Replace a Sky with Simple Selection Tools in Photoshop

How to Replace a Sky Using Simple Selection Tools in Photoshop

This is the first entry in a three-part series on selections, one of the most fundamental and powerful concepts in Photoshop. Rather than jumping straight to a single “best” tool, this tutorial walks through Photoshop’s simple selection tools one at a time on a real sky-replacement project, showing where each one is strong and where it starts to struggle.

Understanding What a Selection Does

Before touching any specific tool, it helps to see exactly what an active selection changes about how you can edit an image.

1. Bring In a New Sky

   Use the Move tool to click and drag a new sky image into your document, then press Ctrl/Cmd + T to scale it to fit.

2. Make a Selection and Paint Inside It

   Create a new layer, use the Rectangular Marquee tool to draw a selection, then paint with the Brush tool anywhere on the canvas — the paint only appears inside the selected area.

3. Deselect to Compare

   Press Ctrl/Cmd + D to deselect, then paint again to see that without an active selection, paint shows up everywhere you click.

Using the Rectangular and Elliptical Marquee Tools

The Marquee tool group includes a rectangular option and an elliptical option, and both support the same modifier keys for building more complex selections.

4. Draw a Rectangle or Square

   Click and drag with the Rectangular Marquee tool for a rectangle, or hold Shift while dragging to constrain it to a perfect square.

5. Reposition While Dragging

   Hold the spacebar while a selection is still being drawn to move it into place, then release spacebar to continue resizing.

6. Add, Subtract, and Intersect Selections

   Hold Shift while drawing a new selection to add it to the existing one, hold Alt/Option to subtract, or hold Shift + Alt/Option together to keep only the intersection of the two areas.

7. Switch to the Elliptical Marquee for Curved Shapes

   Select the Elliptical Marquee tool for oval selections, holding Shift for a perfect circle — the same add, subtract, and intersect shortcuts work identically here.

These Modifier Keys Work on Every Selection Tool

Shift to add, Alt/Option to subtract, and Shift plus Alt/Option to intersect aren’t unique to the Marquee tools — they apply the same way across the Lasso and Magic Wand tools too, which is what makes it possible to combine several different selection tools into one final selection.

Cutting Out Mountains with the Lasso Tool Family

A rectangular or elliptical selection isn’t well suited to an irregular shape like a mountain range, which is where the three Lasso tools come in.

8. Load a Rough Selection into a Layer Mask

   Make an initial rough selection (even a simple rectangle) around the sky, then click the layer mask icon to load that selection directly into a mask. The selected area stays visible and everything else is hidden, so press Ctrl/Cmd + I to invert the mask: now the mountains show and the sky is hidden. White areas on a mask stay visible, black areas are hidden.

9. Draw Freehand with the Regular Lasso Tool

   Press L for the Lasso tool and draw directly along an irregular edge like a mountain ridge, then go to Edit > Fill and fill the selection with black on your layer mask to hide that area.

10. Use the Polygonal Lasso Tool for Straight Edges

    Switch to the Polygonal Lasso tool (found under the regular Lasso) for subjects with straight edges, like architecture. Click once per corner to connect straight line segments, then press Enter to close the selection.

11. Hold Alt/Option to Switch Between Lasso Types Mid-Selection

    While using either the regular or Polygonal Lasso tool, hold Alt/Option to temporarily switch to the other type — useful for a subject with both curved and straight sections.

12. Try the Magnetic Lasso for Automatic Edge-Snapping

    Select the Magnetic Lasso tool and move your cursor along an edge; it automatically places points that snap to the boundary it detects. Press Delete or Backspace to remove a misplaced point and back up.

Choosing Between the Three Lasso Tools

The regular Lasso tool is best for organic, irregular edges where natural hand variation isn’t a problem — a jagged mountain ridge, for instance. The Polygonal Lasso tool is better for subjects with genuinely straight edges, like buildings. The Magnetic Lasso tool trades some accuracy for speed, snapping to detected edges automatically, which makes it a reasonable starting point when you don’t need a perfectly precise selection.

Point Sample Versus Averaged Sampling

A Point Sample setting reads the exact single pixel you click on, which can make a selection overly sensitive to small noise or grain. A 3×3 or 5×5 average instead reads a small cluster of pixels around your click, giving a steadier, more representative starting color for the selection to expand from.

Speeding Up Simple Areas with the Magic Wand Tool

For a relatively uniform area like open sky, the Magic Wand tool can select based on color similarity far faster than tracing an edge by hand.

13. Set Your Sample Size and Tolerance

    In the options bar, choose a sample size like 5×5 Average, and set the Tolerance value — a lower tolerance selects only very similar pixels near your click point, while a higher tolerance selects a broader range of similar colors.

