Reluminate 0.1

A PhotoShop plugin, developed using FilterMeister, that permits adjustment of luminance in color images, and serves as a simple channel mixer for controlling B&W conversion. The same thing can be accomplished by other means, for example the PhotoShop Channel Mixer & Layers, but I find this eliminates several steps and provides some flexibility that is inconvenient to use otherwise.

Up to Other Plugins

Background

The idea for this tool popped into my head after reading a raw conversion tutorial at Luminous Landscape.

Installation

Drop the filter (download below), which is an .8bf file, into your PhotoShop filters directory, usually something like c:\program files\Adobe\Photoshop\PlugIns\Filters. Then launch PhotoShop. I've tested this with Photoshop 5.0LE and CS, and PS Elements 2.0. It's not demanding and should work with other versions as well.

If you're using other software that accepts PhotoShop compatible plugins installation should be similar, but I don't have any examples to try. It might also run standalone with PluginCommander but I haven't tried that either.

Controls

Reluminate opens to a control dialog with a preview at left. You can drag on the preview to move around your image or selection. You can zoom using the +/- buttons below the image.

This filter is fairly fast - running the filter on a 2mpix image takes about 5 seconds on an old 450MHz P3.

Red/Green/Blue: Contribution of each channel to luminosity. Most color models have weights close to the defaults here - about 20% red, 70% green, 10% blue. Moving away from those values adjusts the color mix used to determine luminosity. Negative values effectively invert a channel: setting -20% blue will make bluer objects darker, for example. You can set these weights to any values you want, but it's generally helpful to ensure that they sum to something near 100 (or at least not 0); otherwise results can be unpredictable.
Brightness Adj: Adjustment to overall brightness.
Contrast: Overall contrast.
Saturation: Overall saturation. This may behave differently than the standard HSV saturation control due to the different color model. For example, when you desaturate (saturation = 0), the result is a black & white image with luminance according to the RGB mix chosen, rather than the flat-looking value image you get from HSV saturation.
Median Filter: When checked, Reluminate uses a median-filtered version of the image to make adjustments (but the original is still used as the basis for the final image, so little softening occurs). This can reduce noise that may become prominent when using a heavy blue channel contribution or making other extreme changes.
Show Clipping: Shows clipped highlights and shadows by inverting them (these will not show when the filter is executed).
Mode (Normal, Difference): Controls display of normal result or the difference between source and target images (the latter is for diagnostic purposes but could also be useful for creating adjustment layers).

Examples

The following examples illustrate the use of Reluminate. Your mileage may vary.

Original image: Inverting the red channel from 20 to -20 darkens the cones (they're still orange though) without much effect elsewhere:

Original image: One possible variation:

And another:

License

Reluminate includes absolutely no warranty express or implied - use at your own risk. Don't oversave your originals (duh).

Download

Sorry, there's only a Windows version: Reluminate 0.1

Feedback

I'm continuing to work on this out of my own curiousity. Rather than emailing me, please contribute to the Sony forum discussion at DPreview - otherwise I'll get too distracted from real work.

Original image:	Inverting the red channel from 20 to -20 darkens the cones (they're still orange though) without much effect elsewhere: