Feature: The Colormancer Plugin shows color and exposure correction versatility
Idea: Comparison with other color change tools
I have been using the Colormancer plugin for the past past 6 weeks or so and I find that I am drawn toward using it more often than not. I explore here some of the reasons for this by comparing Colormancer with such tools as Photoshop's Curves and Exposure dialogs, Paint Shop Pro's Manual Color Correction, and Adobe's Lightroom. I also test the effectiveness of Colormancer in handling strongly underexposed and over-exposed images.

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The following underexposed image is the base for the first comparisons:

This image was taken at the Toronto Caribana festival and has been distinctly underexposed. Hence the first color correction tool I consider using is Photoshop's Exposure dialog. This tool allows one to correct exposure through Exposure, Gamma and Offset controls. Here is how Adobe defines each setting:
Exposure - Adjusts the highlight end of the tonal scale with minimal effect in the extreme shadows.
Offset - Darkens the shadows and midtones with minimal affect on the highlights.
Gamma - Adjusts the image gamma, using a simple power function.

The Exposure tool was developed for working with HDR 32 bit images in Photoshop but also works well with 8 and 16-bit images as in this case.

I particularly like this tool because of the ability to work either with the highlights (Exposure) or the midtones/shadows preferentially (Offset).

Then the Gamma correction works across the board on all pixels. However, to make this really punchy one needs to work also with the Saturation tool and or the Channel Mixer.

In effect, users must flit between 2-4 tools to get the exact color correction you want in Photoshop and most other photo editors. Lets see if Photoshop's Curves tool improves things.

Same original image processed with Photoshop' Curves dialog:

Here the results are indeed punchier but I could not get punchy without sacrificing subtle tones such as on the skin and face. In general Curves provides a wealth of exposure correction opportunity but at the price of some tonal ranges in the gamut.

So the next color tool I tried was Manual Color Correction in Corel's PaintShop Pro:

And from the shot above one can see why I like PaintShop Pro's Color correction tool because it allows me to make a hue as well as gray tone exposure correction at the same time. Even in this GIF rendering on can see retention of better skin tones (compare brows) while still delivering punch.

The next tool I tried was Adobe's Lightroom:

Here one has a wealth of color and exposure correction tools under the Develop mode of operation. I was able to correction for exposure using the Exposure, brightness, and Contrast slider controls. Then I corrected color tone using the Temperature, Clarity and Vibrance controls. This allowed me to restore immediately some of the warmth of the scene. Suffice it to say - Lightroom is a very powerful color and photo editing tool.

Last but not least I used Colormancer:

Colormancer works somewhat like Lightroom and Photoshop's Exposure - manipulating color bits selectively. Go here for the explanation. Also see, again despite the GIF screenshot, the much less contrasty skin tones in the brow of the man's face but still punchy colors in the costume and float.

Colormancer with Under and Overexposed Corrections

The next couple of tests show how well Colormancer can help when the image is badly under or over exposed. Lets look at overexposed because the color details washout in these circumstances and are hard to recover:
Colormancer correction on top half

I was surprised to see how much color and shading that Colormancer was able to restore while at the same time I was able to make Saturation and Luminosity corrections. True, it is not the same array of controls available in Lightroom, but I find that the corrections in Colormancer are more subtle and satisfying. Also, because Colormancer is an Adobe plugin I can apply corrections to a selected/masked portion of the image (just coming to partially to Lightroom 2). Weak and bleached out hues (except for the the sky rendered clorox-clean)were restored with out the loud blare of many Brightness/Contrast and Saturation correction tools.

The final test is the a case of deliberate 2-stop underexposure using the auto-bracketing feature of the new Casio Exilim camera:

Here Colormancer did amazingly well in the slit image of the crowd in the background but became a bit too punchy in the red along the folds and in the silver sparkle strips. But that may be camera based as the strips, even in the revealed original image exposure, are already contrasty.

Summary

I like using Colormancer for two reasons. First, its color corrections are more selective and subtle - not the linear response of most Brightness/Contrast and Saturation controls. Second, Colormancer, a bit like Lightroom, give a wide selection of controls: Brightness, Contrast, Saturation, and Luminosity which work selectively on the whole image. Bottom line - I find with Colormancer I arrive at challenging color and exposure corrections very quickly. Try it - I suspect you will like it too.