaces.
Click here for more information on proofing