Making a Photo Gradually Fade from Color to Grayscale with Photoshop

Layer masks are extremely powerful when it comes to blending multiple images so that one seems to dissolve into the others. I’m not going to show you how to use a layer mask to blend different images, but rather the same image — one in color and one in grayscale.
1. Open a copy of your favorite color image.
The subject matter isn’t critical here, so feel free to whip out that old prom picture.
2. Choose Image➪Duplicate.
Accept the default name and click OK in the dialog box.
3. With the duplicate image active,
choose Window➪Channels.
4. View each of the channels to find the one that gives you the best grayscale image.
The Red channel gives the best contrast for the portrait in my example. Skin tones tend to have a lot of red in them, and the Red channel usually provides the best grayscale image.
5. Choose Image-->Mode-->Grayscale and click OK in the Adobe Photoshop dialog box.
Photoshop has now stripped the color from the image. This is only one way to convert a color image to grayscale. There are others, usually yielding better results — converting to Lab Color mode, picking a single channel, using the Channel Mixer. Feel free to choose your own method.
6. Choose Window-->Layers. With the Move tool and holding down the Shift key, drag and drop your grayscale image onto your color image.
This action automatically creates a new layer from the grayscale image. (By holding down the Shift key, you keep the two images perfectly aligned.
7. Close your duplicate image.
8. Press D for default colors.
This gives you a black foreground swatch and a white background swatch in your Toolbox (more formally known as the Tools palette). Now, I show you how to use one of my favorite techniques, a blackto-white gradient, on the layer mask.
9. Make sure that Layer 1 is the active layer in the Layers palette. Click the Add Layer Mask icon at the bottom of the palette.
It’s the icon that looks like a dark square with a white circle on top. Photoshop adds a second thumbnail on your layer, indicating that a layer mask has been applied. A layer mask acts like a piece of clear acetate over your layer.
10. Select the Gradient tool. Then select the default gradient of Foreground to Background.
To get the default gradient, click the Gradient picker in the Options bar and select the first gradient. It should be a gradient of white to black because it’s based on the current foreground and background colors, which reverse when you select the Layer Mask thumbnail.
11. Drag the gradient from the top of your image to the bottom.
Or from left to right. Or at a diagonal. It’s your call.
12. Experiment with long drags and short drags. The angle and length of your mouse movement determine how the layer mask reveals the underlying image.
In my example, I dragged from the top of the image to the bottom and stopped about two-thirds of the way down. Where black appears on the layer mask, the grayscale image is hidden. Where white appears on the mask, the grayscale image shows through and everything in between allows the grayscale image to partially show. Although I used a linear gradient in my example, you can experiment with the other types as well. Radial gradients can provide some interesting effects.
13. When you’ve completed your mask, save and close the file.