Modular Photo-Art 01: Edge Sketches

[Andrew B.]

Modular Photo-Art 01: Edge Sketches

What is Modular Photo-Art?
Modular Photo-Art is an attempt to create a series of threads with each thread focusing on one technique and its variations. It is intended to provide building blocks and modifications that can lead to the creation of photo-art. These are not comprehensive tutorials that lead to a specific result; they are methods and techniques that can be used along the way to alter the path of a picture or solve problems.

Ideally, the threads will be built through the contributions of members, and they will provide a focused and comprehensive resource for solving a particular type of problem, or making a specific type of move in the creation of photo-art.

In this first thread I am beginning with several messages to give an idea of the types of things that can be added to a thread. I am not the moderator or the primary author of these threads; I will only be taking the lead on the first few to help get things started.

To find out more and/or discuss Modular Photo-Art, check out the introductory thread here.

What are Edge Sketches?
The terms “sketch” and “edge” are often used interchangeably when working with photo-art, but not all sketch methods use edges. Edge sketches are usually photo-rendering methods that find edges and draw lines along the edges, usually eliminating the rest of the photo. Depending on the image and method, the lines can be simple and clear or complex, noisy, and varied. Edge sketches can be used as stand-alone photo-art to simulate pencil or charcoal drawings, but more often they are used to create a “drawn” look in combination with other techniques.

Here is an example of a picture I made that relies heavily on edge sketches: here

Note: Most of the methods I will be posting were not invented by me. And the one or two I did think of were probably in use for years before I thought of them. They are also known to many people here in RetouchPRO, but I wanted to lead with them because I think they belong in any comprehensive resource that deals with edge sketches.

[Andrew B.]

Basic Invert Blur Sketch
I don’t know who invented this, but many people find this to be a handy method for creating edge sketches. And until someone comes up with a better name, I’m going to call this method “Basic Invert Blur Sketch.”

Making a “Basic Invert Blur Sketch.”
1. Duplicate your background layer onto a layer above it.

2. Desaturate the new layer (this turns it into a black and white image)

3. Duplicate the desaturated layer onto a new layer above it.

4. Invert the top layer (this turns it into a negative image)

5. Set the blending mode of the new layer to Color Dodge. This should turn your picture completely white. But it might not. There might be black spots or even blotches. For now, we will just continue with the steps and deal with these blotches later, if necessary.

6. Gaussian Blur. This is the step where your edge sketch appears. The level of Gaussian Blur is usually in the range of 1.5 to 4.5. You will have to see what looks best to you. But often, what seems to be just a tad too light, works best if you are combining this with other techniques. So experiment with this a little. And when you see other people do pictures you like, ask them for advice on the settings.

7. Merge the top two layers. The appearance won’t change, but this will combine the two layers that are creating the edge sketch into a single layer.

That’s all there is to it. Unless spots or blotches show up in Step 5, and they are causing trouble. Usually the blotches won’t be a problem because they fit into the sketch nicely. But sometimes they mar the effect. So after you merge the layers you can touch up by hand. Or what I sometimes do is go back to Step 5 and set the blending mode to Linear Dodge. So far this has eliminated the blotches every time. But it also gives a slightly softer edge. So see if it works for you. And, you might even like Linear Dodge better than Color Dodge even if you don’t have blotches. So this could be used as a variation of the “Basic Invert Blur Sketch.”

Attached is an image that shows before and after versions of this method. In this case, Gaussian Blur was set to 2.5. If the image looks too light to you, just remember that this is only part of the process of creating an image.

[Andrew B.]

Intensify
Let’s say you created your edge sketch and moved onto other steps. But you don’t seem to be getting the results you want. One thing you can try is to go back to your edge sketch and intensify the lines.

Darken
1. Copy your flattened sketch layer to a new layer above it.

2. Set the new layer’s blending mode to Multiply (the lines will become darker).

3. If you want it even darker, make additional copies of the “multiply” layer on top of the stack until the lines become dark enough.

Thicken
1. Make sure your flattened edge sketch layer is active.