14. Click to Select a Similar-Colored Area

    Click once on the area you want to select. The tool expands outward from that point until it hits a significant color boundary.

15. Toggle Contiguous On or Off

    With Contiguous checked, the selection stops at the first boundary it finds. Unchecking it selects every similar-colored area throughout the entire image, connected or not.

16. Build Up the Full Sky Selection

    Adjust Tolerance up or down and hold Shift to click-add additional areas until the entire sky is selected right up to the edge of the mountains.

Sample All Layers for Complex Documents

The Magic Wand’s Sample All Layers option lets it read color information from every visible layer in your document rather than just the currently selected one, which matters once your composite has multiple images stacked together rather than a single flat photo.

Combining Multiple Tools on One Selection

None of these tools has to work alone — the real advantage of Photoshop’s selection tools is that you can switch between them freely while refining the same active selection.

17. Subtract Mistakes with the Lasso Tool

    If the Magic Wand grabbed too much (part of the mountains, for instance), switch to the Lasso tool, hold Alt/Option, and draw over the unwanted area to remove it from the selection.

18. Add Missed Areas with Any Tool

    Switch to the Rectangular Marquee, the regular Lasso, or any other selection tool, hold Shift, and add whatever area was missed — there’s no need to stick with the tool you started with.

19. Re-enable a Disabled Layer Mask

    If a layer mask shows a red X, meaning it’s temporarily disabled, hold Shift and click on the mask thumbnail to re-enable it before continuing.

20. Fill the Finished Selection with Black

    With the mask thumbnail selected (indicated by a white border around it), go to Edit > Fill and fill your completed selection with black to hide that area and reveal the new sky underneath.

Refining the Final Edge with Select and Mask

A selection built from several different tools can still leave a slightly jagged, obviously cut-out edge — Select and Mask is the last step for softening that transition.

21. Open Select and Mask

    With your layer mask selected, go to Select and Mask and switch the view to On Layers to see the effect directly on your composite.

22. Feather and Shift the Edge

    Add a small amount of feathering to soften the cut line, and use Shift Edge to expand or contract the selection slightly until it blends more naturally with the new background.

23. Add Contrast Carefully

    Add a touch of contrast back to the edge if needed, but avoid pushing it too far — too much contrast on a refined edge tends to look artificial rather than natural.

Common Mistakes to Avoid

The most common mistake is sticking with one selection tool for an entire complex shape instead of switching tools as the shape’s edge changes — a mountain range with both jagged ridges and straighter cliff faces is a good candidate for combining the regular and Polygonal Lasso tools rather than forcing one to handle everything. It’s also easy to skip the Select and Mask refinement step at the end, leaving a hard, obviously artificial edge where a small amount of feathering would have blended the composite far more convincingly.

Why This Approach Works

None of Photoshop’s simple selection tools is designed to handle every situation on its own — the Marquee tools are fast but geometric, the Lasso tools trade speed for shape flexibility in different ways, and the Magic Wand is powerful on uniform color but useless on detailed edges. Learning them as a set, with the same add/subtract/intersect logic working identically across all of them, is what actually makes selections practical: you’re not choosing one tool for an entire image, you’re picking whichever tool fits the specific edge in front of you at that moment and combining the results. That same combine-as-you-go approach carries forward into more automated selection tools as well, including the AI-assisted Select Subject and Refine Edges workflow covered later in this series.

Final Thoughts

Simple selection tools might look basic next to Photoshop’s more automated options, but understanding exactly how they add, subtract, and intersect is foundational to everything else selections are used for, sky replacements included. Get comfortable switching between the Marquee, Lasso, and Magic Wand tools on the same selection, and finish every cutout with a quick pass through Select and Mask — that combination handles a surprising range of real compositing work on its own. Part two of this series covers the advanced tools, Object Selection, Select Subject and Color Range, and part three, Refine Selections in Photoshop: Select and Mask Made Easy, cleans selections up with Select and Mask, hair included.

Quick Reference: Keys, Menus and Settings

• Add, subtract, intersectShift, Alt/Option, Shift + Alt/Option; hold Spacebar to move a selection while drawing
• Deselect or copyCmd/Ctrl + D deselects; Cmd/Ctrl + J copies the selection to a new layer
• Selection to maskClick the layer mask icon; Cmd/Ctrl + I inverts; Edit > Fill > Black hides more
• Lasso toolsL, Shift + L cycles; hold Alt/Option to switch Lasso and Polygonal; Enter closes, Delete/Backspace removes a Magnetic point
• Magic WandSample Size 5 by 5 Average, Tolerance 20 (down to 15 or 10), Contiguous on
• Mask on and offShift-click the mask to disable or enable it; Alt/Option-click to view it
• Refine the edgeSelect > Select and Mask, View: On Layers, Feather, Shift Edge, a little Contrast

No AI, no generative credits.