Photoshop Brush Tutorial: Shape Dynamics - Size Controls

See Also: Shape Dynamics - Angle Controls  |  Shape Dynamics - Roundness Controls

The first Photoshop brush control in the list is "Shape Dynamics", which gives us various ways to control the brush's size, angle, and roundness, and even gives us the ability to randomize them by using "jitter" controls.

To access the Shape Dynamics control panel from the Brushes palette, first make sure you have the Brushes palette open on your screen (press the "F5" key on the keyboard to quickly open and close the Brushes palette). You'll also need to make sure you have the Brush tool selected in the Tools palette, otherwise all of the options in the Brushes palette will be grayed out and unavailable.

With the Brush tool selected and the Brushes palette open, I'm going to pick a brush to use. I'll click on the words "Brush Presets" at the top of the Brushes palette to access a list of the available preset brushes, and then to keep things simple, I'll choose one of Photoshop's standard round brushes from the list on the right. The 19 pixel round brush will work just fine, as shown below:

Now that I have my brush selected, I'm going to click directly on the words "Shape Dynamics" in the left hand column of the Brushes palette:

Make sure you click directly on the words "Shape Dynamics" and don't simply click inside the checkbox to the left of the words. Clicking in the checkbox will enable the various shape dynamics to affect your brush as you paint, but won't give you access to the control panel for these controls. You need to click directly on the names of the various controls (Shape Dynamics, Scattering, Texture, etc) to access their respective control panels.

After clicking on the words "Shape Dynamics", the Brushes palette changes from giving me a list of available brushes to the Shape Dynamics control panel:

As I mentioned above, there's three different aspects of the brush that we can control in Shape Dynamics - Size, Angle and Roundness. Let's start with size:

Shape Dynamics: SIZE

The first section in the Shape Dynamics control panel gives us various options for controlling the size of our brush. Now, before we continue, you may already be asking yourself, "Didn't he already choose a size for the brush when he selected the 19 pixel brush for these examples? Isn't '19 pixels' the size of the brush? Why are we looking at even more ways to change the size of it?" Well, you're absolutely correct, I did pick a 19 pixel brush for these examples, and if I wanted to change the size of it, I could go back to the Brush Presets and either choose a different size brush or use the Master Diameter slider to change the size of this current brush. But that's not what we're talking about here. These are shape "dynamics". They don't simply set the brush to a certain size and then leave it there. These controls can actually change the size of the brush dynamically while we're painting! We're not picking a size for our brush here. You're right, we've already done that. What we're doing here is telling Photoshop that we want it to keep on changing the size of our brush as we paint with it, which opens up a whole new world of creative possibilties.

Here's a screenshot of the various controls we have for dynamically changing the size of our brush:

As you can see, we have a "Size Jitter" control, a "Control" option, a "Minimum Diameter" control, and a control which is grayed out at the bottom, "Tilt Scale". Let's look at each one separately, starting with "Size Jitter".

Changing the Photoshop Brush Size Randomly with 'Size Jitter'

First of all, what does "jitter" mean? Well, "jitter" simply means randomness, so when you see "size jitter", "angle jitter", "roundness jitter", etc., replace the word "jitter" in your mind with "randomness". This first control then, "Size Jitter", controls the randomness of the size of the brush as you paint.

Normally, when you select a brush and a size for the brush, the brush remains at exactly that size the entire time you're painting with it, at least until you change the size again. Size Jitter causes the brush size to change randomly as you paint. You can control the randomness of the brush size by setting a percentage of the brush's maximum size (the size you currently have selected for the brush) as the smallest size the brush can be. Photoshop will then change the size of the brush continuously as you paint based on sizes randomly chosen between its current maximum size and the percentage of that maximum size you entered.

In my example here, I've selected a 19 pixel brush, which means my brush has a maximum size of 19 pixels. It won't go any larger than 19 pixels while I'm painting, unless I change the size again myself to something larger. Photoshop can't randomly make the brush larger, but it can randomly make it smaller, depending on how small I tell Photoshop it's allowed to make it, and I tell this to Photoshop by entering a percentage value in the Size Jitter input box, which by default shows a value of 0% as you can see below:

If I was to enter 50%, for example, I'd be telling Photoshop that it can randomly pick any size for my brush between the brush's maximum size (19 pixels in this case) and 50% smaller than its maximum size. If I entered 25%, it could randomly make the brush any size between 19 pixels and 25% smaller than 19 pixels.

To enter a value for the amount of size jitter, you can either type a value directly into the while input box on the right hand side, or you can drag the slider bar to increase and decrease the value as you drag. Using the slider is the best way to enter a value because the Brushes palette gives you a live preview at the bottom of the palette showing how the value is affecting your brush as you drag.

