Layer Modes & Blending Options
This lesson explores the use of Photoshop Layer Modes and Blending Options to achieve a startling improvement without the use of curves or other traditional color correction techniques.
The Raw Image
Here is a Jpeg from a digital camera capture of a California poppy field. Its an OK image as it is but it can be improved. The two most obvious problems are that the sky is overexposed and the landscape below the horizon is a bit drab and lifeless. In general the color is decent except for a bit of pink in the clouds. The following steps apply components of the image against itself to achieve all the necessary corrections and its best if we take carer of color deficiencies first before proceeding with contrast or saturation moves. The first step here will be to elliminate the pink cast in the clouds.
Create a Solid Color Adjustment Layer
Click on the New Adjustment Layer icon at the bottom of the Layrs palette and select "Solid Color"...
Make a neutral gray Solid Color Adjustment Layer
In the resulting dialog, click in the field of color and drag to the left to select a neutral gray color. This "Solid Color" will cover up the image but we will use it to neutralize the color of the clouds in the following steps. To isolate this gray color to just the clouds, we will take advantage of Blending Options...
Select Blending Options
Click on the layer options flyaway at the upper right of the Layers palette and select "Blending Options" from the menu. Normally we might change the layer apply mode to "Color" first but right now we will leave the mode at "Normal" to better illustrate how Blending Options work...
Layer Style dialog
Selecting "Blending Options" brings up the Layer Style dialog – at the moment, we're only interested in the "Blend If" area at the bottom of the dialog. The two gradients labeled "This Layer" and "Underlying Layer" can be used to control how the selected layer blends with the underlying layers. The gradients represent the tones of the image in that layer – each gradient has a white and black point slider that can be used to make light or dark portions of the image transparent. In our case, the top layer is all one shade of gray – we are going to use the "Underlying Layer" gradient to control how the solid gray layer is blended into the underlying image...
Change to the Red Channel
The default "Gray" represents the overall luminosity of the image in the various layers but you can also choose the tones from an individual channel by selecting from the drop down menu. The Red channel has the most contrast in the sky and, since that is where we want to concentrate our efforts, select "Red"...
Change the "Blend If" slider
Click and drag the black point slider in the "Underlying Layer" gradient to the right and watch how the image is revealed. All the darker tones to the left of the slider are being used to make the solid gray layer transparent in these areas. Continue dragging to the right until...
Isolate the gray to the clouds
... the only gray left is covering the clouds. At this point, the transition from image to solid gray is rather abrupt. To insure that the final correction is undetectable we have to make sure that this transition blends smoothly.
Split the slider
Hold down the "Option" or "Alt" keys and drag the two halves of the slider appart – this creates a transition across the tones to blend into the gray smoothly.
Change the "Blend Mode" to "Color"
Click on the "Blend Mode" drop down menu and select "Color" – the clouds will come back and the gray layer will be applied to the color thus eliminating the "pink" cast. Click on OK to dismiss the dialog.
Apply a gradient to the layer mask
There is a slite amount of gray "color" poluting the orange poppies. To eliminate the effects of the color neutralizing gray layer from the rest of the image, (1) select the gradient tool from the Tool palette. Make sure you have black as the foreground color, (2) click on the Gradient drop down in the Tool Options bar and select the "Foreground to Transparent" gradient. (3) Drag out a gradient at the horizon to mask off the flowers.
Duplicate the Image
Now we will move on to adjusting the saturation of the colors. This suggests a move in LAB color. At this point its a good idea to save-as and guarantee that we won't loose our work up to now. We will preserve this RGB document as it is so we can return to it later. After saving, select "Duplicate" from the Image menu to create a copy that we will convert to LAB.
Check "Duplicate Merged Layers Only"
To make the next step work properly we want to end up with a single layer. Checking "Duplicate Merged Layers Only" ensures that the result of the two layers will be duplicated into a single layer in the new document.
Duplicate layer and change apply mode to Overlay
We could use curves to adust saturation but there is another method that takes advantage of apply modes and Blending Options. (1) Duplicate the background layer by dragging the Background thumbnail to the new layer icon at the bottom of the Layers palette. (2) Click on the layer mode drop down and select Overlay...
Contrast and Saturation
Overlaying the image onto itself results in a huge boost in contrast and saturation. The effect is overwhelming and the additional contrast is unwelcome. To control the effect we will return to our friend Blending Options.
Blending Options Controls
There are a number of controls that are availble in Blending Options and the effect of these controls changes with different color modes. LAB separates luminosity from color by assigning it to its own channel. (1) We can turn off Overlay effect for the "L" channel by unchecking "L" – this eliminates the contrast enhancement and leaves us with only the added saturation in the colors. Right now the orange flowers and the blue sky have gotten a little too vivid! We can ramp-off the saturation in certain color ranges using the "Blend If" sliders in the "a" and "b" channels. (2) Split the white point slider in the "a" channel and move the left half over to the middle of the gradient. (3) Move the other half over until the flowers reach the saturation you like. (4) Split the black point slider in the "b" channel and move the right half over to the mid-point. (5) SLide the other half over until the sky gets to a good color.
