Introducing the Luminosity Blend Mode

Whether you produce your images for web or for print, at some point you’ll want to sharpen the images for output. Sharpening, as we’ve discussed in earlier tips, is a process in which the edges of detail are enhanced by making the dark side of the edge slightly darker, and the bright side slightly brighter – in effect, increasing contrast along the edge. However, in many cases, sharpening can introduce unwanted hue shifts as a result of the way the darkening and lightening affects the image. We can use Photoshop’s Luminosity blend mode to remove the color artifacts, leaving us with a cleaner result.

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!

Creative Differences

Last week we looked at some practical and very utilitarian ways to take advantage of Difference blend modes in Adobe Photoshop. Today, we’re going to take a 180 degree turn and look at some ways of using the Difference blend mode in some creative and artistic techniques. So let’s get in to the artistic frame of mind and take the creative plunge.

Difference mode can be a very interesting way of working with multiple images in a collage. Since Difference mode, you may recall, magnifies and highlights the differences between images, this technique work especially well with images that have nicely saturated colors and good contrast. We’ll start with this image as our base:

Now, we’ll open our second image, and drag it directly onto the first, so we have both layers in a stack, like so:

Now, simply change the blend mode to Difference, and look what happens:

Now, if you’re on Windows, when you have the blend mode highlighted in the layers panel, you can press the up or down arrows to cycle through the blend modes – this is really useful in cases like this as you experiment to see what looks cool. Mac users can do this by pressing Cmd-plus and Cmd-minus to move through the blend modes. Either way, experiment and see what happens. Most often, I find Difference blend mode to be one of the more interesting results.

Now let’s look at another technique. I saw something like this in Photoshop User magazine many years ago, and it is a really cool technique for making futuristic abstract backgrounds and textures. Lets start with a new document, white canvas, at the default Photoshop size.

Now, let’s select a nice saturated green color as our foreground color. Then, choose the gradient tool, and from the gradient picker, choose foreground to transparent and select linear as the style.

Now, look in the toolbar just to the right, and what do you see? Yes, yet another of the hidden spots within Photoshop where blend modes are available. Let’s set the gradient tool’s blend mode to Difference, and draw a random gradient (again, make sure you have foreground to transparent set in te gradient picker:

Nothing special, right? Now let’s drag out another gradient, and watch the colors interact with the difference mode:

Cool! Now drag out some more in succession, like so:

And a few more in random directions:

Now, let’s switch to a saturated blue and drag a few more times:

Now, a saturated red and continue:

Now, some yellow… and for variety, lets switch to the radial gradient:

A few more times:

You get the idea – you can keep playing with this all day, creating new wild gradient blends with Difference mode. Here I’ve added some type and set the type layer blend mode to Difference as well:

Experiment, get creative and have fun!

Image alignment and analysis with Difference Blending

Way back when we started our journey through the dark and forbidding lands of Photoshop Blend Modes, I showed this chart, grouping the blend modes into some distinct categories:

If you look closely, you’ll notice that there are a couple in the middle that don’t fit into the other categories, and today we’ll take a look at one of them: the Difference blending mode. As the name implies, this mode is useful for finding the “difference” between two layers, but it also has some creative uses as well. In this tip, we will focus on the more utilitarian purpose, and see how Difference mode can help us to align and analyze images.

First, a bit of an overview of what difference mode does. It compares the colors of the current layer to those below, and subtracts the two to arrive at a resulting color. This has three special secret effects:

1. Blending with pure white as the color will completely invert the image. This provides the same result as using the Image > Adjustments > Invert command.
2. Blending with pure black as the color has no effect at all. Recall that black pixels have a tonal value of 0, so subtracting 0 makes no change.
3. Blending two identical colors together will result in pure black. Since the values are the same, when subtracted, the result is 0, which is the value of black.

 

We can see this in action below. We’ll start with this image:

Now, let’s add a new layer, with a simple black to white gradient. Change the layer’s blend mode to “Difference” and you can see that the white part of the gradient has inverted the image, while the black part has left the image unaffected:

This demonstrates special effects 1 and 2 from above. Now let’s look at special effect #3.

First, we delete the gradient layer. Then, duplicate the background layer and set the duplicate to “Difference” blend mode:

Notice that, although you can clearly see the images are the same in the layers panel, the net result of subtracting the two (Difference mode) is that the entire image turns black. The main point to realize is that this happens because EVERY pixel is the SAME.

What if we take the move tool, and nudge the top layer to the right a few pixels? You can do this my selecting the Move tool (V) and using the arrow keys to nudge one pixel at a time. Notice that even with a move of one pixel, there is a noticeable change. Take a look:

You might start to see where I’m going with this: you can use this feature to line up layers, one on top of another, by nudging them into position. Modern versions of Photoshop (with Photomerge) have some pretty sophisticated stitching capability, so this isn’t always as useful as it once was. But it can still get you out of a bind, and it works on any document regardless of how many layers you have.

