Here’s a typical rookie photographer mistake. You focus so much on your subject that you lose track of what is around it.
And sometimes you end up making photos where the background distracts from your subject.
This article will teach you how to blur the background in Lightroom in the post-processing stage in exactly such cases.
A Word Before You Blur
Of course, it’s always easier if you don’t need to make this adjustment in post at all. Getting it right at time of shooting can save you the work.
The sooner you learn to pay attention to a subject’s surroundings while shooting, the better. In general:
1. If the subject is in the background, the foreground must contain an element of interest.
2. If the subject is in the foreground, the background should not be so distracting as to divert the viewer’s eyes.
Sometimes it is possible to fix things up in post-production. You can add interesting elements in the foreground, thus creating a composite image. Or you can blur the background so it’s less distracting and make your subject stands out more.
Read on to learn how to blur a distracting background in Adobe Lightroom. And if you are interested to know more about how to get it right in camera, check out the bonus section at the end.
Fixing the Background in Post-Production
Let’s consider this image of a gorilla I shot at a zoo using my Sony RX100 Mk2 compact camera. This Sony is a great walk-around camera. The only downside is the unimpressive f/4.9 minimum aperture value when zooming all the way in.
The Sony is a 1″ crop sensor camera. The depth of field (DoF) at 90mm and f/4.9 is equivalent to that of a 236mm lens at f/10.9 on a full-frame camera. Unsurprisingly, everything is basically in focus.
I tried to convert the image to black and white. With all the ropes and wood, the background is still distracting and the gorilla gets lost in it.
Let’s fix this using a digital blur effect to create a blurred background.
Adobe Lightroom or Adobe Photoshop?
To be honest, while Adobe Lightroom is a wonderful RAW developer, it does not excel at this kind of editing.
Adobe Photoshop is the standard for these manipulations. You can rely on layers and tools to quickly create and refine masks, to apply effects such as Gaussian blur and lens blur and to create a bokeh effect.
With Photoshop, it took me about 3 minutes to mask out the gorilla, and blur the background.
In the original image, your eyes go back and forth between the bog knot and the gorilla. In the edited image the first thing to capture your eyes is the gorilla.
Achieving a similar result in Lightroom took me more than 1 hour.
The good news is that if you already have a subscription for Adobe Lightroom CC, you can download and use Adobe Photoshop for free. A great replacement for Photoshop at an affordable price is Affinity Photo from Serif.
Blurring the Background in Lightroom
Despite preferring to use Photoshop for these kinds of jobs, I reckon Adobe Lightroom is quite capable of blurring the background. It’s particularly useful if you have a slightly blurred background to begin with.
With no tools to help you mask the background, you have to manually create one by painting the background with an adjustment brush. I like to use the brush tool for this.
Lightroom Brush Tool
The brush tool is used to apply an effect to a part of your image.
- The mask part of the brush panel lets you create a new mask or edit an existing one.
- In the Effect section of the panel you can choose a preset or manually create your effect. (Note: You can change the brush effect at any time, but it will also affect what you have already painted.)
- The Brush section of the panel lets you define effects for two brushes, having different size, feather, flow, auto mask and density properties, and one erase brush, to erase parts of your mask.
- The brush properties can be changed at any time and will have no effect on the parts already painted.
- Size: sets the size of the brush
- Feather: sets how soft or hard the brush is
- Flow: sets the strength for the brush. Use a value lower than 100 to slowly build up the effect while painting on the same area
- Auto Mask: toggle on to help you to follow borders when you paint
- Density: sets a cap for the max strength of the brush
How To Select the Background
Begin by selecting a sharpening adjustment brush tool. Then crank the sharpening slider all the way to -100 and start painting over the background. You do not need to be precise at this stage.
Use the keyboard shortcut ‘o’ to show or hide the mask (displayed in red). This way, you’ll see better where you are painting. Note than while the mask is on, the brush effect on the image is not shown.
