Table of Contents
Here’s an easy way to adjust exposure in f-stops, a fairly common task among photographers. The key to this technique is that the blending modes of the Wester and multiplication layers with an opacity of 38% produce an effect very similar to brightening or darkening a full f-stop. (Use 19% opacity for half-aperture settings, 13% for one-third aperture, and so on.) In this example, we darken the image by the value F-stop.
Create an aperture correction layer.
If you are working on a flat file, duplicate the background layer by choosing Duplicate Layer from the Layer menu.
If you are working on a layer file, create a new layer by choosing New > Layer from the Layer menu, and
Then press Command+Option+Shift+E (Mac) or Ctrl+Alt+Shift+E (Windows) to merge the contents of all visible layers into the new layer, leaving the layers below intact.
Apply global aperture correction.
Select the newly created layer in the Layers palette, and then set the blending mode to Multiply and the opacity to 38%. This darkens the image globally by an aperture number.Atlantic Eclipse Gaming/Studying/Working Desk, Durable Carbon Fiber Laminated Desktop, Heavy-Duty All-Steel Legs, Integrated Speaker Stands, Gadget Storage, Cable Management, PN 82050334 – Black
Add a layer map.
The global correction obscures too much of the vegetation of the waterline. To apply the fix locally, you must first add a layer mask by selecting Add Layer Mask from the Layer menu. In this case, the Discover All option is used, but choose the option that requires the least amount of color.
If you want to correct a small area, it is more efficient to choose Hide All and Color Correction than to choose Discover All and Clear Correction.
Note that when you add it, the layer map is automatically centered in the Channels palette, and the front and background colors are automatically set to black and white so that the layer map can be edited.
Limit the correction.
If the front color is set to black, use the Brush tool with a soft brush to delete corrections from areas where you don’t want to apply them. In this case, we paint with an opacity of 33% to reduce the correction of the waterline by 1/3 of the aperture.
This technique is suitable for many variations. After you limit the correction to the desired area of the image, you can vary its intensity by changing the opacity of the layer. For example, to correct two apertures, increase opacity from 38% to 76%.
You can also experiment with different techniques to limit correction. If the area you want to correct or protect is easy to select, you can create the selection before adding the layer map, and then use the Discover Selection or Hide Selection options. If you want to limit the correction to a specific tonal range, you can use the Blend options in the Layer Style dialog box to constrain the correction to the desired tonal range. For small local corrections, you can use the History Brush tool, where the source is set to the state of the current image and the brush mode is set to Raster or Multiply. This method is particularly useful for making sensitive corrections with the History Brush, which is defined at very low opacity values between 3% and 10%.