Adobe Photoshop is a powerful and flexible tool
for the professional. You can do almost anything with your images
with it… if you only knew how to use it!
Over time, I hope to add more Photoshop tips.
For now, we have only one on how to use the Unsharp Mask
feature to maximize your image sharpness.
New Technology Notes
Recently, a Photoshop "action" script called
Fractal Sharpen has become available. It does a much
better job than unsharp mask (but requires that you own a copy of
Genuine Fractals - which you need anyway to do resizes and
printing). The same company also offers another set of tools,
including one called Local Contrast. This is a very
powerful tool to make your image stand out when printed - it
recovers lost impact when going from display to paper.
What are you really doing when you are digitally
processing an image? There are a number of schools of thought
on that subject. Some believe you are changing it from a
photograph to a false view of reality. This is common among
"old timers" who have been using the darkroom and expensive
equipment and techniques with the camera to improve images.
They tend to believe that adjusting photographs digitally "ruins"
them. Well, you certainly CAN ruin images with your computer!
But really, the tools just got better.
My philosophy - boiled down to its basics - is
this: with digital image processing, I am able to recreate the
image as I saw it, with the emotion and power of the real world
image I experienced when I captured the image. While you can
do many amazing and fun things with Photoshop besides this, such as
composites and overlays, warping, etc., my real interest is using it
as a tool to recreate - as best as possible - the full impact and
glory of the original scene. Faithful recreation of the
emotional response is my goal.
Why does this work?
What few people realize is the most problematic
step in the entire photography process is the LAST step - printing
the image from the negative. The image on the negative has
much greater potential than you would ever realize by looking at a
standard analog print! The color space transforms used by
digital film scanners can extract incredibly accurate data from the
film, by taking advantage of deep knowledge of the film's response
characteristics to light. Effectively, and inverse transform
is applied to the data, to faithfully reconstruct as best as
possible the original scene. The result is that the digital
scan is actually a much more accurate representation of the image
then ever possible with analog methods. The result is - you
can get significantly better images by working with the digital data
than were ever possible in the analog darkroom days.
I prefer to work with high resolution images such
as those created by scanning film. The most available of these is
PhotoCD from Eastman Kodak. The
PhotoCD is greatly preferred over a similar product, PictureCD, because it is 4x the resolution.
sharpening tips provided herein are not applicable to digital
camera images because the images have already been heavily
processed in the camera. Each camera manufacturer does it
differently. Unfortunately, this means that different
approaches are required for each manufacturer's product to improve
sharpness. In some cases, it is too late - the image is
already heavily sharpened, and cannot tolerate additional
My favorite provider for PhotoCD at a reasonable
price is Dale Laboratories,
in Hollywood, Florida. Visit their web site for more information.
Resolution and CCD's
Images from a digital camera are typically created from an image
sensor (CCD) that uses a "Bayer" pattern of color filters, shown to
the right. Each pixel is actually only one color: red,
green, or blue. The green pixels take up 50% of the available
pixels, while blue and red take 25% each. The information
received from the CCD must then be "reconstructed" back to a full
RGB image. Thus, for a green pixel, blue and red must be
recreated from surrounding red and blue pixels, etc. This
pattern requires a "blur" filter in the lens system to prevent color
artifacts from the reconstruction process - further degrading the
sharpness of the image.
While there are some very good reconstruction
filters used today, the reconstructed image DOES NOT have the same
information content as a scanned 3-color image of the same
resolution. Thus, a 1 million pixel digital camera image is
NOT as good as a 1 million pixel film scan. A good rule of
thumb is to cut in half the digital camera pixel count when
comparing digital captured data with scanned data. Thus, a 6
million pixel PhotoCD image is about as good as a 12 million pixel
digital camera - assuming it uses a color filter array such as the
Bayer pattern. If 3 separate CCD's are used, then this 50%
factor no longer applies.
If there are enough pixels - or if you are not
interested in the fine detail, then this factor generally will not
matter too much. For fine photographic art or large nature
prints, however, this is a serious issue. Thus, I will stick
to PhotoCD and fine-grained film for a while longer - at least until
I can afford a 12 million pixel digital camera!
Taking it one step farther, you can get a "pro"
scan on PhotoCD with 4x more resolution - a 72MB image. This
will get you the absolute most resolution you can get off a 35 mm
negative. Alternatively, you can buy one of the "top of the
line" home film scanners, such as the Nikon Super CoolScan 4000
ED. This will give you even more detail in your images -
if you use good enough lenses and film!
Preparation: Color Management
Before you can start working with digital images
with reasonable expectations of results, you need to get your
workstation set up properly. Specifically, it is critical that the
effects you are adjusting on your CRT monitor are closely correlated
with the printed result (Do NOT under any circumstances use an LCD
Monitor for color work! The color fidelity is not even close).
There is no greater frustration than working for hours on an image,
getting it to look "just right" on the monitor, only to find that
the printed version does not look at all like you expected! I
recommend Monaco EZColor
Bundle as an inexpensive color
management solution. This system includes a monitor
colorimeter and a color "target" for you scanner. With this
system, you can calibrate your scanner, monitor, and printer all at
the same time. The results are impressive, indeed!
Color Space Issues
The CRT monitor works with RGB (Red, Green, Blue)
additive color space, while the typical printer works with CMYK
(Cyan, Magenta, Yellow, Black) subtractive color space. This means
that it is impossible to render some colors you can see on your
monitor on the printer (and vice versa). This is true even if
the printer was perfect - i.e., the only limitations were the color
space. In fact, typical printers can only print a fraction of
the theoretically available color space due to dye chemistry and
print technique limitations. However, you can come very close.
Ink Jet Printers
I find extremely satisfactory the incredible
prints you can get from the
Epson ink-jet printers. My current
printer is the Epson 1270. However, I strongly recommend the
Monaco EZColor solution to get the results you want from the
printer. Epson has moved on since I bought my printer, and has
added a number of impressive features.
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