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Photoshop Elements >
High Pass & Gaussian Blur Filters
Compared with Step Wedges
High & Low Frequency
Image Information
Photographs contain high and low frequency image information.
The High Frequency - Low Frequency Step Wedge below has:
• High frequency image information to the left.
• Low frequency image information to the right.
An example of high frequency information is the eyelashes on a portrait.
In the same portrait, the white of the eye below the eyelashes has low frequency information.
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| High Frequency Image Information | Low Frequency Image Information |
| Such as Eyelashes | Such as the White of an Eye |
High Frequency - Low Frequency Step Wedge
High Pass Filter v. Gaussian Blur Filter
The High Pass and Gaussian Blur filters do the opposite of each other.
The High Pass filter allows high frequency image information to pass through.
Low frequency image information is blocked.
In contrast, the Gaussian Blur filter is a low pass filter.
The filter allows low frequency image information to pass through.
High frequency image information, where there's lots of detail, is blocked.
| Filter | High Frequency | Low Frequency |
| High Pass | Passes | Blocks |
| Gaussian Blur | Blocks | Passes |
Below, compare the HL Step Wedge, the HL Step Wedge with High Pass Filter Applied, and the HL Step Wedge with Gaussian Blur Filter Applied.
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| High Frequency Image Information | Low Frequency Image Information |
High Frequency - Low Frequency Step Wedge
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| High Frequency Image Information | Low Frequency Image Information |
High Frequency - Low Frequency Step Wedge
With High Pass Filter Applied (Radius: 10 px)
High frequency image information (detail) is passed.
Low frequency image information (little detail) is blocked.
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| High Frequency Image Information | Low Frequency Image Information |
High Frequency - Low Frequency Step Wedge
With Gaussian Blur Filter Applied
(Radius: 10 px)
High frequency image information (detail) is blocked.
Low frequency image information (little detail) is passed.