Blur and sharpen effects in Video by Zaweba

Blurs do more work in a video edit than you might think. They hide faces and number plates, soften backgrounds behind titles, suggest speed, fake a shallow depth of field and smooth over the joins in a composite. Video by Zaweba has a wide set: gaussian, directional, zoom, spin, tilt-shift, sharpen, unsharp mask and smooth, plus lens (bokeh), channel, compound and focus blurs.

Choosing the right blur

Gaussian blur is the plain, even softening that most people mean when they say blur. Use it for backgrounds behind text, for hiding something, and as a general tool.

Directional blur smears the picture along one direction. It suggests motion, so a still picture of a car can look like it is moving, or a whip of a camera can be exaggerated.

Zoom blur streaks outwards from a centre point, like the camera rushing forwards. Spin blur streaks round a centre, like a wheel turning. Both are dramatic and suit transitions and music videos more than everyday scenes.

Tilt-shift keeps a band of the frame sharp and blurs above and below it. On a high wide shot of a street or a town, that makes the scene look like a model, which is a popular effect.

Lens blur imitates how a real lens renders out of focus areas, with bright points turning into soft discs of light, often called bokeh. It is a more convincing background blur than gaussian. Focus blur and compound blur let the amount of blur vary across the frame, which is the way to fake depth of field. Channel blur blurs the red, green and blue channels by different amounts, a subtle effect that can soften colour noise or make a dreamy, slightly misaligned look.

Hiding a face or a number plate

This is one of the most common jobs. Add a mask to the clip around the face, or use the Only inside mask option for the blur effect so it acts only inside the mask. Use gaussian blur with enough strength that nothing is recognisable. If the person moves, the mask tracking tools can follow them so the mask stays on the face, and checking the whole clip frame by frame is worth it before you export anything where privacy matters.

Sharpening without making it worse

Sharpen and unsharp mask both increase the contrast along edges so details look crisper. Unsharp mask, despite the name, is a sharpening tool with more control, and it usually gives a more natural result. Smooth goes the other way, softening fine texture while keeping edges.

Sharpening can't add detail that was never recorded. It can make a slightly soft clip look better, but on a properly blurry shot it just adds halos and makes noise more visible. Use it lightly and look at the result at full size, using the preview zoom if needed.

Blurs as part of the bigger picture

Blurs work well on adjustment layers. A soft blur over the bottom third of every shot in a section, with a mask, gives captions a calm background without touching the clips. Blur strength can be keyframed, so a shot can drift out of focus as a scene ends or a background can soften as a title appears.

Several blurs are also used inside other tools. Some transitions use blur, and the 360 degree group has its own blur, made so the join where a 360 picture wraps round doesn't show.

Where blurs go wrong

Edges are the giveaway. A blur limited by a mask with a hard edge looks cut out. Give the mask some feather so the change fades in.

Heavy blurs on long clips can slow the preview. Check the Effects tab badges and expect lens and compound blurs to take more time than a plain gaussian.

Last, think about whether blur is the honest choice. A strong fake depth of field on every shot gets tiresome. Used where it helps the story, the blurs in Video by Zaweba are some of the most useful effects in the app.