SF GrayMixer

Filter for versatile grayscale conversion following the channel mixer idea

The number one use of any channel mixer is grayscale conversion. Quality grayscale conversion takes into consideration that the human eye can perceive the same physical brightnesses differently (e.g. blue much darker than green or red). Furthermore, often different colors shall get different weightings when producing the grayscale version in order to enhance contrasts. This is all possible with a channel mixer using the monochrome option. SF Grayscale Mixer already comes with this mode built-in and therefore is easier to use than SF Channel Mixer. Moreover, there are additional functions like by-standard luminance conversion, the possibility of fixing a color and a clipping warning.

SF GrayMixer Pro

SF GrayMixer Pro

The GrayMixer is available in two different versions.

SF GrayMixer LE: The Freeware version gives you only the basic functionality of a channel mixer, but the auto balance function is built-in.

SF GrayMixer Pro 3.5: The new and full re-designed pro version has a comfortable graphical user interface (GUI) with 200% preview and functions for scrolling and navigating, 10 variation buttons and more (see here for more GUI details). This version is suitable for RGB, Lab and CMYK images with 8 and 16 bit color depth per channel.

Please note that the "basic" version (SF GrayMixer 2.1) is not longer available. If you own an old 2.1 version (basic or pro), you can upgrade to SF GrayMixer Pro here.

The download zip file includes two separate filters: a "normally" and a "scripting" version. You can install the version you wish or both. The license is valid for both. The scripting version is for use in a photoshop action or as a smart filter, the paramaters are saved in the action or in the smart object itself. But this version has some restrictions, e.g. the combination is not available (because of restrictions of the photoshop scripting interface).

Therefore an automatic version of the filter, which stores the parameters in a separate file, is also available (look here for details). This "auto" version works in the background without restrictions regarding variants and combinations, but cannot used as smart filter. Please download this version separatly.


SF GrayMixer Pro

SF GrayMixer Pro with image in CMYK color space

Features and operating instructions

The following explanations refer only to the filter-specific characteristics of SF GrayMixer Pro. The general functions of the SimpelFilter filters you find here.

A channel mixer with special features

The basis of the SF GrayMixer is similiar to the channel mixer (known from many imaging applications) in the monochrom mode. But the common channel mixers own some disadvantages (see here for details). SF GrayMixer eliminates this flaw and has some additional features.

Operating is easy, all options and settings are explained at the left margin.

Combining variants

The SF GrayMixer Pro supports up to 10 setting variants and allows saving and combining all variants. A mouse click in the combining check box switches the mode on and off. In the neighbouring combobox you have to choose the combining mode:

In the following modes the variants are applied separatly to the source image. The results are combined afterwards. All combined variant tabs are marked with red colors.

Darken: The minimum (darkest) value of all combined variants.

Lighten: The maximum (lightest) value of all combined variants.

Average: The average of the pixel tonal values of the combined variants.

Mix: The tonal values are mixed together. The result is similiar to the previous mode.

Neg. Mix: The mix of the inverted variants.

Multiply: The (normalized) tonal values are multiplied. The results are dark like the results of the Minimum mode.

Neg. Multiply: The inverted tonal values are multiplied.


Why a Grayscale Mixer?


A primary use for a channel mixer is grayscale conversion. With it, you can set the weightings for each of the RGB colors flowing into the grayscale image, precisely and optimized for each individual image. For producing grayscale images, Photoshop's and some other programs' channel mixers have a monochrome option. The figure to the right shows what it looks like if it is activated.

With the settings used in the screenshot only the information from the red channel is used at all. All the information from the green and blue channels is ignored. Therefore you can regard the conversion as a "red extraction" of the image. Generally though, you would add some parts of the green and blue channels and reduce the percentage of the red channel accordingly.

Doing this, you normally would have to be careful that the sum of all source channel percentages remains 100%. Otherwise, you would likely be ending up with blown-out highlights or plugged-up shadows (highlights and shadows being set to pure white or black, respectively) - in other words: you would experience clipping. Differences within highlight and shadow regions would therefore be lost.

