Black and White Conversions: Using a Gradient Map
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Step 5: Adjust Contrast With The Black And White Color Stops
We can also try to improve the overall contrast in the black and white image if necessary using the black and white color stops at either end of the gradient preview bar, although depending on your image, your black and white points may already be set to their optimal levels and no further adjustments should be made. You'll definitely want to keep Photoshop's Histogram palette open on your screen if you choose to adjust the contrast this way, since you'll want to make sure you don't clip any important shadow or highlight details in the image (see our How To Read An Image Histogram In Photoshop tutorial for more details). By default, the Histogram palette is nested in with the Navigator and Info palettes. If you can't see the Histogram palette on your screen, go up to the Window menu in the Menu Bar at the top of the screen and choose Histogram:
To pull the darkest areas of your image closer to pure black, simply click on the black color stop below the left edge of the gradient preview bar and drag it towards the right. As you continue to drag the color stop towards the right, more and more of the image will be darkened:
After dragging the black color stop towards the right, the darkest areas in my photo are now even darker:
However, if we look again at my Histogram palette, we now see a spike along the left edge of the histogram which means I've gone too far with the black color stop and pulled a lot of pixels in the image down to pure black, resulting in a loss of detail in the shadow areas:
Whether or not you have any room to move the black color stop without losing shadow detail will depend entirely on the image you're working on, which is why it's so important to keep an eye on the Histogram palette.
We can also push the lightest areas in the image closer to pure white by clicking on the white color stop below the right edge of the gradient preview bar and dragging it towards the left. As you continue to drag the color stop towards the left, more and more of the image will be lightened:
The lightest parts of my image are now even lighter after moving the white color stop:
However, if we look once again at my histogram, we see a spike along the right edge, which means we've lost detail in the highlights by going too far with the white color stop and forcing too many pixels to pure white:
Again, whether or not you have any room to move the white color stop without blowing out the highlights will depend entirely on your image, since every photo is different. For a better way to improve the overall contrast of an image, which should usually be done before converting the photo to black and white, be sure to check out our Improving Image Tone With Levels tutorial.
When you're satisfied with the results, click OK to exit out of the Gradient Editor dialog box, then click OK to exit out of the Gradient Map dialog box (Photoshop CS4 users can leave the Adjustments Panel open since there's no need to close out of it).
As we saw in the previous tutorial in this series when we looked at converting the image to black and white using a Hue/Saturation adjustment layer, nothing we've done to the image here is permanent. The entire black and white effect we've created is contained within the Gradient Map adjustment layer itself, while the original image remains safe and unharmed on the Background layer below it. If at any time you want to view the full color version of the image once again, simply turn the Gradient Map adjustment layer off by clicking on its layer visibility icon (the "eyeball" icon) on the left of the adjustment layer in the Layers palette:
Turning the adjustment layer off instantly restores all the color in the image:
Click again on the layer visibility icon to turn the Gradient Map adjustment layer back on and return to the black and white version.
Up next, we'll look at how we can use Photoshop's Luminosity blend mode to create a black and white version of our photo by simply ignoring the color, and we'll see how we can improve upon the initial results with a couple of additional blend modes and a layer mask!
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