Applying Levels, Curves, Hue/Saturation, and the other adjustments as adjustment layers offers tremendous flexibility and power, but it isn't always the quickest or easiest way to fix your images. Also, while these tools are powerful (and essential to learn), they don't really relate to anything we did in the wet darkroomthey're much more akin to the controls on prepress scanners than to anything photographic.
The layer blending modes open up an entirely different way to edit images. Bruce likens use of the blending modes to making the images edit themselveshe actually spent the best part of a year eschewing the use of Curves layers as anything except a means of applying blending modes, just to see how far he could take this approach.
He concluded that Curves is indeed an indispensable tool, but nowadays he's more likely to use it as a fine-tuning tool, doing the heavy lifting with blending modes.
Using Layer Blending Modes
When we started our blending mode experiments, we duplicated the Background layer, and applied the blending mode to the duplicate layer. We quickly found that we could obtain the same result by applying an adjustment layerany kind of adjustment layerwithout making any adjustments, and setting the blending mode of the adjustment layer rather than duplicating a pixel layer.
We quickly settled on using Curves layers to do thisLevels layers take longer to create because Photoshop has to build the histogram that appears in the Levels dialog box, and if we need to make actual adjustments, more often than not we need to do so with Curves. Applying blending modes with Curves layers offers three advantages over doing so with pixel layers.
Before looking at actual examples, though, it's time to get your head around just what the blending modes do. They're sometimes referred to as "procedural blends" because they all use some arithmetical formula to calculate pixel values based on the values in the overlying and underlying layer. (Of course, when we use adjustment layers without making actual adjustments, the overlying and underlying pixel values are the same, which actually makes things a little simpler to understand.)
Layer Blending Modes
The previous examples were relatively simple, using straightforward adjustment layers for global editing, with some painting on the layer mask for local corrections. However, when you combine adjustment layers with the power of blending modes, you open up a whole new world of possibilities.
One advantage of using blending modes rather than simply stretching and squeezing the bits with Levels and Curves is that blending interpolates tonal values, producing smoother results. We'll show you some examples of how we use some of the blendng modes, but we encourage you to experimentthere are plenty of new techniques waiting to be discovered.
The blending modes are arranged in logical groups, according to the way they function.
Layer Blending in Practice
If the preceding discussion has rendered you crosseyed, some less-abstract examples may be helpful. The blending modes we tend to use most are Multiply to build density, Screen to reduce it, Soft Light and Hard Light to increase contrast, Color to change color balance without affecting luminosity, and Luminosity to sharpen images without introducing color fringes (we discuss sharpening layers in much greater detail in Chapter 9, Sharpeness, Detail, and Noise Reduction).
Tip: Stop-Based Corrections with Multiply and Screen
If you're more comfortable thinking in terms of f-stops than in levels or percentages, thank our friend and colleague Jeff Schewe for this insight. You can lighten and darken shadows by 1 stop by applying Screen and Multiply, respectively, at an opacity of 38 percent.
For a half-stop adjustment, use 19 percent. For a one-third stop, 13 percent seems to be slightly closer than 12, and for a quarter stop, 9 percent is the magic number. Multiply and Screen always affect the shadows more than the midtones and highlights, so the analogy with f-stops isn't perfect, but it's still a useful rule of thumb.
The practical examples that follow don't pretend to exhaust the power of blending modes. They're simply illustrative examples that we hope will fire your imagination and pique your curiosity. Rememberone of the huge benefits of working with layers is that you can't do any harm until you flatten the image, so feel free to experiment. Photoshop offers many ways to produce similar if not identical results, and we each find methods that work for us.
Building density with Multiply
The best analogy we've found for Multiply mode is that it's like sandwiching two negatives in an enlarger. Mathematically, Multiply takes two values, multiplies them by each other, and divides by 255. Practically speaking, this means the result is always darker than either of the sources.