Here's what the preview looks like with my Size Jitter set to a value of 0% (the default value), which means size jitter is currently having no effect on my brush at all. Notice how the brush remains the exact same size throughout the entire length of the stroke:

If I increase the amount of size jitter to 25%, as shown below:

I can begin to see the effect that Size Jitter is having on my brush in the preview at the bottom of the Brushes palette :

The stroke, which was smooth a minute ago, is now starting to look a little "lumpy" because the size of the brush is being dynamically changed by Photoshop throughout the length of the stroke. If I increase the amount of size jitter further, to 50%:

I can see my brush becoming even lumpier in the preview, as the size of the brush is now being randomized using any size between its maximum size and exactly half of its maximum size:

And if I drag the slider all the way to the right, setting my size jitter value to a full 100%:

I can see the full effect that size jitter can have on my brush, as Photoshop is now free to make my brush any size it wants, as long as it doesn't go above the brush's maximum size of 19 pixels :

We can see in the previews above that as I increased the Size Jitter value, the size of the brush became more random throughout the length of the stroke, and at a full 100% for Size Jitter, we ended up with a very "lumpy" effect. Unfortunately, "lumpy" doesn't really do a very good job of explaining what's really going on here, so to see things more clearly, I'm going to back out of the Shape Dynamics control panel for a moment by clicking on the words "Brush Tip Shape", directly above Shape Dynamics in the left column of the Brushes palette. This will take me to the general options for the brush tips, as shown below:

The option I want to change here is "Spacing" down at the bottom, directly above the preview box, which by default is set to 25%. What is "spacing"? Well, when you're painting with a brush in Photoshop, it may appear to you as if Photoshop is laying down a continuous stroke of paint, but what it's really doing is stamping the canvas with the shape of the brush as you drag the brush along. When the "stamps" are close enough together, they create the illusion of being one continuous stroke, but they're really just a series of stamps of the brush's shape and size. Photoshop sets the distance between these brush stamps using the value that's currently entered in the "Spacing" option under "Brush Tip Shape". The default value is 25%, which means that every time you move the brush a distance equal to 25% of the size of the brush, it will lay down another stamp. This is why, in our previews of Size Jitter above, our brush appeared "lumpy". Each "lump" was Photoshop laying down another stamp of the brush, and it stamped the brush every time I moved the brush a distance equal to 25% of my brush's current maximum size, which was 19 pixels.

If I change the Spacing value to 100%, which I'm going to do in a moment, this will tell Photoshop to stamp the brush shape onto the canvas every time I move the brush a distance equal to 100% of my brush's current maximum size. The first thing I want to do though is temporarily turn off the Shape Dynamics controls by clicking inside the checkbox to the left of the words "Shape Dynamics", which will uncheck it. Having done that, I'm going to drag the slider bar under the word "Spacing" to the left until the value showing in the white input box is 100%, as shown below:

Once again, Photoshop gives us a preview of how what we're doing is affecting our brush in the preview at the bottom of the Brushes palette. Now that I've changed the "Spacing" value to 100%, Photoshop will wait until I've dragged the brush a distance equal to the full maximum size of my brush before it lays down a new stamp of the brush, giving me a "string of pearls" type of effect for the stroke, as shown in the preview above.

Now we'll be able to see much more clearly how Size Jitter affects our brush. I'm going to go back to my Shape Dynamics control panel by clicking directly on the words "Shape Dynamics" in the left column of the Brushes palette as I did previously, which will not only take me back to the Shape Dynamics control panel, it will re-enable Shape Dynamics as well. "Size Jitter" should still be set to 100%. Now take a look at the preview of the brush at the bottom of the Brushes palette:

With the brush stamps further apart thanks to the changes we made to the "Spacing" option, we can now clearly see the effect that "Size Jitter" has on our brush. With a value of 100% for jitter, the brush never gets any larger than 19 pixels, but it is allowed to be virtually any size smaller than 19 pixels.

If I set the jitter value back down to 50%, we can see in the preview below that the brush never gets smaller than 50% of its maximum size, although it can be any size in between:

And if I set the jitter value back down to 25%, we can see the brush never dropping below 25% of its maximum size, but again, it can be any size in between:

Controlling The Photoshop Brush Size Ourselves

Now that we've seen how we can have Photoshop randomly change the size of our brush as we paint using the Size Jitter controls, let's look at how we can control the size of the brush ourselves with absolute precision, using the options found in the "Control" drop-down box. Click on the down-pointing arrow to view the list, as shown below:

Starting from the top, we have "Off", "Fade", "Pen Pressure", "Pen Tilt", "Stylus Wheel", and "Rotation". Of these, "Pen Pressure", "Pen Tilt", "Stylus Wheel", and "Rotation" all require you to have a pen tablet installed on your computer in order to have these options affect your brush. In an apparent attempt to confuse you, Photoshop will still allow you to select these options from the list even if you don't have a pen tablet installed, and it will even show you a preview of how the option will affect your brush in the preview box at the bottom of the Brushes palette. When you go to paint though, the option will have no effect on the brush. Photoshop is nice enough at least to give you a little warning icon to the left of the word "Control" if you've selected an option that requires you to have a pen when it doesn't detect that you have one installed, as shown below:

Let's look at each of these size control options, starting with the one at the top of the list, and the one that probably doesn't require much of a description, "Off".