For example, I worked on a project recently in which I was scanning in an entire front page of a newspaper – a 30-year-old newspaper, brown and aged, with creases, dust, you name it. Now, my scanner isn’t the size of a full newspaper, so I had to do it in segments. And, with the sad condition of the paper itself, Photoshop’s Photomerge feature wasn’t cooperating – so, I had to stitch by hand.

Here’s a view of a couple of layers I was trying to align:

You might be tempted to lower the opacity, but that’s really hard to see. Let’s change the upper layer to Difference mode (temporarily):

Notice how in the overlapping area, you can see both layers, and you can see that they are not aligned. Grab that move tool, and get a rough alignment by dragging the top layer:

Notice how the closer you get to alignment, the more areas turn black? No, it’s time to switch to the arrow tool and start nudging one pixel at a time:

You’ll know you have the best possible alignment when a one-pixel nudge in any direction results in more color appearing. You’ve reached the center of alignment (don’t forget that some images might require rotation or resizing to get the alignment perfect). Once your image is in alignment, simply change the blend mode back to “Normal.”

One last tip for today: you can use this not only for alignment, but for analysis. Recall our image from a few weeks ago when we looked at softening with Overlay:

What if we wanted to do a quick check to see where we made our modifications and retouches on this image? We simply duplicate the original, bring it to the top of the stack, and set the blend mode to “Difference:”

 

Now the differences are visible, but at this resolution, and without a good monitor, it is really hard to see! Can we do something about it? Of course!

Let’s add a new layer to the top. Fill it with white, then set the blend mode of the new layer to “Color Dodge.” BOOM! The lighter areas are amplified and it is easy to see where we made our retouches from the original image:

I hope you found today’s tip useful! Stick around for next week, when we will explore some of the more artistic ways of using Difference blending mode.

Making a Vingette With Photoshop

Don’t forget we’re still after your “Photoshop @ 20” paragraph for Thursday’s post: More details

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Making Stars with Photoshop

 

A quick look at how to make stars (and a triskaidecagon) in Photoshop.

 

  

 

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Top Tip Tuesday – Creative Masks with Photoshop

Top Tip Tuesday – Blend If

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Top Tip Tuesday – Graffiti

 

 

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Top Tip Tuesday – Making a Rainbow (and rain)

 

  

3D Glass Ball using Layer Styles

By: Rebecca Fryer

In this tutorial it’s my aim to take you through the process of creating a convincing 3D Glass Ball using basic layer styles and gradients.

Step One: Basic Shape & Fill

Firstly I created a new document (as above) and filled the background with a Radial Gradient using the Gradient Tool (G) set to the preset of Foreground to Background with White as your Foreground.

I clicked and dragged to simulate light coming from the top left corner.

I then added a Hue & Saturation Adjustment layer set to Colorize to give the background gradient some colour.

Click to Enlarge

You might be wondering why I chose to do it that way and not pick the colours for the Gradient Fill to begin with. The reason is flexibility, to be able to change hue, saturation and lightness to refine the end image.

Next I created an Ellipse Shape Layer (U) filled with #00c0ff colour (The colour is your choice depending on the final look) and set to an Overlay Blending Mode.

Pressing [Ctrl]+ LMB on the Vector mask thumbnail in the Layer Palette will load the shape as a selection, create a new layer above and using the Gradient Tool set to a Radial Gradient fill with White-to-Black starting from the point where you want the highlight to be on the sphere then drag in the opposite direction of the light. This will create a 3D effect to the selection – deselect this selection [Ctrl]+[D] and set the gradient filled layer to a Multiply blending mode and it inherits the colour from the Vector Layer.

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Okay so it looks less flat but hardly convincing 3D!

Step Two: Specularity & Shadow

First we need to put the Vector and the Gradient layers into their own group and name this group appropriately.

So we need to add a specular highlight to create a hotspot of light, so using the Elliptical Marquee Tool [Shift] drag an Ellipse selection where the light would strike the ball and fill with White. Deselect the selection and add Gaussian Blur to suit your image – Less for the impression of more reflectivity and more blur to give it a more Plastic look.

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You can lower the Opacity if you feel the highlight is too strong. You can even do a more custom shape to look like a studio light with a soft box or maybe like light from a window.

I also duplicated the specular layer and moved it below and to the right of the main highlight using the Move Tool (V) and set this layer to a Soft Light Blending Mode this was my preference but I leave the finer details down to your own taste.

Next duplicate the Gradient layer and place it above the highlight layers – this layer we will apply filters to create some inner glow and stroke using the following settings.

