PS Online Tutorial: Four Ways to Blur a Background

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There are four ways to blur a background, and each suits a different situation: a mask gives you the most control, the eraser is the quickest, the History Brush is the most flexible, and a path is the most precise. All four come with steps — just pick the one that fits the image you have open in Online PS.

Method 1: Layer mask + Gaussian Blur

The most intuitive and most widely used approach: blur the entire image first, then use a mask to bring the subject back to its original sharp state.

  1. Open the image and press Ctrl + J to duplicate the Background layer as Background copy.
  2. In Filter → Blur → Gaussian Blur, adjust the Radius and watch the preview until the background is blurred to your liking.
  3. At the bottom of the Layers panel, click Add Layer Mask (the third button) to add a mask to Background copy.
  4. Press B to switch to the Brush tool, set the foreground color to black (hide) and choose a suitable brush size.
  5. Paint gently along the model's outline on the mask with the black brush — black reveals the original (unblurred) layer, while the background keeps its Gaussian blur.
  6. For finer work, switch the foreground color to white (restore) or use a soft-edged brush for a gradual transition.
Tip: quick selection + mask
If the model's outline is complicated, first select the subject with the Quick Selection Tool (W), click Select and Mask → Output to Layer Mask, and only then apply Gaussian Blur. Much less work.

Method 2: Eraser + Gaussian Blur

This works purely through the interaction between the layer and the eraser, and it produces just as clean a foreground.

  1. Open the image and press Ctrl + J to duplicate the Background layer.
  2. Apply Filter → Blur → Gaussian Blur to the copy and adjust the radius to the blur level you want.
  3. Select the Eraser tool (E), increase the brush size in the options bar and set hardness to 0% (soft edge).
  4. Slowly erase over the model's body (which effectively restores the sharp original underneath) — you'll see the unblurred original layer show through.
  5. If the edges end up too hard, switch to a soft-edged eraser or use Feather (Shift + F6) to soften them.
Note: erasing directly on an already blurred layer permanently destroys that layer's pixels. If you may want to change the blur strength later, convert the layer to a Smart Object first (right-click → Convert to Smart Object) — then you're erasing a mask, not pixels.

Method 3: History Brush + Gaussian Blur

The History Brush pulls the original pixels back out of the History panel, which saves you the duplicate-layer step.

  1. Open the image and press Ctrl + J to duplicate the Background layer (working directly on the original layer is fine too).
  2. Apply Filter → Blur → Gaussian Blur to the copy and adjust to the blur level you want.
  3. Open the History panel (menu Window → History). Make sure the history state set as the source is the original image as it was first opened.
  4. In the toolbar, select the History Brush Tool, shortcut Y.
  5. Set the foreground color to black (it already is by default) and brush over the model area on the blurred layer — the brush writes the "as first opened" (unblurred) pixels back into that area.
  6. When you're done, the background stays blurred and the subject stays sharp.
Tip: using the History Brush's mask mode
In the top right of the History panel, switch the History Brush source to "sample from current layer" or "sample from original layer" for more flexible local restoration.

Method 4: Path + Gaussian Blur

Trace the foreground outline precisely with a path (Pen tool) — the right choice when you need very crisp edges.

  1. Open the image and press Ctrl + J to duplicate the Background layer.
  2. Select the Pen Tool (P) in the toolbar and carefully trace the model's outline.
  3. When the path is complete, press Ctrl + Enter (or right-click the path → Make Selection) to convert it into a selection.
  4. Press Ctrl + Shift + I to invert it — the selection is now the background area.
  5. With the selection still active, apply Filter → Blur → Gaussian Blur and adjust the radius until the background is blurred to your liking.
  6. Click anywhere to deselect (Ctrl + D). Done.
Also: a faster path-to-selection route
If you'd rather not use the shortcut, click the Convert Path to Selection icon at the bottom left of the Paths panel.

A few final notes

  • If you want to try several methods in the same file, save it as a PSD first (File → Save as PSD) so you can always go back.
  • You can step back and forth through the blur at any time in the History panel, or apply Gaussian Blur as a Smart Filter (right-click the layer → Convert to Smart Object) so the edit stays non-destructive.

References

  • Online PS
  • Adobe official documentation
  • PS tutorial sites
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