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Wednesday, March 21, 2012

Adobe Photoshop Lightroom Tutorial - Part XXII - Adjustment Brushes

Part I - Index and Introduction

A couple of posts ago we introduced graduated filters and saw how they can be used to quickly apply a wide range of adjustments in a picture, mimicking and enhancing the behaviour of physical graduated filters we use to attach to our lenses.

The only problem with graduated filters is intrinsic to their behaviour: as we've seen, you basically set the filter axis (a straight line) and the adjustments are applied on the part of the image contained on the half-plane defined by the filter axis and direction. Although other geometries are possible, most physical graduated filters work exactly like this:

Colored and Graduated Filter (Hoya)

This kind of filter geometry is excellent (and easy to use) if you've got a straight line over which to lay the filter axis, such as the horizon. However, things get tough if you haven't got it: it's sufficient that even a small portion of the image unavoidably intrudes into the filtered zone (such as a mountain and a tower bell) and you'll end up with undesired results.

Look at the following image:

The Hague - Peace Palace

I took this picture on a trip to The Netherlands: we passed in front of Peace Palace, in The Hague, we stopped our car and I tried to take some shots from the only feasible position (the palace was closed). I couldn't wait for the sun to be in a better position, and this is the result: the sky is too bright with respect to the palace.

If I had used a graduated filter to stop down the sky, pretty much of the clock tower on the left would have darkened as well, which is unacceptable, since it's part of the picture's main subject. There are many solutions to this problem: I could have bracketed the exposure and blended multiple images together, for example. In this case, however, I could retrieve sufficient details in the shadows without blowing the highlights, which makes this image feasible to be fixed in post-production.

Adjustment Brushes

An adjustment brush offers the same set of adjustments of graduated filters:
  • Color temperature and tint.
  • Basic tone controls: Exposure, contrast, highlights and shadows.
  • Clarity.
  • Saturation.
  • Sharpness.
  • Noise.
  • Moiré.
  • Color.

The fundamental difference is that you can brush in the adjustments exactly where you need them. This is the adjustment brush panel in the Develop module, that you can open in  using one of this methods:
  • Selecting the Tools/Adjustment Brush menu item.
  • Selecting the graduated filter icon on the tool strip (described in a previous post).
  • Using the 'K' keyboard shortcut.
Adjustment Brush Panel

In the Mask section of the panel, you can choose whether you're creating a new brush or editing an existing one. If the picture has been applied other adjustment brushes, you can select them using their circular grey handle, which appears in the place you apply the first stroke of a brush:

Brush Handle in a Picture

Using the Effect drop down menu you can select an available preset. Lightroom ships many of them, and you can also save your own should a brush configuration be used often in the future.

A brush configuration can be applied using the adjustment sliders it offers. Adjustments can be modified at any time and the configuration change will be immediately reflected on the picture.

To brush an effect into the picture, you've got to select the brush properties in the Brush section of the panel, which are used to mimic the properties of a physical brush:
  • Size: the size of the circular area where the adjustment is applied.
  • Feather: the size of the "ring" around the brush where adjustment will be gradually faded to zero. A feather of 0 will produce a perfectly round shaped "hard" brush. The greater the feather, the smoother the brush transition at its edge.
  • Flow: the rate of application of the effect. 
  • Density: the amount of transparency of the brush stroke.

Flow and density are more useful when you're brushing in using the mouse. If you're brushing in using a pressure-sensitive device, such as a pen tablet (which is something I strongly recommend for advanced adjustments. See more at the end of this post), flow becomes less important since you can achieve the same effect applying different pressures on the pen.

The brush Auto Mask feature is often overlooked, but it's feature of paramount importance: it confines brush strokes into zones of similar colors. It's useful to auto-detect the edges of the area you're brushing in and it can incredibly speed up your workflow.

Applying an Adjustment: Some Initial Tips

When applying any adjustment, you want it to look natural. As a rule of thumb, strong gradients very seldom do, so that the following tips apply:
  • Start with "soft" brushes: relatively big sizes and some feather will help you achieve smooth adjustments with soft edges.
  • When brushing around an edge between zones with very different luminosity, try to avoid producing halos. Sometimes is better having the adjustment overlap the edge into the zone where the applied adjustment is less noticeable. If you're applying a burning, or darkening, effect (such as in this case), the darkening will be less noticeable when overlapping into the darkest zone rather than having a bright halo around the edges.
  • When possible, use the Auto Mask feature described in the following sections.

