The three ways to control what shows through in Photoshop

Transparency in Photoshop works three different ways depending on what you are trying to do. You can change how see-through an entire layer is using the Opacity slider. You can erase parts of a layer to make them transparent using the Eraser tool. Or you can paint transparency onto a layer using a brush set to a lower opacity. Most projects use all three at different points — which one you need depends on whether you are adjusting the whole layer, removing specific parts, or blending edges.

The fastest route for most work is the Opacity slider, which lives in the Layers panel on the right side of your screen. Moving it left makes the layer more transparent; moving it right makes it more opaque (solid). This affects the entire layer at once, so if you need to make only part of a layer see-through, you will use the Eraser or a brush instead.

Key Takeaways

  • The Opacity slider in the Layers panel controls how transparent an entire layer is, from 0% (invisible) to 100% (fully solid).
  • The Eraser tool permanently removes parts of a layer to reveal what is underneath, and works best when you have a layer with a transparent background.
  • A brush set to lower opacity lets you paint transparency gradually onto a layer, which is useful for soft edges and blending.
  • Adjustment layers and layer masks let you control transparency without permanently changing your original image.

Using the Opacity slider for the whole layer

Open your image in Photoshop and look at the Layers panel on the right side of the screen. If you do not see it, go to Window in the menu bar and click Layers. At the top of the Layers panel, you will see a field that says "Opacity" with a percentage next to it — usually it starts at 100%.

Click on that percentage number and type a new value between 0 and 100, then press Enter. A value of 50 makes the layer half see-through; 25 makes it mostly transparent; 0 makes it invisible. You can also click and drag the slider itself to the left to lower the opacity gradually and watch the change happen in real time on your canvas. This is the fastest way to blend one image over another or to fade text into a background.

Removing parts of a layer with the Eraser tool

The Eraser tool permanently deletes parts of a layer, making them transparent. Find it in the toolbox on the left side of your screen — it looks like a pink eraser. Click it, then click and drag across the parts of your layer you want to remove. The erased area will show whatever layer is underneath, or a checkerboard pattern if there is nothing below.

Before you erase, check that your layer actually supports transparency. If your layer is labeled "Background" in the Layers panel, Photoshop will not let you erase to transparency — you will erase to white instead. To fix this, right-click the Background layer and choose "Convert to Layer," then try erasing again. You can also adjust the eraser's hardness and size using the options at the top of the screen. A soft eraser creates a gradual fade; a hard eraser creates a sharp edge.

Painting transparency with a brush

Instead of erasing all at once, you can paint transparency onto a layer gradually using a regular brush set to a lower opacity. Select the Brush tool from the toolbox, then look at the top of the screen where it says "Opacity." Lower this number — try 30 or 40 to start — and paint over the area you want to fade. Each stroke adds a little more transparency, so you can build up the effect slowly and see exactly where the fade happens.

This method is gentler than the Eraser tool because you can undo individual brush strokes and adjust how much transparency you add with each pass. It is especially useful for soft edges, blending two images together, or creating a gradual fade from solid to invisible. Make sure your foreground color is set to black before you start — the brush will paint with whatever color is in the foreground, but what matters here is that you are painting on the layer itself, not adding a new color.

Using layer masks to adjust transparency without changing the original

A layer mask lets you control transparency without permanently erasing or changing your image. Right-click any layer in the Layers panel and choose "Add Layer Mask," then select "White (Full Opacity)." A white rectangle will appear next to your layer thumbnail. Now when you paint with black on that mask, you are painting transparency — but you can always paint white again to bring the layer back.

Layer masks are useful when you are not sure about your transparency choices yet, or when you need to adjust them later. You can also use a gradient on a layer mask to create a smooth fade from opaque to transparent. Click on the mask itself (not the layer thumbnail) to make sure you are painting on the mask, then select the Gradient tool and drag across your image. The gradient will create a smooth transition from solid to invisible.

Controlling opacity for specific blend effects

The Opacity slider does more than just fade a layer — it also changes how the layer blends with the layers underneath. At 100% opacity, a layer covers everything below it. At lower opacities, the colors from the layers below start to show through and mix with the layer above. This is how you create effects like a watermark, a faded background image, or a subtle texture overlay.

You can also change the Blend Mode (the dropdown menu right above the Opacity slider) to change how the colors mix. "Multiply" darkens the image below; "Screen" lightens it; "Overlay" both darkens and lightens depending on the colors. Lowering the opacity of a layer set to Multiply or Screen creates a much more subtle effect than lowering the opacity of a Normal layer. Experiment with both the Blend Mode and the Opacity slider together to get the exact look you want.

Frequently Asked Questions

Can I undo an erased area after I close the file?

No — once you erase and save the file, that area is gone. If you think you might want to change your mind later, use a layer mask instead of the Eraser tool. A mask lets you paint the area back in by painting white on the mask, even after you close and reopen the file.

Why does my eraser not work on the Background layer?

The Background layer does not support transparency, so Photoshop erases to white instead of making the area transparent. Right-click the Background layer and choose "Convert to Layer" to unlock transparency, then try erasing again.

How do I make just the edges of a layer transparent?

Use a soft brush set to a lower opacity, or use a layer mask with a gradient. A gradient on a mask creates the smoothest fade. Paint black on the mask where you want transparency and white where you want the layer to stay solid.

What is the difference between lowering opacity and using the Eraser?

Opacity makes the entire layer see-through but keeps all the pixels intact — you can always raise the opacity back to 100%. The Eraser permanently removes pixels, so you cannot get them back unless you undo. Use opacity for temporary blending and the Eraser for permanent removal.