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This lesson demonstrates how to replace a background, utilising RGB Channels, and the Magic Wand Tool. You will find the image I am working with Here. Unzip the file and open the image onto Photoshop’s workspace ready to utilise.
Undo and Navigation Steps
Two ways of undoing steps are from the top menu, Edit then Step Backwards. Alternatively, click a previous snapshot in the History Palette.
Navigate (zoom in and pan) your image using the Navigator Palette,
or the Zoom Tool. 
Activate The Hand Tool by tapping the Spacebar, keeping the Spacebar pressed, pan your image in the usual way. 
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Open your start image onto Photoshop’s workspace.
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Then from the Layers palette, double-left-click the Background layer, and reply OK to the New Layer dialogue box. Your photograph’s layer will change from Background to Layer 0, and the padlock will be removed - making your image editable.
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Ensure the Channels palette is visible, (it shares a palette with Layers). To display the palette, from the top menu, choose Window then choose Channels, or Layers. Now, click to activate the Channels tab.
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You will notice Channels separates your image’s colours into RGB, Red, Green or
Blue. Click the individual Red, Green and Blue channels - and find a channel that provides the best contrast between the edge of the sunflower and its background. You will find the Blue channel provides the best contrast, however, when using your own image, click a channel that suits your photograph.
 
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You may find this easier if you zoom into your image. Now, from the toolbar, activate the Magic Wand Tool, and set the following attributes.
Ensure Add to selection is active.
Then left-click once outside the sunflower, as shown below. The upper portion of the sky will be selected (isolated) with a selection by marquee, as illustrated below.
Now, move around the image, continually left-clicking, until the entire sky is isolated with a marquee.
 
Note
An alternative way of selecting similar coloured pixels, is - while the marquee remains active, right-clicking the image, and choosing Similar from the drop-down list - continue left-clicking to select stubborn pixels.
Important
With either the Navigator Palette - or the Zoom Tool, zoom into your image, and ensure the selection marquee has surrounded your element, as close as possible. If it has not, as illustrated here.
Simply activate the Magic Wand and click inside the un selected area, to surround it with a marquee. 
Navigate your image, and ensure the marquee is tight around the flower’s edges.
Tip
If the following happens, and the marquee transcends the flower - or the marquee disappears altogether; from the top menu choose, Edit then choose Step Backwards. Alternatively, click an earlier snapshot in the History Palette.
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Now, from the top menu, choose Select then Modify then choose Expand. In the subsequent Expand Selection dialogue box, type 1 (Pixel) into the Expand By box, then click OK. This expands the marquee, so it is a close fit around the sunflower.
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Then from the top menu, choose Select then choose Modify then choose Smooth. In the subsequent Smooth Selection dialogue box, enter a Sample Radius of 1 (Pixel), then click OK.
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From the top menu, choose Select then choose Feather. In the subsequent Feather Selection dialogue box, enter a Feather Radius of 1 (Pixel), then click OK.
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Now the preparation is complete, it is time to remove the sky. However, first, (still in Channels), click RGB, to display your image’s full colour.
 
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From your keyboard, press the Delete key and the sky will be deleted! Press Ctrl then D to remove the marquee.
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Now, zoom into your image and ensure there are no traces of blue sky surrounding the sunflower. To remove small areas, activate the Polygonal Lasso Tool - Polygonal Lasso Tool lesson here.
And with a Feather of 1, surround the blue areas with a marquee - then press the Delete key. (Press Ctrl then D to remove the marquee).
 
Tip
The Eraser Tool is equally useful in removing stray pixels, my Eraser Tool tutorial can be found here.
When you have removed all blue pixels, you are ready for the next step.
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Now you have cleanly removed the sky, its time to introduce it to a new background. To fill the background with a Solid Colour, Gradient or Pattern, from the top menu, choose Layer then choose New Fill Layer, and make your choice. My Fill Layer tutorial can be found here.
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Alternatively, open another image, then activate the Move Tool  - and drag your transparent sunflower onto your second image.
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From the top menu, choose Layer then choose Flatten Image, and link here to save your image.
Wendi E M Scarth. Top of Page - Home.
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