Convert HDR to Grayscale with a Gradient Map
Most people don’t think of using gradient maps to convert high dynamic range (HDR) images to black and white (also known as grayscale), but the results are very good. A gradient map is nothing more than a mask that turns everything beneath it to grayscale.
In Photoshop Elements, follow these steps:
Choose Layer→New Adjustment Layer→Gradient Map to create an adjustment layer.
This calls up the New Layer dialog box. Click OK to continue.
If necessary, select a gradient from the Adjustments panel.
If the gradient (you can see it in the Adjustments panel in the figure) runs from black to white, you don’t need to change it. If it’s something else, select Black, White from the Gradient Map drop-down list.
Click OK to close the dialog box and apply the gradient map as an adjustment layer.
If you don’t want the hassle of an adjustment layer, right-click the layers in the Layers palette and choose Merge Visible. This combines the layers into one. If you do want the hassle (say you want to come back and edit the adjustment), remember to make a merged copy to lock in the effect before you continue.
You can create part color and part black-and-white images in Photoshop Elements by erasing areas of a Grayscale Map mask. Select the Eraser and make sure your background color is black (black areas of the mask allow the lower layer to show through unaffected).
Click the mask to select it, and then erase areas on the image you want to remain in color. Make a mistake? Switch to the Brush with white as the foreground color, and paint white in the mask to reapply the black and white adjustment.