Breaking NEWz you can UzE...
compiled by Jon Stimac
'Enough Evidence' for Lotz Trial to Proceed –
INDEPENDENT ONLINE, So AFRICA - Aug 8, 2007
...defense advocate asked for a postponement to allow for two foreign
fingerprint experts to travel...
Fingerprining Snares Visa Cheats
2007 ...more than 6,000 potential
immigration cheats have been identified by a new plan to fingerprint
LOGAN DAILY NEWS, OH
2007 ...Municipal court judge purchases equipment for
office and sheriff's department...
British Man Seeks Clemency for Murders
MIAMI HERALD, FL
- Aug 9, 2007
...fingerprints on plastic wrap used to tie one of the victims and
other evidence that he owned a handgun...
Recent CLPEX Posting Activity
containing new posts
Moderated by Steve Everist
Subpoena the Verifiers
sharon cook 168 Sun Aug 12, 2007 7:46 pm
John's Quote about Confidence and Probabilities
g. 5394 Sun Aug 12, 2007 7:01 pm
Scotland in September
Ernie Hamm 584 Sun Aug 12, 2007 3:04 am
The Lockerbie Connection.
Iain McKie 14492 Sat Aug 11, 2007 9:07 pm
New book for Photoshop users.
Andrew Schriever 263 Wed Aug 08, 2007 5:53 pm
Statistics and Misidentifications - The weeks Detail
Michele Triplett 15581 Tue Aug 07, 2007 11:25 pm
Fingerprint Society Seminar - November
fpsociety 277 Tue Aug 07, 2007 8:48 pm
Footprint (Friction Ridge) Comparison
Charles Parker 269 Mon Aug 06, 2007 11:03 am
UPDATES ON CLPEX.com
No major updates on the site this week.
we looked at the new re-certification guidelines
for many of the IAI disciplines.
Andrew Schriever and Casey
Caudle bring us a look at efficient workflow techniques for detailed color
space examination. Their workshop was one of the more helpful ones I
attended at the IAI conference in San Diego and I was happy that they
accepted the invitation to pass on a few very helpful Photoshop tips.
Channel Splitting for
by Andrew Schriever, CLPE; and Casey Caudle, CFVA
Target Assets Protection Forensic Laboratory
faced with many difficult challenges when processing digital images.
Digital images contain both useful and distracting information. The
distracting information may be caused by color interference, repetitive
patterns and blur. Many of these challenges can be identified through a
careful analysis of each image. For image processing to achieve optimal
results, the analysis phase is imperative.
This article will focus on establishing a method to analyze color images
prior to applying specific filters or processes. In particular, this
article describes channel splitting. Channel splitting is useful to examine
the contents of individual color channels within an image and allows you to
analyze an image so that its colors can be later isolated.
Often, it is effective to see each color channel of an image displayed
side-by-side. This allows you to determine which channel(s) are
contributing the most information to the detail you are interested in. You
can focus on what is important while quickly identifying the distracting
information – such as the ridges of a fingerprint in one color channel & the
distracting noise or pattern in another color channel.
Analyzing an image by splitting color channels allows examiners to make
informed choices about the most effective color space and color isolation
technique for a particular image. Color isolation allows one to maximize
the clarity of identifying characteristics and reduces other distracting
color information. There are many other ways to isolate specific colors in
Adobe Photoshop including channel mixer, calculations, hue & saturation and
even working solely on one color channel.
The most common
color spaces native to Photoshop are RGB (red, green, blue), CMYK (cyan,
magenta, yellow, black), L*a*b (lightness, a, b).
First open an image in Photoshop then create a duplicate of that image
(Image -> Duplicate), and perform your channel splitting process on the
duplicate. Open the Channels palette by clicking on the tab labeled
“Channels”. If you can’t find the Channels tab on your Photoshop screen,
click on the “Window” menu at the top of Photoshop and make sure that there
is a checkmark to the left of “Channels”.
