Apr 27 2009
By: Rick Yaeger
This is a quick tip that will help greyscale images survive being printed in newspaper or run through a FAX machine. It utilizes a seldom used standard Photoshop filter called "High Pass".
What High Pass does is it isolates high-contrast image areas at a user specified pixel radius turning much of the image grey and leaving edge details untouched. The desired effect can be attained by adjusting the radius value — a setting of 100 will leave most images unaffected while a setting of 1 will turn an image almost entirely a monotone grey. Somewhere in the middle is a usefull filter waiting to be discovered.
Step 1: Bring your greyscale image into Photoshop and duplicate it on a second layer within the same document.
Step 2: Find the High Pass filter under Filter>Other>High Pass… and apply the filter at a setting of 10 pixels.
What you will be left with is an image that may resemble a screen shot from a ’50′s era television broadcast. Don’t worry, it won’t for long.
Step 3: Go to Image>Adjustments>Levels… and set the input levels to 0, 1.00, 128 and click Okay.
Now your duplicate layer should almost resemble a line art representation of the original.
Step 4: Change the layer blending options to "Multiply" from the layers pallette to apply this accentuated detail to the original.
Step 5: If you would like to compaire this image to the original, you need only click and unclick the layer visibility icon (the eye) next to the duplicated layer in the layers pallette. If you decide you like how this technique strengthens the detail of your image, go ahead and flatten the image and use it in your project.
This technique has also been known to work on color images but not nearly as consistlently successful as on greyscale.