Enhanced Color in LAB
The color is now a lot happier but we still have a bit of work to do. Save this document incase you need to return to make more changes. The next steps will need to be done in RGB so we will merge this version back into the original RGB as a layer. to do that, first...
Flatten Image
Select "Flatten Image" from the layer options flyaway at the upper right corner of the Layers palette...
Drag LAB document onto the RGB document
(1) Make sure you have the "Move Tool" selected in the Tool palette, then hold down the "shift" key and (2) drag the thumbnail or (3) click and drag from inside the LAB document window onto the original RGB document window.
Make a Channel Mixer Adjustment Layer
Now that we have some good color to work with we're going to adjust the contrast and value structure of the image. Right now the sky is too bright. After examining the individual RGB channels we can see that the Red channel has a much darker sky and nice contrast in the and clouds. We will apply the Red channel luminosity to the color image using the Channel Mixer. Make a new Channel Mixer adjustment layer by selecting from the New Adjustment Layer drop down at the bottom of the Layers palette.
Channel Mixer
The Channel Mixer allows us to "mix" channels to create various effects. By checking the Monochrome checkbox we can create a B+W effect using the luminosity of the RGB channels. For our purposes we simply want to apply the luminosity of the Red channel. This can easily be achieved by selecting one of the presets from the "Preset" drop down...
Select the Red Filter Preset
Select the "Black & White with Red Filter (RGB)" preset.
Red Channel Black & White
The Image now changes to B+W. We are going to use the luminosity of this B+W in the sky – click "OK" to dismiss the dialog and change the layer apply mode to...
Change Layer Apply Mode to Luminosity
Change the layer apply mode to "Luminosity"... the sky takes on the dramtic contrast of the red channel. The rest of the image is a little less ideal. We can limit the effect of the Red channel luminosity with, you guessed it, Blending Options...
Change Blending Options in Blue Channel
The Sky is mostly white and the foreground mostly dark in the blue channel so it is the best candidate for Blending Options. Move the black point slider to the right to remove the red channel luminosity effect from the flowers and grass.
Load Selection from Layer Mask
Now we're going to do something trick! The followiing steps are going to work on the contrast and value structure of the foreground. We'll start by making a selection for the foreground. Since we already have a useful mask in the 2nd layer lets load that as a selection. Hold down Option or Alt and click on the layer mask thumbnail – a "marchiing ants" selection is placed around the sky.
Inverse the Selection
Select "Inverse" from the "Select" menu – the marchiing ants now suround the foreground.
Make a New Channel Mixer Adjustment Layer
Make a new Channel Mixer Adjustment Layer by selecting from the Adjustment Layer drop down at the bottom of the Layers palette.
Select the "Green Filter" Preset
Select "Black & White with Green Filter (RGB)" from the Preset drop down – the foreground will turn into a grayscale rendition of the green channel. We will use this to adjust the contrast and the value rendering of the grass and flowers. Click "OK" to dismiss the dialog for nw – we will return to it in a moment.
Change Layer Mode to "Overlay"
The mostly gray green channel becomes a source of enhanced contrast when we select "Overlay" from the layer mode drop down.
Return to Channel Mixer and Adjust
At first the Overlay contrast makes the image too dark. Double click the "Channel Mixer" layer thumbnail to bring up the dialog again. We can bring up the value of the grass and introduce highlights into the flowers by pushing the "Green" slider to the right, past 100%. Keep the white in the smaller flowers from blowing out by subtracting "Blue" – move the Blue slider to the left. Under most circumstances we would strive to keep the "Total" mix at 100% but, in this case, we can violate this rule because we are applying the Channel Mixer in Overlay mode.
The Original Image
Hold down the "Option" or "Alt" key and click on the "eye" icon for the Background layer to turn off all the layers – Option/Alt click again to turn them all on again.
Congratulations! If you managed to follow along you learned about some pretty powerful features of Apply Modes and Blending Options. We've seen how to use Blending options to make portions of a layer transparent based on tonal values in an underlying layer. This has many implications for image correction work. We've achieved some very powerful enhancements using layer apply modes to increase saturation and contrast. We've seen the use of the Channel Mixer to apply grayscale channel information to the composite color image. The kind of local contrast developed through the use of the Channel Mixer in Overlay mode is impossible to achieve through curves. There is also a tremendous advantage over curves in that new values are directly calculated for each pixel in the image without stretching or posterizing tones – much stronger corrections are possible.