Once you have a coarse mask, start working around the edges. Tune the size/flow/density and feather for your brush to refine the mask edges. Sometimes, the auto mask option can help you in this.
Eventually you will need to use the Erase brush to clean up your subject. That’ll ensure that the blur effect is applied only to the background.
Tip: Don’t be afraid to zoom in. You can quickly navigate the image by pressing the space bar while dragging the image around with the mouse.
Tip: For realistic blur, remember that the amount of blur is gradual and increases with the distance from the focal plane. All the objects on the focal plane must be kept sharp.
After a long paint/erase process, you end up with a pretty decent mask.
Because the red colour of the mask can be hard to see and does not let you see the effect of the brush on the image, double-check the quality of your mask by setting the exposure for the brush to -2/-3 EV.
Once you hide the mask, you will see the parts you painted on are heavily underexposed, making it easy to spot imperfections that need to be fixed.
How To Apply The Blur
Once you are happy with your mask, reset the exposure of your brush to zero and be sure the sharpness slider is set to -100. This will introduce some degree of lens blur.
Tip: Do not touch the clarity slider (yet). Pushing the clarity all the way down will remove all the contrast from the mid-tones leaving you with a soft and dreamy background that screams ‘fake’!
Before moving on, consider making some adjustments to the background, such as dodge/burn, reduce highlights, apply contrast, etc.
How To Increase The Amount Of Blur
Setting the sharpness to -100 did introduce a certain amount of lens blur, but not much.
The good thing about Lightroom is that you can duplicate your adjustment brush by simply right-clicking on the brush marker and selecting ‘Duplicate’.
This new brush has the same settings and mask as the previous one. Be sure all the sliders are set to zero except Sharpness, which must be set to -100.
From now on duplicate the brush as much as you need to build up the blur effect you are after.
Warning: Having many adjustment brushes in an image will slow down Adobe Lightroom performances and, when exported, it will create a jpeg file larger than usual.
The Final Retouch
After having finished blurring the background, you can now duplicate the brush one last time, slightly reducing the clarity (set the sharpness back to zero) to accentuate the blur.
Next, you can use the global settings or other selective adjustment tools to make the final adjustments to your image.
When you are happy with your image, the only thing left to do to is export the photo and share the results of your hard work.
Bokeh and A Bit of Theory
In photography, bokeh is the aesthetic quality of the blur produced by a lens in the out-of-focus parts of an images. Bokeh has also been defined as ‘the way the lens renders out-of-focus points of light’.
The ‘out-of-focus’ part of the bokeh definition given above depends on the depth of field.
The DoF, is the range of distances either side of the focal plane at which the focus is ‘acceptably sharp’. The focal plane is the distance from the camera at which the sharpest focus is attained—everything on that plane will be in focus.
Digital Blur Isn’t Always Ideal
The main difficulty in creating a realistic digital blur effect lies in reproducing the gradual increase of the blur as it gets further from the focal plane, as seen in the example below.
Bonus: How To Get It Right In Camera
Your camera sensor size will affect the DoF. For a given combination of focal length, aperture and subject distance small sensors give higher DoF than larger sensors.
The DoF can be modified as following:
- Aperture: double the f-number (e.g. move from f/4 to f/8) and the DoF is also doubled
- Subject distance: double it and the DoF increases by a factor of four
- Focal length: double it and the DoF is reduced by a factor of four
If you want to maximise DoF, so that most of your landscape will be sharp, then you should use high f-numbers, short focal length, and focus reasonably far away (a general rule of thumb says you should focus 1/3 into the scene).
If you want to minimise the DoF, to better isolate your subject from the background and have nice bokeh, then you should use small f-numbers, long focal length, and move closer to your subject.
Tip: If you are shooting portraits with natural light while outdoors, you can keep shooting wide open with fast lenses by using a 2 or 3 stop neutral density filter.
Finally, if you cannot reduce your DoF further but still need to blur the background, your last option is to increase the subject-to-background distance, if possible.