Welcome to RC Filters!

Here is an overview of the plugins that I have made for Photoshop and compatible applications such as PhotoLine, PaintShop Pro, and IrfanView.  Each of them was made with specific goals in mind; I have pointed out the advantages of each plugin.  More information is available on the download pages.

New releases

The Very High Radius Contrast Mask and Very High Radius Shadows/Highlights filters were released in June 2019.  They use the same method for creating blurred masks as some of the other filters, and are suitable for images with linear dimensions of 10,000 pixels or more.

Version 1.202 of four of the filters (Very High Radius Unsharp Mask, Very High Radius High Pass Contrast, Adaptive Histogram EQ, and Adaptive Contrast Curve) were released in June 2019.  They have an improved shadows/highlights mask and some speed improvements.

Version 1.201 of eight of the filters were released in June 2018.  They have reduced memory requirements and should run better on larger images, with linear dimensions of 10,000 pixels or more.

Version 1.2 of each filter, and several new filters, were released in March 2018.

• General improvements include an improved progress bar, an HTML help file for each filter, and an active Shadows/Highlights control and blend ranges for the contrast-increasing filters.
• Fine USM Sharpen/Deblur has an improved edge mask, and improved interaction between the two sharpening methods.
• Four-channel separation now includes the option for six-channel adjustments.
• The “glamour blur” functionality of the Very High Radius Unsharp Mask filter is now its own filter, with more targeted controls and an edge mask.
• The Retinex filter now allows for independent adjustment of the luminosity and color components.
• Retinex and Very High Radius High Pass Contrast include bug fixes.

The filters were made with FilterMeister and run in Windows applications.  I have provided the source code and released them under the GNU General Public License; if someone wants to make Mac or Linux versions, that’s fine with me.

Can I run these filters on a Mac?  Or on Linux?  Yes . . . .

Each filter is available in 64-bit for most 64-bit applications, and 32-bit for most 32-bit applications (running in either Windows 32 or 64 bit).  They work for me in Photoshop CS2 and CS5, PhotoLine 21, PaintShop Pro 2018, and IrfanView 4, in Windows 7 and 10.  (Please note that IrfanView 64 bit uses only 32-bit filters.)


The Filters

1.  Filters that I use on most images:

Fine USM Sharpen/Deblur

img Plugin

Fine USM Sharpen/Deblur gives you full control over the unsharp masking and deconvolution processes, including halo elimination, luminosity mode, very high amounts, edge masking, and blend ranges.

Advantages:  dual-mode USM and deconvolution, halo control, and integrated edge masking.

Very High Radius Unsharp Mask


High-radius low-amount (HiRaLoAm) unsharp masking is a technique for increasing local contrast, or “clarity.”  The radius is large compared to that used for conventional sharpening, often an appreciable fraction of the overall image dimensions.

Advantages:  the plugin is able to use radii of thousands of pixels for very large images.  An active shadows/highlights control and blend ranges protect blown highlights and shadows.  Color Only mode can increase global color contrast.


2.  Filters for enhancing certain images:

Adaptive Histogram EQ


Histogram equalization attempts to evenly distribute values across an image’s histogram.  Unlike a simple levels adjustment, equalization tends to increase contrast in low-contrast areas, while doing the opposite in high-contrast areas.  Adaptive equalization samples the pixels in separate regions of the image and applies equalization locally.

Advantages:  smooth results; full color preservation.


Adaptive Contrast Curve


Adaptive Contrast Curve samples the pixels in separate regions of the image and applies a contrast curve centered on the local average.  It operates similarly to the Adaptive Histogram EQ filter, but uses an S-curve instead of histogram equalization.  It may be used to bring out texture or “grit.”

Advantages:  smooth results; full control of the s-curve.  An active shadows/highlights control and blend ranges protect blown highlights and shadows.


Very High Radius Contrast Mask

img Plugin

Contrast masking is a means of decreasing the overall contrast of an image while retaining detail.  It is performed by inverting a grayscale copy of the image and using Overlay blend mode.  A Gaussian blur may be applied to the mask to enhance detail.

Advantages:  the blur radius may be adjusted from less than 1 pixel for a sharpening effect, to 10% of the image diagonal which may be over 1000 pixels for very large images.  The Blend Range sliders enable the plugin to be used as a shadows/highlights filter.

Very High Radius Shadows/Highlights

img Plugin

Shadows/Highlights lightens and darkens the image’s shadows and highlights using masks.

Advantages:  the blur radius may be adjusted to up to 10% of the image diagonal, which may be over 1000 pixels for very large images.  The shadow, highlight, and midtone masks may be saved and used for more complicated adjustments in the image editor.

3.  Color filters; I use one of these on most images:
(Update—nowadays I usually use Photoline’s saturation and Lab curves.)

The Ultimate Hue/Saturation Plugin


The Ultimate Hue/Saturation Control adds a variable vibrance control to the familiar hue and saturation.  Adjustments may be made to up to six selectable color ranges as well as globally.  The chroma adjustment is a “smart saturation,” limited to the maximum for the color’s hue and luma.