If a pixel is black in the base image, the result after applying an adjustment layer with Multiply is also black. If a pixel is white in the base image, the adjustment layer has no effect (white is the neutral color for Multiply). We use Multiply with Curves adjustment layers to build density, particularly in the highlights and midtones of washed-out images like the one in Figure 7-18.
Figure 7-18. Building density with Multiply
This image represents a scene with a huge dynamic rangea backlit boat against the sun rising over the Gangesand thanks partly to the wonders of modern color negative film, partly to the filtration effect of the omnipresent smoke from the burning ghats, we were able to capture it. Our scan has detail in both the brightest part of the sun and in the darkest part of the boat, but the distribution of the midtones is quite wrongthey're much too light, rendering a potentially dramatic image merely pleasant. We can improve it very quickly with a single Curves adjustment layer, using the Multiply mode.
We create a new Curves adjustment layer, making no changes to the curve, and set the blend mode to Multiply by choosing it from the blend mode menu in the Layers palette. This is equivalent to duplicating the Background layer on top of itself and changing the new layer's blending mode to Multiply (see Figure 7-18).
Adding Contrast with Hard Light
We use Soft Light, Hard Light, and Overlay to build contrast (since the overlying and underlying pixels are identical, Hard Light and Overlay produce exactly the same result). We use Soft Light for smaller contrast boosts, and Hard Light or Overlay for stronger ones. All three blend modes preserve white, black, and midlevel gray, while lightening pixels lighter than midlevel gray and darkening those that are darker. Figure 7-19 shows a contrast adjustment with hard light.
Figure 7-19. Increasing contrast with Hard Light
Adjusting color balance with Color
While we sometimes use Photo Filter adjustment layers for warming and cooling effects, we find that Solid Color layers set to Color blending with a low opacity offer more controlwe can tweak the color by double-clicking on the layer without having to tunnel through the Photo Filter dialog box.
We start out by creating a Solid Color layer of approximately the color we want, then we reduce the opacity, typically to around 1020 percent. Then we fine-tune the color to get the result we wantwe usually tweak the Hue and Saturation fields of the Color Picker by placing the cursor in them and pressing the up and down arrows on the keyboard.
Figure 7-20 shows the process and the result of adding a Solid Color layer. We started out by picking the approximate colorthe image is a little green, so we picked its opposite, magentathen we used the color picker to fine-tune the solid color to get the result we wanted. Now the edited image does a much better job of conveying the oppressive heat, the omnipresent smoke and dust, and the languor of the millennia-old ritual that takes place at dawn on the Ganges.
Figure 7-20. Adjusting color balance with Color
Opening shadows with Screen
Screen is literally the inverse of Multiply. The best real-world analogy we've heard comes from Adobe's Russell Brown. Screen is like projecting two slides on the same screen. The result is always lighter than either of the two sources.
If a pixel is white in the base image, the result is white, and if it's black in the base image, the result is also black (black is the neutral color for Screen). Intermediate tones get lighter. We often use Screen to open up dark shadows.
If you're a techno-dweeb like we are, you probably want to know what Screen does behind the scenes. Photoshop inverts the two numbers (subtracts them from 255) before doing a Multiply calculation (multiplies them by each other and divides by 255); then the program subtracts the result from 255. That's it. Now, don't you feel better knowing that?
Bruce shot the image in Figure 7-21 from his deck, using a Canon EOS 1Ds, on a typically foggy San Francisco late afternoon. The image holds detail in both highlight and shadow, but the foreground is dark and muddy, an ideal candidate for opening up with Screen blending. We want to preserve the dark sky and hold the detail on the sunlit buildings across the bay, so we'll make the adjustment, then localize it using the layer mask.
Figure 7-21. Opening shadows with Screen
Creating the mask
We could get a pretty good result by painting with a large soft-edged brush, but we found we could do even better by first making a marquee selection that covered the dark sky, filling the selection with black on the layer mask, and then making a second marquee selection on the bright area, and refining it with Color Range, as shown in Figure 7-22.