2. Select all

3. Copy

4. Go to the Channels Palette and add a new alpha channel. Then click on it to make it active.

5. Paste

6. Click the RGB layer in Channels so all channels are active again.

7. Go back to the Layer Palette.

8. Load the new channel as a selection

9. Invert the selection.

10. Set your foreground color to black (you can vary this as needed).

11. Stroke the selection with a pixel setting of 3 to 5 (the lines become thicker)

12. Dial in the correct pixel setting by using undo and redo at different stroke settings until it suits you.

Attached is an image that shows the results of these two methods. I applied these to the edge sketch from my previous message, but you can use these on a variety of edge sketches.

[Andrew B.]

Refine
You have created your edge sketch but as you work further into your image the noise or clutter in the lines is ruining the image and you want to step back and try out some smoother lines.

There are two filters I know of that have the ability to take edge sketches and refine the lines, giving them a more-even quality, along with adding their own unique style to the lines. I’m still looking for other filters that can do this, so suggestions are welcome.

Diffuse|Anisotropic
I think of this filter as something that melts lines a little and makes them a bit more curvy. There are no settings in this filter, but you can adjust the intensity by fading or using more than one application.

Cutout
This filter can gather many small lines that are close together and join them into broader and simpler lines.

In the attached image, I applied Diffuse|Anistropic to my previous “darken” example, and Cutout to my previous “thicken” example. The results will be different depending on the edge sketch you apply them to.

[Andrew B.]

Color
You decide that you want some of the color from the original image to interact with your edge sketch.

1. Make sure your edge sketch layer consists of a single layer sitting over your original picture.

2. Dial through the blending modes on your edge sketch layer until you find one you like. I usually find that Overlay or Luminosity work the best.

3. Adjust the opacity of the edge sketch layer as needed.

The attached image shows the effects of blending with Overlay and Luminosity. Overlay is applied to the “anisotropic” image from my previous message, while Luminosity is applied to the “cutout” version.

[Andrew B.]

Combine
There are times when I keep trying different things, each one has some nice qualities, but nothing is exactly what I want. For example, in my previous message there is one version that is intense and somewhat photographic, and another version that is very soft. Each has some qualities I like, but neither is quite right. So I try combining them to see if I get the best of both worlds. In the attached image I placed softer one above the harsher one and set its opacity to 64.

And, of course, this is not just a method for edge sketches. But it is a single step that can sometimes overcome a problem in developing a picture from an edge sketch.

[Andrew B.]

What's next?
The last image in my series of messages is not the final image, imo, and any of them could be used to branch into things like brush strokes, filter techniques, etc. Also, none of what I did was earthshaking or arcane. The point of these threads is to provide one-stop shopping for intermediate photo-artists who are trying to solve problems or learn several ways to move their photos from one place to another. So please add your own techniques, or methods you have learned from others -- or just post links that apply to this thread in Modular Photo-Art. And if you want to offer feedback or suggestions for Modular Photo-Art, please visit the main discussion thread here

[tyeise]

Sometimes as a variation for the Basic Inverse Blur that you mention, is to not desaturate it. If you leave it colored, and try different methods for blurring it (Blur, unsharp mask, soften, etc.) you can get some nice colored outlines. You can always desaturate these later if you want.


Tyeise

[Andrew B.]

Tyeise said:

>If you leave it colored, and try different methods for blurring it (Blur, unsharp mask, soften, etc.) you can get some nice colored outlines. You can always desaturate these later if you want.<

I don't think I ever tried that. But I just did and it yielded some nice results. I also tried some noise reduction filters and they worked well too.

Thanks for the tip.

[Andrew B.]

Here is a variation that shows some promise. This can be used with the desaturated method I posted or the color method Tyeise added. And it's pretty simple.

After you do your Gaussian Blur, turn down the opacity of the top layer. To get an idea, start at about 80%, then raise and lower to see how it changes. It gives a whole different feel. Sort of a fuller feel. Might even save some steps, depending on where you are going.

[tyeise]

Hey, that's neat, Andrew. Thanks.

Tyeise