Off

With Control set to "Off", you essentially have no dynamic control over the size of the brush as you're painting. The brush will remain at the size you chose for it when you selected the brush, at least until you manually change the size of the brush again yourself.

Fade

Of all the options for dynamic brush size control, "Fade" is the only one (other than "Off", anyway) that doesn't require a pen tablet to use, so if you don't have a pen tablet installed, it's the only real option you can select from the list that will have an effect on your brush when you go to paint, and the only option that won't give you the warning icon.

I'm going to leave my brush "Spacing" set to 100% for this discussion since it will be much easier to show you what Fade does if the brush "stamps" are not all jumbled together.

The way "Fade" works is that as you paint a stroke with the brush, the brush size will decrease, starting with the maximum size of the brush and then getting gradually smaller until it reaches a size of 0 pixels. How long it takes for the brush to reach a size of 0 pixels is controlled by the number of steps you specify in the input box to the right of the drop-down box where you selected the "Fade" option. A "step" is one brush stamp on the canvas. If you recall from our discussion above about how Photoshop paints with the brushes, rather than painting a continous stroke, it actually "stamps" the canvas with the brush shape at regular intervals which are set by the "Spacing" value in the Brush Tip options. This is why I've left my Spacing value set to 100% for this, so we can easily see the steps as Photoshop makes the brush size smaller and smaller.

By default, the number of Fade steps is set to 25 . This means that Photoshop will take 25 steps to decrease the size of the brush from its maximum size to a size of 0 pixels, as shown below:

If I was to change the number of steps to a smaller number, say 10:

Photoshop will take only 10 steps to decrease the brush size from its maximum size to 0 pixels:

And of course, if I was to increase the number to something much larger (you can have up to 9999 fade steps if you so choose), it would take that many steps to fade the brush out to a size of 0 pixels. I won't bother showing a screenshot for 9999 fade steps. You get the idea.

For some real fun, you can combine Fade with Size Jitter, which gives you a rather odd combination of randomness and precision control. Here, I've set my Size Jitter to a full 100% and I've set my Fade steps to 40:

And here's the result:

Since Fade was set to 40 steps, Photoshop still took a full 40 steps to reduce the brush size down to 0 pixels, but since I added a Size Jitter value of 100% into the mix, each step along the way was given a random size based on what the actual size for that step was supposed to be. The true power of Photoshop's dynamic brush controls lies in combining all the various options to create amazing brush effects, as we'll continue to see as we go along.

Pen Pressure

As the name implies, the "Pen Pressure" control option requires you to have a pen tablet installed on your computer. The way it works is very simple: the harder you press the pen down onto the tablet, the larger the brush size will appear, giving you the ability to create very elegant brush strokes with narrow beginnings, wide middles, and then back to narrow again at the end, as the preview in the Brushes palette shows (I've set my brush Spacing back down to the default value of 25% to give the brush stroke a more naturally flowing appearance:

Pen Tilt

"Pen Tilt" is another way we can control the size of the brush dynamically while we paint but that requires you to have a pen tablet installed. Rather than controlling the size of the pen based on how hard you're pressing the pen into the tablet, Pen Tilt controls the size according to how much you tilt the pen. With the pen at a 90 degree angle with the tablet (standing straight up), the brush size will be at its smallest, and will gradually increase in size the more you tilt the pen up, down, left, or right.

One additional option we have with Pen Tilt is "Tilt Scale", which controls how much larger the brush can become when you tilt the pen, up to a maximum of 200% larger. Pen Tilt is the only dynamic brush size control that uses Tilt Scale. It's grayed out when we select any of the other options, like Fade or Pen Pressure.

Stylus Wheel And Rotation

The last two options, "Stylus Wheel" and "Rotation", are two options for controlling the brush size that you probably won't use, and in fact, I can't use because my pen tablet doesn't have either of these features. As I said earlier, I can still select either of these options from the list, but they will have no effect on my brush while I'm painting. Also, Photoshop gives me the little warning icon telling me that I either need to buy myself a pen tablet with these features, or I should just forget about using them, which is exactly what I'm going to do.

And that's how Photoshop's dynamic size controls work for the brushes. But we've only just begun. Next up, we'll take a look at the dynamic Angle controls, and then we'll finish up our discussion of Shape Dynamics with a look at the Roundness controls.

Go to: Angle Controls  |  Go to: Roundness Controls