Idaho Airships, Inc.

Gradient Maps can produce some very interesting effects. Given clever manipulations, including Transparency adjustments, Blending Modes, and their application in tandem with Filters to manipulate Layer Masks, Gradient Maps prove themselves to be extraordinarily controllable and powerful tools.

Simply search PS Help for “Gradient Map” to familiarize yourself with the fundamental nature of the tool. As usual, you’ll need to open an image and experiment to really understand what a Gradient Map does, but keep in mind that we are dealing with full color (8 or 16 bits in various working spaces) Gradients.

Scanned medium format aerial image of Idaho’s Bruneau Canyons in the dead of winter, 2001.

Gradient Mapping of the Bruneau Canyon image. A very interesting effect is achieved by reversing the Luminance wedge, remapping dark to light and vice-versa. Please consider that the reduction in resolution and conversion to sRGB has ravaged this image-in a high res, aRGB or greater image the presecribed, very saturated colors survive and accentuate microdetail.

Understanding that Gradient elements (composite color levels) are parsed for their application is important. It may be necessary to comprehend and be able to explain the actual machinery in certain, very rare forensic applications. Let’s avoid that mess here.

Gradient Maps may not be directly applied (in PS) to <8 bit anything, including Layer Masks. However, there are some clever ways around this limitation-consider the production of a separate Gradient Mapped document, then using Apply Image to adapt it as a Layer Mask. Frankly, most sophisticated Layer Masks should be processed as a standalone documents and archived discreetly anyway.

One common misunderstanding we’ll address first is that Gradient Maps are purely confied to preexisting Luminance-that is to say that they cannot be used to affect the Luminance, only the Hue of the target image or Layer. This argument is easily dismissed by generating a Gradient Map Adjustment Layer and changing its Blending Mode. There are some deeper, but nearly insignificant Luminance and perceptual effects (remember…I mentioned that their application is parsed), but they exceed reasonable use in image preparation.

Let’s cover some techniques for customizing Gradients and therefore Gradient Maps:

1. Transparency Controls.

This Gradient is constructed with Transparency keys (top row of controls above the Gradient preview) that are not necessarily positioned at the Gradient’s extremities. The selected Transparency key (partially grayed equivalent to the amount of Transparency) is located at “75%” (the percentile of the Gradient’s increasing Luminance range). At the selected point, the Gradient has an Opacity of 15%. The Transparency Smoothness (transitional graduation between controlling keys) is 60%. Gradients may be saved (as “.grd” files) or loaded as required, via automation (PS Actions or .js Scripts) if desired.

2. Hue Controls.

This Gradient is constructed with Hue keys (bottom row of controls below the Gradient preview) that are not necessarily positioned at the Gradient’s extremities. The selected Transparency key (the small triangle “crown” is colored in) is located at “78%” (the percentile of the Gradient’s increasing Luminance range). At the selected point, the Gradient has the hue of the indicated Key, which may be set in the PS Color Picker by double-clicking on the key itself. The Smoothness (transitional graduation between controlling keys) is 5%. Gradients may be saved (as “.grd” files) or loaded as required, via automation (Actions or .js Scripts) if desired.

There are many other ways that Gradients (whether intended for Gradient Mapping or not) may be customized, including:

• Selecting the Hue by specifying Color Wheel degrees (why does he keep bringing that up!?! Could it have something to do with triadic and tetradic productions?)
• Ensuring that if the Color selected will survive to output it does not violate the output gamut.
• Application as a Gradient Fill Layer so that it is amendable and can be subjected to Blending Mode, Transparency, and Layer Comp control.
• Applied as “Radial,” “Angle,” “Reflected,” et. al., or Transformed, Warped, Rendered, or subjected to Convolution Filters when desired.

Gradient Mapping may be accomplished using any of the above controls with the added (if compulsory) effect of the automatic remapping.

So, what are some some actual uses of Gradient Mapping that might be worth your invesigation-other than the obvious and simple? What about batch-processing the conversion of color to monochrome with a specified low key limit of 9 and high key limit of 224 (yeh, yeh…Channel Mixing and Output Levels…)? Conversion to DuoTone, TriTone or other multiple Hue derivatives while retaining control over individual Channels? Mapping in a gorgeous horizon glow against very detailed trees in which the leaves are blurred because of a long exposure on a windy evening?

L