For example, let’s take a look at this image of Palos Verdes, on the California coast.

The vista is beautiful, but a little more contrast would help to make this photo more dramatic. The standard way to introduce added contrast within Photoshop is by applying a tone curve, and the best way to do that is with an adjustment layer. In this case, adding a Curves adjustment layer and laying in a steep “S” curve, we get not only added contrast, but the saturation goes off the scale. We no have neon water and orange hillsides, and the sky is just too unbelievable:

So what do we do? Layer blending modes come to our rescue, of course. Simply change the adjustment layer’s blend mode from”Normal” to “Luminosity,” and the psychedelic colors are gone – the saturation is returned to normal, but we still have our contrast in the image. Nice!

The same principle can apply beyond simple adjustment layers. We can use it anywhere a creative move causes color shifts, including the technique of scaling back some of the wild effects of some of today’s popular plug in filters. In this next example, we’ll look at using this principle with the popular Topaz Adjust. I’ve started with this grand but somewhat plain photo of Edinburgh castle:

Wanting to add a little pizazz, we make a copy of the background layer – this is the key – and run Topaz Adjust, picking the “spicify” setting. This is one of my favorites, but sometimes it can be over the top. As we see here, the effect has introduced some nice detail, but the colors are now quite unbelievable. This is typical of a lot of images I’ve been seeing out there today, easily recognizable:

Now, here’s what we do. As before, change the Topaz layer’s blend mode to “Luminosity,” and watch the improvement. Adding it on a layer allows us to adjust the opacity as well, for a very fine level of control over the effect; in this case I opted for an opacity of 87%. Much nicer than the straight-out-of-the-box Topaz effect, and much less likely to distract the viewer:

I’m a fan of subtle effects and gentle application of creative techniques, and adding these effects on a layer always gives you more control. And now, you know that Luminosity blending can help further by eliminating unwanted hue and saturation shifts in your creative work flow. Try it for yourself, and enjoy the results!

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Today, we’ll apply this technique to our sharpening workflow. If you’ll recall in the last lesson, I showed an example of an image that was sharpened heavily, and the resulting halo along the edge boundary had developed some weird color shifts as a result of the sharpening:

Let’s take a look at three ways to use the principles we’ve seen with Luminosity Mode blending to eliminate the color shifting, and leave the hue intact as we add brightness and darkness along the edges to sharpen our images. You may have seen recommendations that you convert your image from RGB to Lab and sharpen the L channel, then convert back to RGB. This technique will achieve essentially the same result, without the conversion – and without having to flatten a multi-layer image.

1. Using Fade

Let’s start with this next image of some sweaters on a rack, and we’ll simply begin with our trusty friend, Unsharp Mask. We apply an aggressive low radius, very high amount for our sharpening in a single step, to a single layer (probably the most inflexible approach):

Click OK, and the IMMEDIATELY choose Edit > Fade Unsharp Mask (you must do this as the next step, a single click will cause this command to be grayed out). In the Fade dialog, we see an opacity slider that we can use to lessen the effect, but what else do we see? That’s right, blend modes! Let’s reduce the opacity to about 67%, and change the blend mode to Luminosity:

Click OK, and mission accomplished. If we take a very close look at the knitted yarn on the sweaters, we can see the effects of before, after sharpening, and after fading to luminosity. Notice the garish colors in the original sharpened image, which have been toned down considerably after fading to luminosity blend mode:

2. Using Layers

As I mentioned above, applying the Unsharp Mask (or any sharpening technique) to a single layer is the most inflexible way to approach your workflow. If you make a mistake, you have to undo and try again, and while “Fade” allows some flexibility, you only get one shot. Let’s try something a bit more flexible. A separate sharpening layer.

If you have only a single layer in your file, simply drag the layer to the “Create New Layer” icon to make a copy of the background layer. If you have multiple layers, select the layer at the top of the stack, and press “Ctrl-Alt-Shift-E” (on a Mac, that is “Cmd-Opt-Shift-E”). This is the “Stamp Visible” command, and it creates a composite image of everything that is visible, all on a single layer, above the one previously selected. Perfect for sharpening!

Our image is ready:

Now, we run Unsharp Mask as before, this time on the top merged or copied layer:

As before, we go in aggressively, intentionally oversharpening so we can back off to a more appropriate setting. Since we’ve sharpened this individual layer, let’s set the blend mode of the layer to Luminosity, and the Opacity of the layer to 67%:

Now we’ve achieved the same results as with Fade… except for one key advantage: We can modify the opacity of this layer at any time in the future, even after saving and coming back again later. This allows us a much better control over the effect. In addition, since this is a separate layer, we can add a layer mask and hide any areas where we don’t want sharpening to occur. Much more flexible than the straight sharpening on the original layer.