Figure 7-22. Building the layer mask
Complex Layer Blending
The preceding examples were relatively simple. While we always look for simple fixes, some images entail more complexity than others. The image in Figure 7-23 is a hardy perennial that we nevertheless continue to improve as both the tools and our understanding of them evolves.
Figure 7-23. An image with many problems
This image has more than its share of problemsit's shot into the sun on color negative, and the scan is flat with a greenish color castbut as is often the case in the real world, reshooting isn't an option!
One of our rules of thumb is to fix the biggest problem first, but in this case it's a toss-up as to whether the color or the contrast is the worse issue. Since we really dislike looking at green people, we'll address the color cast first, then the contrast hole caused by the lens flare, then the overall contrast and color balance. We won't be attempting perfection in the first round of editswe're just putting building blocks in place that we'll tweak later.
Figure 7-24 shows our first stab at the color cast. When dealing with color casts, we usually try Auto Color's Find Dark and Light Colors with Snap Neutral Midtone, perhaps with manual adjustment of the target midtone color, but in this case it didn't do anything useful, so we applied a solid Color Fill layer with a purplish-magenta color, Color blend mode, and an opacity of 19 percent. The cast seemed stronger on the right side of the image than on the left, so we made a gradient fill in the layer mask from white to 25 percent gray.
Figure 7-24. Addressing the color cast
Our next step was to fix the contrast hole caused by shooting into the sun. We created a Curves layer, and set it to Multiply. Then we applied a radial gradient to constrain the adjustment to the area suffering from flare, and tweaked the opacity until the adjustment blended in with the rest of the image, as shown in Figure 7-25.
Figure 7-25. Fixing the lens flare
These two adjustments don't make the image look particularly good, but they lay the groundwork for the ones that follow, "normalizing" the image so that it can better take further edits. Our next edit adds contrast by applying a layer set to Hard Light. It blows out all the detail in the sky, so we make a Color Range selection and mask the sky.
This leaves the sky pink, so we load the sky selection by Command-clicking the layer mask tile in the Layers palette, press Command-Shift-I to invert it so that the sky is selected, target the Color Fill layer's mask, and fill the selected area with black so that the Color Fill no longer applies to the sky (see Figure 7-26).
Figure 7-26. Adding contrast with Hard Light
The top half of the image is still washed out, so we add a Multiply layer, then make a gradient fill on the layer mask so that it only affects the upper portion of the imagesee Figure 7-27.
Figure 7-27. Building density with Multiply
This leaves the image quite dark, so our next edit is a simple Levels adjustmentit's a good example of the kind of edit that drove Bruce to conclude that blending modes couldn't completely replace Levels, Curves, and Hue/Saturation. We could try to do something clever with Screen blending, Curves, and a layer mask, but we've learned to recognize the dangers of our own cleverness. so instead, we opt for the simple white point and midtone Levels adjustment shown in Figure 7-28.
Figure 7-28. Brightening the image with Levels
We'd like more contrast on the foreground figures, so we add a Curves layer set to Soft Light with a medium opacity. Then we invert the layer mask to hide the effect, and paint it in where we want it using a soft-edged brush set to 50% opacity. Using a medium opacity on the layer lets us fine-tune the effect later, if we need to, by adjusting the layer opacity. If we need still finer control, we can edit the layer mask itself using Levels, adjusting the midtone slider to reveal or conceal the effect. Figure 7-29 shows the edit before and after painting on the layer mask.
Figure 7-29. Adding local contrast by painting in a Soft Light layer
The overcast sky makes the image seem too warm, so we add a Photo Filter layer using a cooling filter, then reduce the layer opacity to get the strength we want. That way, if we need to increase or decrease the strength later, we can do so by adjusting the layer opacity directly from the Layers palette, without having to open the Photo Filter dialog box (see Figure 7-30).
Figure 7-30. A cooling adjustment with Photo Filter
The image is still flat, so we add a Curves layer set to Soft Light, then reduce the opacity to 80 percent, as shown in Figure 7-31.