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As you can see on the Stroke FX I used an Inside stroke set to Soft Light with a Gradient Fill Type this was to give the appearance that the globe was hollow and therefore you could see thickness of the glass, once again this was my preference you could opt to leave this out and treat the globe as solid glass or crystal. The Inner Glow gives a nice sense of glass and depth to the Globe. Be sure to use a glow colour similar to the colour of your background but a few shades lighter.

Now that the first group is complete duplicate this group and rename it – something like ‘Multiply Group’.

Change the Blending Mode on the Vector Shape layer within this group to (of course) Multiply.

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Already it’s taking on the shape of a realistic glass globe but the purpose of this second group is to apply extra depth using Layers Effects to the FX Layer of this group. So we have to delete the Stroke and replace with an Inner Shadow.

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Also to boost the Inner Glow FX its Opacity was raised to 35 within this layer. Return to the first group and change the Blending Mode of the FX Layer from Multiply to Lighten to make the globe really pop.

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Step Three: Shadow & Falloff

At the moment the globe appears to be floating in space so let’s set a shadow and some reflection to really put the globe into the scene.

To start with grab a selection from the Vector Layer ( [Ctrl]+LMB on the Vector layer Mask in the Layer Palette) and create a new layer below the two grouped layers and fill the selection with Black (or if you want to sample a dark green colour from the background that would be better) and set this shadow layer to Multiply.

Next we need to do so finger-dancing with the Transform Tool – this is good practice – but just before we start on that create a layer mask and using a Linear Gradient White-to-Black drag a gradient onto the Layer Mask.

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This creates a fall-off effect – which is easier to do now than after the transformation. Now [Ctrl]+LMB click on the layer mask to load it as a selection, [Ctrl]+[Shift]+I to invert the selection now click on the Shadow layer’s Thumbnail icon in the Layer Palette to select that layer and add a Gaussian Blur.

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This applies a fall-off blur. Deselect the Selection [Ctrl]+D and we are ready to Transform the shadow.

[Ctrl]+T to bring up the Transform Tool transform box then press [Shift] and grab the top middle handle and drag down until the shadow sits correctly in the background and release the mouse button but don’t press [Enter] yet.

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Next press [Ctrl]+[Alt]+[Shift] and grab one of the top corner handles and drag outwards to simulate that a shadow will grow the further away from the object. Release the mouse button but don’t press [Enter] just yet one more stage to go.

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So far so good, we will now transform the Shadow to fall in the opposite direction of the light. [Ctrl]+[Shift] grab the Top Middle handle again and drag to the left like so.

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Press [Enter] to commit the Transformation.

The Shadow at the moment makes the object look as if it has no real depth so using Move Tool (V) and the arrow keys nudge the shadow down a little.

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Add a Gaussian Blur of about 5 pixels will soften the overall shadow.

Next as we have done before create a new layer and grab a selection from one of the Vector layers and fill with a dark colour sampled from the background. Transform this filled shape down grabbing the top middle handle and pressing [Shift] like we did before and press [Shift]+[Alt] whilst dragging one of the top corner handles to scale it down before releasing the Transform box nudge it into position and then hit [Enter] this will be a more solid shadow which gives weight to the globe.

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Add a Gaussian Blur of about 5 pixels again and now the Globe sit perfectly into the scene. Play around with the positioning to your own tastes.

Step Four: Reflection

Finally in this stage we will add a reflection – now this is tricky but if you follow closely you’ll be able to do perfect reflections without having to flatten the whole scene.

First hide all the layers (click on the eye icon in the Layer Palette) except the two globe groups, create a new layer above these groups and press [Ctrl]+[Alt]+[Shift]+E which will merge all the visible layers into one layer as a copy this will be your reflection layer name it appropriately.

Switch the visibility of the other layers back on now and Transform Flip Vertical this layer and move the layer to below the shadow layers. Nudge it down until it sits in the right place for a reflection.

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Change the Blending Mode to Soft Light and add a layer mask and apply a Linear Gradient (White-to-Black) to this layer mask to create a fall-off effects as with the shadow layer.

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As with the Shadow Layer [Ctrl]+LMB click on the Layer Mask to load as a selection [Ctrl]+[Shift]+I to invert the selection and click to select the Reflection Layer’s thumbnail and apply a Gaussian Blur of about 15 pixels for the fall off blur then deselect the selection and apply another Gaussian Blur of about 2 pixel to give an overall blur.

Okay everything looks lovely but unfortunately the globe isn’t as transparent as it should be so we will fix this by going to the Multiply Group and [Alt] clicking between the layers to clip them to the Vector Layer.

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So that’s the effect you could add some finishing touches by grabbing a selection of the globe as before and applying a Filter>Distort>Spherize… to both shadow layers and the reflection layer to give a truer distortion through the glass and applying a Vignette to a merged copy of the layers using Filter>Distort>Lens Correction…

I hope you’ve enjoyed this lengthy tutorial – have fun.