We’ll be using Photoshop’s classic Brightness/Contrast feature in a selective way. Picture areas that need it better will be adjusted more. The key to do this is the Quick Mask feature.
Load the photo in Photoshop
Well, the picture does have an eerie feel. It is a bit dark, which is OK regarding the theme, but a bit of lightening would do it good. However, it should only be applied to the darker areas of the picture, the lighter ones should almost remain unchanged. Usual brightness increasing methods make all parts of the picture equally brighter. If you only want to work with areas of a certain brightness, you have to create a mask which excludes other parts from the adjustment.
Click the Channels palette, which shows the picture separated to color channels. In the case of digital cameras, the Green channel contains most of the lightness information, so you should choose this one. Press and hold Ctrl while clicking the small preview image of the Green channel. Now you have selected the brightest areas.
At the bottom of the Tools palette, click the indicated icon to switch on Quick Mask mode and make the previously selected areas visible and editable. Although the illustration doesn’t show it very well, light and dark areas are selected with a different intensity. This is indicated by a reddish veil, where redder areas are more opaque, and less red ones are transparent. The more transparent the mask, the stronger the adjustment will affect it.
In this example, the lighter areas show a weaker mask, so they will be affected more intensively by the lightening, while the darker ones to a lesser extent. If you want to edit the lighter areas, skip the next few sentences and go to Step 4.
In this example, our aim is to lighten the darker areas, so we have to invert the mask, so that the Quick Mask will be weaker (less transparent) there. Click Image/Adjustments/Invert.
As the selection usually has a sharp border, we need to blur the mask in order to provide a smoother transition for the adjustment to come. The mask can be edited in Quick Mask mode just like normally you would do with a picture. Of course, we are still in Quick Mask mode.
Click Filter/Blur/Gaussian Blur. On the dialog that appears, specify values suitable for blurring smaller details well, but leaving main themes still recognizable. As we’re working with a small image, a Radius of 5 pixels will do, but for large photos, you may have to set much higher values.
After finishing the blur, switch back to normal editing mode from Quick Mask. To do so, press Q, or click the icon next to the indicated Quick Mask one.
Now, the main point.
Click Image/Adjustments/Brightness/Contrast. Set the values here according to your taste and needs. As you drag the Brightness slider to the right, you’ll see that it is primarily the darker parts that get lighter. The same thing is true for the Contrast slider. Set both controls to values you like. In this particular case, +19 and +21 seemed to work best. Contrast needed to be adjusted only in order to make the picture, naturally bleaching a bit because of the lightening, more lively.
This is the end
As you can see, the lighter areas barely changed. We didn’t even modified lightness of the darker areas substantially (although we could have done so), but the changes are much more spectacular here.