Figure 7-31. Adding global contrast with a Soft Light layer
This improves everything except the skin tones. Bruce would admit that alcohol had been consumed, but the braw lads are looking a wee bittie too florid, so we add a Hue/Saturation layer, and adjust the Reds and Yellows, taming the skin tones and adding a little saturation to the grass, as shown in Figure 7-32.
Figure 7-32. Hue/Saturation adjustments
We have one remaining problem: The sky is still too pink. We already have a mask for the sky, so a localized adjustment is simple, and we could do it any number of ways, including using Curves or Hue/Saturation. We opted for a low-opacity Color Fill layer set to Color blend mode, with a layer mask to constrain it to the sky. We started by loading the mask from our second Curves layer as a selection, then we inverted the selection so that the Color Fill layer would pick it up and use it as a mask, then we chose the approximate color, set the blend mode to Color, and lowered the opacity. Figure 7-33 shows the result.
Figure 7-33. A Color Fill layer
This sequence of edits may seem quite complex, but it took far less time to accomplish than it did to explain! However, it does serve to point out a major issue with making layered edits to images, whether using blend modes or simple adjustment layers.
Naming the layers
This image contains only 10 layers, not a huge number by any stretch of the imagination, but it isn't at all obvious what each layer does. We can glean a few clues by looking at the layer masks, but if we return to this image a year or two from now, we'll pretty much have to resort to turning the layers on and off to figure out what each one does.
It's a good idea to get into the habit of naming your layers informativelyjust double-click on the layer name in the Layers palette, and type in a more informative name than "Curves 78" or "Color Fill 15." Figure 7-34 shows how we'd like the Layers palette to appear when we revisit the image.
Figure 7-34. Naming the layers
Letting the Image Edit Itself
We confess to being lazy. One of the ways that laziness manifests itself is that we're always looking for simpler solutions, which in the field of digital imaging can be difficult and occasionally dangerous. But using the contrast, darken, and lighten blend modes to adjust tonality is one of those few solutions that is both simple and safe.
Bruce calls this "letting the image edit itself" because rather than having to place curve points and carefully manipulate them, the image content does all the work. If you need more contrast, apply a Soft Light or Hard Light layer. The blending mode takes the contrast that's already in the image and increases it, with no danger of clipping, and no futzing around in the Curves dialog box. Likewise, when you need to lighten or darken an image, Screen and Multiply do those things proportionally, again with no danger of clipping. Moreover, the blend modes tend to introduce less hue-shifting than major tonal moves with Curves.
Each layer affects all the layers underneath it, so we often end up going back to a previous layer to tweak it to take account of the effect of the ones above it. Using the blend modes, we can simply adjust the layer opacity without having to open dialog boxes, or when we need to make localized changes, we edit the layer masks.
Once you get accustomed to working with the blend modes, you'll find that they're useful for many different kinds of edits. But it's important to remember that the conventional tools still work too!
Mixing and matching
The following example shows how we mix blending modes with "normal" techniques. A reasonable rule of thumb is that if a blend mode edit doesn't get you where you want to be fairly quickly, and it's not a masking issuean edit that needs to be localized to a specific area in the imageit's probably time to go back to the "normal" Photoshop tools.
The image shown in Figure 7-35 is an unadjusted scan from a Kodak Portra 160 NC color negative. Two quick blend mode edits put it into a much better state for the subsequent fine-tuning.
Figure 7-35. Heavy tonal lifting with blend modes
Next, we shift the color balancethe image has a color cast that's basically cyan, as is common with scans from color negative. So we add red as a solid Color Fill layer, setting it to Color blend mode and 12-percent opacity. Then we go in and fine-tune the color (see Figure 7-36).
Figure 7-36. Fixing color balance with a Color Fill layer
The Color Fill layer generally moves the color balance in the direction we want, but it's clear that the sky is going to need a localized correction. The blue sky is relatively easy to isolate, but we need to be careful, because the dark areas on the background hills are also blue, so we'll need to take that into account when we make the selection.
