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.

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.

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 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.

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.

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.

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 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 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.

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.

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.

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 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.