Depending on the color space of the image you opened, you will see the
different color channels present in the Channels Palette (CMYK for this
image). You can view the information that the individual color channels are
contributing to the image by simply clicking on the individual channels
(note – click on the small thumbnail image or the name of the channel).
the individual color channels for another color space convert the image to
the desired color space (Image ->Mode->RGB/CMYK/Lab). The individual color
channels for whichever color space you selected will be visible in the
Channels Palette. Each color channel will display a small thumbnail image
of the color channel and the name of that particular channel.
You can view each color channel as a separate image by using the “Split
Channels” function. Open the fly-out menu on the Channels Palette by
clicking on the circle button with the arrow in it (located directly below
the red x).
The third option from the bottom is “Split Channels”.
click on the “Split Channels” function, Photoshop will open new images.
Each image displays the information from one color channel. The name of
each image will be appended with a letter denoting which color channel that
image is displaying.
above graphic shows an image that was in the CMYK color space and the split
channels function performed. You can see that Photoshop split the original
image into 4 new images, each image displaying one color channel. Circled
in red is the portion of the image name that denotes which color channel
each particular image is displaying (K for black, Y for yellow, M for
Magenta, C for Cyan).
To view the images side-by-side, click on Window -> Arrange -> Tile
Horizontally. This will arrange all open images on the screen.
ensure that all images are displayed at the same magnification and position,
go to Window -> Arrange -> Match Zoom and Location. The Hand Tool and the
Zoom Tool can be configured to allow you to zoom and scroll all images at
the same time. Select the “Hand Tool” (keyboard shortcut H) from the Tool
Bar and check the box next to “Scroll All Windows” near the top of the
screen. Next select the “Zoom Tool” (keyboard shortcut Z) from the Tool
Bar, and check the box next to “Zoom All Windows”.
Note: Activate the Zoom tool (Z) and click anywhere within one of the
images to zoom in on all images. Hold the Alt key and click inside an image
to zoom out of all images. Press and hold the space bar and drag within any
one of the images to scroll all images to the same position.
This process can be performed in all available color spaces at once. To
view all 10 channels (R, G, B, C, M, Y, K, L, A, B) at the same time; open
an image, make 3 duplicates, convert each one to a different color space,
and perform the split channels function on each duplicate. This will allow
you to see every available color channel as an individual image and you can
view them side-by-side by tiling the images and locking the zoom and scroll
functions as described above. This can take up a lot of screen real estate,
so it is a good idea to press the “Tab” key before tiling the images on the
screen. Pressing the “Tab” key will hide all palettes and the tool bar from
view, allowing the images to fill the entire screen.
Automation of the process
users to automate many processes through the use of actions and scripts.
Users can create a custom action or script to automate the channel splitting
process, based upon their individual needs. We have supplied clpex.com with
a set of custom actions that automates the channel splitting process.
action in the Split Channels set is Color Channels. This automates the
processes described above creating a separate image for each color channel.
The user can run this action on an image, and then tile the images for
The second action, Channel Preview, will allow you to view all the color
channels from all the color spaces available (including desaturation and
grayscale conversion) in the channels palette of one image. (as illustrated
the action by right-clicking on the link below and choosing "Save target as"
Save it to the following location on the computer with Adobe Photoshop:
C:\Program Files\Adobe\Adobe Photoshop CS2\Presets\Photoshop Actions
If a different version of Photoshop is being used, replace the CS2 portion
of the path with the version number that is currently installed.
Do the same procedure on this
Image link for an image to download and practice channel splitting.
Select the fly-out menu in the actions palette and select load actions.
Navigate to the new action set named “Split Channels”.
G. Reis, (2007).
Photoshop CS3 for Forensics Professionals, Sybex Publishing, San Francisco,
J. C Russ, (2002). The Image Processing Hand Book, Fourth Edition, CRC
Press, Boca Raton, FL.
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