Advantages:  curve-like adjustment of the vibrance; “smart saturation” will not change the hue or block oversaturated colors; three histograms for feedback about the results.


Channel Saturation


Channel Saturation allows you to adjust the chroma and vibrance of four or six opponent colors independently.  It is similar to using L*a*b* curves, but uses the YCbCr or YCbCgCr color space with RGB images.  It is useful for separating colors of low saturation, such as the tints of weathered wood; or closely-spaced colors, such as the greens of mixed foliage.

Advantages:  a simple parametric analog of L*a*b* curves, with a fixed center point so the white point does not change; global saturation and vibrance adjustments.


Saturation Mask



Saturation Mask converts an image according to one of a number of color models and extracts the saturation or chroma channel.  It then inverts the extracted image and applies auto levels to fully expand the range from black to white.  Use the image as a mask to convert a hue/saturation control to a custom vibrance control.

Advantages:  unique.  This was my first Photoshop plugin.  I had made a similar plugin for ImageJ but wanted to do the same thing in Photoshop.

4.  Filters for special situations:

Glamour Blur

img Plugin

Glamour blur is a technique for softening skin and creating a dream-like look.  It consists of overlaying the original image with a blurred copy of partial opacity.

Advantages:  the radius setting is independent of the actual image size; edge masking prevents blurring of details such as eyes.

Very High Radius High Pass Contrast


High-pass contrast enhancement requires two steps:  the creation of a high-pass filtered image, and the blending of this image with the original.  The Very High Radius High Pass Contrast filter gives you full control over the entire process.

Advantages:  able to use radii of thousands of pixels for very large images.  A number of different effects are possible depending on the choices made in each step.




Retinex image processing attempts to imitate the lightness and color perception of human vision.  It is best suited for rescuing underexposed or badly color balanced images, or for extracting detail for scientific or technical purposes.

Advantages:  unique.  Intuitive interface; a high degree of control over the process including independent adjustment of the luminosity and color components.  Blend ranges protect blown highlights and shadows.


RG Color


The RG or red-green color space is a color space that uses only two colors, red and green.  The plugin converts RGB images to RG, and facilitates a number of editing functions that may improve RG images, such as pre- and post-conversion saturation and hue adjustments, and two different image blends.

Advantages:  unique.  Selective red and green vibrance controls, hue limits, and a hue histogram.


Hue/Saturation Channels


Hue/Saturation Channels is a utilitarian filter intended to assist in the selection or masking process.

Advantages:  hue difference prevents the splitting of closely-spaced hues into black and white.

5.  Fun filters:

RGB Gamut — displays the RGB gamut in the YCbCr color space.


RGB Gamut Cuboid — displays the RGB gamut in the YCbCr color space as a rotating cuboid.


Can I run these filters on a Mac?  Or on Linux?

Yes, but you must do it in a Windows application.  PhotoLine is fully functional in Linux using Wine, and runs all the filters.  And I have now gotten it to work in OS X El Capitan using PhotoLine 19.51 and the Wine Development 1.9.17 package.  Instructions for OS X:

•  Download and install the Wine Development .pkg file.  I also installed the mono and gecko packages as prompted.  Prerequisite:  XQuartz 2.7.7 or above; I used 2.7.9.

•  Run the Windows PhotoLine installer .exe as usual.  After installation, the desktop links do not work; go to username/.wine/drive_c/Program Files/PhotoLine and create an alias to PhotoLine64.exe on the desktop.

•  Copy the 64-bit filters to the PhotoLine/Defaults/Plugins folder.  (And color profiles to the ICCProfiles folder if desired.)

•  Open the desktop alias with WineDevel.app, open an image, and run the filters (found under Filter — RC Filters).


The unregistered filters will save images up to 720 pixels in width and/or height.  Please purchase a registration key for $9.00 which unlocks all of the RC Filters.  Use either of the secure links below and I will e-mail you a text file (RCFKey.txt) to copy into your plugins folder.  Be sure to use a valid e-mail address (I don’t sell or give them away).  I check my e-mail for payment notifications every morning, Pacific time, and other random times; if you do not receive a key within one day it means I am in the hospital.  If you paid for any of the RC Filters before keys were used, email me and I will send you a key.  The filters come with a demo key; if properly installed, the dialog will say “Demo key” when you click the About button.  Questions . . . .

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The filters, the help files, and the registration key all go into the same folder.  It may help to make an RC Filters subfolder.  Each filter has a link back to the plugin folder on the About dialog for easy access.

Default locations for the filters include:
• C:\Program Files\PhotoLine\Defaults\Plug-ins
• C:\Program Files\Adobe\Adobe Photoshop CS5 (64 Bit)\Plug-ins
• C:\Program Files (x86)\Adobe\Adobe Photoshop CS5\Plug-ins
• C:\Program Files\Corel\Plugins
• C:\Program Files\IrfanView\Plugins\Plugins32\Adobe 8BF
• C:\Program Files (x86)\IrfanView\Plugins\Adobe 8BF

© 2023 by Russell Cottrell; released under the GNU General Public License.