Auto Masking

To fix the sky in the previous picture I can brush in an exposure adjustment. As a starting point, I will try brushing in a -1 exposure adjustment. Since the sky is a pretty big portion of the image, I will brush in the adjustment starting with a pretty big and opaque brush with a relatively big feather.

Since the edge between the sky and the Peace Palace is quite irregular, it would be very time expensive trying to mask it manually without producing harsh transitions or halos around the edge. Since I'm brushing over the sky, which is pretty uniform in color and much lighter than the palace, I will turn the Auto Mask feature on and have Lightroom auto-detect the edges between the sky and the surrounding objects which, in this case, have a pretty irregular edge.

When you're brushing an adjustment, sometimes it's not easily discernible where the adjustment has been applied. In that case, you can turn on the Show Selected Mask Overlay feature (found on the bottom of the image), that will highlight the brushed in zones in a different color:

Showing a Brush Overlay Mask

Alternatively, you can use the following alternatives:
  • The Tools/Adjustment Brush Overlay menu and sub-items.
  • Using the 'O' keyboard shortcut.
Depending on your picture, not even the default mask overlay color couldn't be easily discernible: for this reason, Lightroom can cycle through a set of different colors (red, green and grey). To quickly cycle through the available options you can:
  • Use the Tools/Adjustment Brush Overlay menu and sub-items.
  • Us the 'Shift-O' keyboard shortcut.

In the following detail you can see the brush overlay mask highlighted in green:

Brush Overlay Mask

As you can see, Lightroom made a great job detecting the edges between the sky and the palace and only few correction are required.

To erase part of the brush overlay mask, in case you stepped over a zone you don't want to adjust, you can remove it from the brush mask simply selecting Erase in the Brush configuration field and brush out the undesired zone.

The result brush overly mask and the resulting image are the following:

Final Brush Overlay Mask Over the Sky

Final Image

As you can see, the final brush mask over the sky is nearly perfect and I only applied minor tweaks to it. In less than a few minutes, this step of the processing was done. In the final image, besides stepping down the sky about 1 f/stop, I also applied the following adjustments:
  • I added some clarity, to enhance the local contrast and make the clouds pop-up (the day was a bit foggy).
  • I raised the saturation a bit (+20): since the sky is blue, raising a bit its saturation will also contribute to the darkening effect. 

Other Common Adjustment Scenarios

The limit to the range of adjustments you can brush into your pictures is set only by your creativity. However, here are some common scenarios I often uses adjustments brushes in:
  • Enhancing the iris of a model: increasing exposure, clarity and saturation.
  • Whitening the sclera (the "white of the eye") of a model: increasing exposure and decreasing saturation.
  • Whitening the teeth of a model: increasing exposure and decreasing saturation.
  • Softening the skin of a model: decreasing clarity.
  • Burn (darken) a sky.
  • Dodge (lighten) part of an image to recover details in shadows too deep.
  • Modify the contrast in selected parts of an image, such as clouds or fog.

You can have a look at these posts for more information and further example:

Use a Graphics Tablet to Get Better Adjustment Brushing

Graphics tablets aren't commonly found on the desk of amateurs, let alone common users. However, they're devices that can drastically improve both the quality and the range of adjustments you apply in post production. Nowadays, an entry level tablet (such as Wacom's Bamboo, starting at about $60) can cost as much as a good mouse or trackpad and, in my opinion, is a much better investment for an amateur photographer.

Even smaller graphics tablets will give you a degree of control over your brushing that's simply unmatchable using a point-and-click devices such as a mouse (or a trackpad). Also, once you get used to them, chances are you'll use them as your only pointing device as well, at least when you're at your desk.

At the bottom of this post you'll find some Amazon's link to some entry level tablets where you can start your investigation from.


Adjustment brushes are an easy way to locally apply a wide range of adjustments offered by Lightroom. Any opportunity not to leave Lightroom to edit a picture in an external program is a great advantage in terms of speed, efficiency and flexibility. Not only you're able to apply a wide range of adjustments without leaving the program, but you're also able to modify them on the fly taking advantage of Lightroom's non destructive workflow.

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