3. Smart Filters

For the ultimate in control, however, we must turn to a great new feature introduced in Photoshop CS4, and this one has been a long time coming: Smart Filters. This feature will allow you to control not only the intensity of the effect, but you can actually go back and re-adjust the settings of the Unsharp Mask (or any other filter used in this way).

Smart Filters make use of Smart Objects in Photoshop, and require us to have a separate layer as in the previous example. Here, I’ve used “Stamp Visible” to create a composite layer at the top of the stack:

Now, we want to convert this new layer so that we can use Smart Filters. We can use the menu command Filter > Convert For Smart Filters… then click OK at the warning dialog box:

Now, notice that the layer has been converted into a Smart Object. This is indicated by a small icon in the lower right part of the image thumbnail in the Layers panel:

Now that we have a Smart Object, any filter we apply will automatically be a Smart Filter. Let’s use our trusty Unsharp Mask just as before:

When you click OK this time, look at the layers panel and notice the difference. The Unsharp Mask is added below the layer, with an eyeball icon for visibility (similar to layer effects) and even a Smart Filters mask that you can use to specifically control the areas where the Smart Filter is visible.

However, I want you to notice specifically the little icon to the right of “Unsharp Mask,” that looks like a couple of sliders. Double click this icon, and you get the Blending Options dialog for the Unsharp Mask filter itself!

Once again, we can set the blend mode to Luminosity, and adjust the opacity of the Unsharp Mask filter independently of the layer settings.

Now, here’s the bonus: double click the words “Unsharp Mask” and you get the original dialog box, so you can tweak the sharpening settings – as often as you’d like, until you find the right setting!

Surely, this third method offers the greatest flexibility of all – in that every parameter remains adjustable in your file forever. You’ll never paint yourself into a corner again!

There you have it: three ways to use the Luminosity blend mode in a sharpening workflow, and still more hidden nooks and crannies of Photoshop where we can encounter the power of Blend Modes to give us a greater flexibility and creativity with our images.

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For example, take a look at this document, which has some noticeable color shifts along the edges, as a result of sharpening. We can use Luminosity blend mode to prevent this type of result:

 Before we start with the sharpening workflow, we’ll need a basic understanding of the Luminosity blend mode. Luminosity is one of the four tonal blend modes located near the bottom of the blend mode list. In its simplest terms, when you combine a layer in Luminosity blend mode with another layer, the resulting color keeps the original layer’s hue and saturation, but the luminosity value ONLY comes from the new blending layer. Let’s demonstrate with a quick example.

 We’ll start with a one-layer document, and add a gradient as shown below. The gradient transitions from a red value (RGB: 128, 0, 0) to a blue value (RGB: 0, 0, 128).

 If we examine the foreground and background colors with the color picker, notice the HSB values located directly above the RGB values. In both cases, these colors have a “B” (Brightness) value of 50%. This indicates that while the “H” (Hue) and “S” (Saturation) values change across the range of the gradient, the Brightness, or Luminosity, of the colors is constant – 50% throughout the image.

 Before proceeding, we want to change our foreground colors again – change the foreground to an RGB value of (180, 255, 82). Notice that the luminosity of this color, as evidenced by the “B” Brightness value, is 100%:

 Again before proceeding, let’s change the background color to an RGB value of (54, 77, 24). Notice that the luminosity of this color (the “B” Brightness value) is 30%. Also notice that the Hue and Saturation values are identical to the foreground color:

 Now add a new layer to the document, and fill it with the foreground color by pressing Alt-Backspace (Option-Delete on a Mac). With this layer still selected, we select the command Filter > Render > Fibers and accept the default values in the dialog box by clicking OK. We have this result:

The fibers are rendered in colors ranging from the foreground to the background colors, which differ ONLY in their Brightness, or luminosity value. Let’s bring blend modes into play. With the fibers layer selected, change the layer blend mode to “Luminosity:”

We can see that, although the layer with the fibers has a range of garish green colors, the Hue and Saturation of the greens are completely ignored, but the Luminosity, or Brightness, remains. The Hue and Saturation of the original bottom layer shows through, but its Brightness values are over-ridden with the Brightness of the fibers layer.

The key point to take away from this – it doesn’t matter at all what Hue or Saturation the fiber layer is – ONLY the Luminosity is retained when using this mode.

We’ll use this principle to great advantage next week as part of a sharpening workflow. Stick around!

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