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.

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.

 

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.

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