We're also faced with the question of how to edit the sky color. We could use a Hue/Saturation layer, or a Curves layer, or we could apply another solid-color layer set to Color blending. They all require approximately the same amount of work, but we opt for a solid-color layer because it's likely to be the easiest of the three to fine-tune afterwards.
If we used a Hue/Saturation layer or a Curves layer, we'd almost certainly apply it at 100-percent opacity, so if we needed to make the effect stronger, we'd have to tunnel into the dialog boxes. Color Fill layers, on the other hand, always use fairly low opacities, so we have an immediately available adjustment to make them weaker or stronger using the layer opacitywe only need to open the dialog box to adjust the actual color.
So we make a marquee selection that covers the sky blue areas, then refine it with Color Range. We add a Color Fill layer with a sky-blue color. The layer automatically uses the selection as a layer mask, so we set the blend mode to Color and reduce the opacity until it looks right, as shown in Figure 7-37.
Figure 7-37. A local correction with a Color Fill layer
There is, however, the danger of falling in love with the techniques to the extent that you make extra work for yourself by overlooking the more conventional techniqueswe learned this the hard way!
We want to make the background hills less blue (the dark areas are green vegetation), and we want to increase the saturation and the separation of the red and yellow tones in the foreground. We could do this with careful masking and two or three color fill layers, but since we're dealing with separate ranges of color, and we already have a mask that isolates the blue sky from the blue hills, it makes more sense to use a "conventional" Hue/Saturation layer with the blue sky masked out.
We start by Command-clicking on the Sky color layer's layer mask in the Layers palette to load it as a selection, then we press Command-Shift-I to invert the selection, leaving everything except the blue sky selected. When we add our Hue/Saturation layer, it automatically uses this selection as its layer mask.
We boost the saturation of the foreground yellows, and shift the hue of the background hills towards green. We have to darken the green to keep the same tonality, so we reduce the lightness as well as shift the huesee Figure 7-38.
Figure 7-38. A local correction with a Hue/Saturation layer
Our next problem is that the clouds are too cyan. They're relatively easy to select, so the simplest fix is a masked Color Fill layer using red to counteract the cyan cast. (Hue/Saturation doesn't work well on colors that are close to neutral, and Curves would require quite a lot of fiddlingwe'd need to adjust at least two points on the red curve, and possibly tweak green and blue too.) Figure 7-39 shows the fix.
Figure 7-39. Warming the clouds with a Color Fill layer
Two simple blend mode edits let us adjust the final lightness and contrast. We add a Screen layer and a Soft Light layer, setting the opacities to 7 percent and 62 percent respectively. The Screen layer at 7 percent opacity provides a very gentle lightening, and the Soft Light layer at 62 percent gives a healthy contrast boostsee Figure 7-40.
Figure 7-40. Tonal fine-tuning with blend modes
One of the biggest problems in digital imaging is knowing when the image is finished! We can't claim to do better than anyone else in that department, so we have two more edits. The first is to make the foreground a little warmerwe really want it to glow. We could use a Photo Filter layer, but we find Color Fill layers easier to controlthere's one fewer dialog box to tunnel into if we need to tweak the color.
So we apply an amber warming color as a solid Color Fill layer, set the blend mode to Color, and reduce the layer opacity to 12 percent. This does wonders for the foreground but makes the clouds much too warm. So we select the Background layer, make a quick Color Range selection on the clouds, select the warming layer's layer mask, and fill the selection with black. (We had to target the background layer to make the Color Range selection because Color Range only works on layers that contain pixels, a quirk that has tripped us up more than once!) Figure 7-41 shows the image with the Color Fill layer applied, before and after masking.
Figure 7-41. Warming with a Color Fill layer
At this point, most of us would have the sense to leave well enough alonewe've come a long way since Figure 7-35but the background hills aren't quite right, so we apply the Curves shown in Figure 7-42, invert the layer mask, and paint the final correction in with a soft-edged brush.
Figure 7-42. A masked Curves correction