Sunday, September 21, 2014

Creating a Blue Sky with LAB Color and Curves

My tutorial on performing a LAB color channel swap can be found on YouTube.

If you like creating color infrared photographs, you already know how to perform a channel swap. The classic channel swap using the Photoshop Channel Mixer usually generates a blue sky that is the hallmark of “traditional” color infrared photos. Unfortunately, the channel mixer is a rather crude implement. When I use the channel mixer, I am often left with residual blue and grey areas (in clouds and concrete) that require extensive hue and white balance adjustments. As I make more and more adjustments to remove these colors, I end up generating color noise and halos that are frustrating to remove.

Enter the LAB color channel swap. In its simplest iteration, this procedure can produce a good quality channel swap in seconds. The procedure for the simplified channel swap is shown below. The simplified channel swap provides a good starting point for generating a blue sky for most color IR photos.  With a little more work, I can efficiently generate a blue (or green) sky, adjust the colors in defined areas of the image, and improve the contrast - all in one workspace. The LAB color process also minimizes color noise. The video link at the top of this post will take you to a video tutorial on how to do the LAB channel swap. The tutorial will also show you how to efficiently improve color and contrast by using LAB color curves. 

When I talk about LAB color, most photographer's eyes start to glaze over. For most us, the LAB color space is a “Never Never Land” - a poorly understood place that doesn't play nice with printers and plug-in programs. However, the infrared photographer is, by definition, an extremist who needs extreme tools to manipulate the data generated by their camera’s image processor. LAB color, with its wide gamut and the ability to manipulate luminance independently of the color information, is becoming, for me at least, the workspace of choice for processing color and black and white IR photographs.

Simplifed Channel Swap - LAB Color

Simplified Channel Swap Method
Change to Lab Color:  
   Image > Mode >Lab Color
Select Channels > A channel 
Click the “eyeball” next to Lab (at the top)
Image > Adjustments > Invert
Select B channel
Image> Adjustments > Invert
Image >Mode >RGB

If you want to follow along with the tutorial, you can download the lake image from the following website: 

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  1. Hi, No it was two years ago but only just found this and was most helpful. Thank You. Russ

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