This can be partially corrected using the "constant" slider, but only visually and not in an exact way. Furthermore, in Photoshop the slider is labeled misleadingly. It does not add or subtract a percentage of the given tonal value for the selected output channel, but always a fixed value instead. E.g. the setting +100% adds 255 to the tonal value of each pixel of the selected channel, +50% adds 127.

If for example the three color sliders are set in a way that their sum is 177%, it is not enough to set the "constant" slider to -77% to fulfill the 100% rule. This would subtract 196 tonal values from all pixels of the image not regarding their original values, plunging most images in deep shadows. Finding values by trial-and-error is no real solution either, because it is hardly possible to keep shadows and highlights intact at the same time. Because of this, the "constant" slider should not be used at all. Instead, slider values have to be addressed manually to preserve the sum of 100%, and this can be quite tiresome. SF GrayMixer from the SimpelFilter series avoids all of these disadvantages.

Of course you can also use SF ColorMixer with the gray option enabled to produce grayscale images. But SF GrayMixer makes this task a lot easier and more pleasant.


SF GrayMixer Pro 3.5

SF GrayMixer Pro auto

Without license the filter works as try-out-version. The try-out version has all the functionality of the licensed version, except that the filter applies watermarks to the image. In addition the maximum size of the filter dialog box is limited.

Please order the license key here.

SF GrayMixer LE

Plugin for Photoshop and compatible programs (Windows only). Version 1.1 from 9/1/2005.

SF GrayMixer LE is Freeware and can be copied and distributed freely as long as no charges are being taken.

Related Documents

The User interface page shows global functions and key shortcuts of the filters.

The Automation page shows how to use the filters in Photoshop actions and scripts.


(Full version)

Full support of 16 bit color depth
The filter works with RGB images of 8 and 16 bit color depth per channel. Internally the filter always uses 16 bit color depth.
Lab and CMYK support
Conversion by luminance
By standard, the weightings of the RGB colors flowing into the grayscale image are set to what I call "luminance mode". This conversion scheme, originally developed for television, corresponds very well to the way we perceive color brightness. Red flows into the brightness of the grayscale image by 30%, green by 59% and blue by 11%.
Auto Balance
Changing a slider will automatically re-adjust the output channel's other two sliders so that the sum of all three remains 100%. In order for this to work, the "lock" settings for all three sliders have to be unchecked.
Lock Option
The auto balance feature can be locked for each single slider ("lock" checkbox checked). If all three sliders are locked, like in the figure above for the red output channel, then their behavior is similar to Photoshop's.
Overflow Warning
If the sum of a triple of sliders differs from 100% this is displayed as an overflow (positive or negative). Such differences can occur if one or more sliders are locked or if one of the unlocked sliders is already at its limit.
Clicking with the right mouse button into the preview window fixes the current gray interpretation of the selected color. All following changes of the color sliders will not affect the fixed color. The surfaces of the two big buttons show the selected original gray and the fixed (resulting) gray and serve in addition for activating/deactivating and turning off the ColorFix function.
Clipping Alert
If this option is enabled image regions with tonal values of 0 (black) or 255 (white) will be displayed as blue or red. This allows for good visual evaluation of the current settings' effects on highlights and shadows of the image.
Brightness Slider (Gamma)
This additional slider modifies the overall brightness of the image. It changes the image's gamma value and therefore mainly the mid-tones, leaving black and white points untouched.
Combine Variants
You can combine up to ten variants easily into a single image. For combining you have the choice between seven blend modes.
Last Settings
The last applied settings are stored automatically and reloaded after restart. So you can work with up to ten favorite settings without manual reloading. Further you can store so many settings as you will in setting files.
Split Preview
Dividing the Preview window into two parts allows a Before/After comparison.
Choose Language
A mouse click changes the language between German and English.
Apply the filter automatically
You can use a special auto version of SF GrayMixer Pro from inside scripts and actions and therefore perform filters automatically on several images or whole folders. The settings are carried out conveniently in the Standard version of the filter.
Features not included in the LE version
Loadable/savable settings
Changeable window size
Comfortable navigation functions in the preview
Support for 16 bit files
Processing of images in Lab and CMYK mode