Seamless Selection

Perhaps the most basic process of using Photoshop is selecting an area in order to work on it. If you want to modify a particular section of an image, than you must select it. Novices love to use the Magic Wand tool, which selects areas of like color and density and has a variable tolerance feature which increases or limits the similarity of selection, but most professionals will use the lasso or pen tools, magnifying the image so they can carefully outline it. The trick to this and other methods of selection is to feather the selection so that there is not any noticable difference between modified and unmodified areas of an image. This way the viewer cannot tell which, if any, areas of your image were customized.

In the photograph of the botanical gardens waterfall (taken at Marie Selby Botanical Gardens in Sarasota, FL) the waterfall itself is in a shaded area. In order to brighten that area of the image only a very feathered selection (approx. 35 pixels on a 10 MB scan) was Lasso-ed around the waterfall so that there would be a soft transition between un-affected and fully-affected areas. This selection was then saved to an Alpha Channel or Mask which clearly shows the softness of the 35-pixel-feathered selection. The waterfall was then brightened seamlessly using a Levels adjustment, shown in the lower version.

The amount of feathering is determined by how defined the section is relative to the entire image. One pixel feathering is necessary for an area that is sharply defined - the less defined the section is the more feathering you need. The amount of pixels is, like everything else in Photoshop, resolution dependent. Four pixels at 100 dpi would be equal to 12 pixels at 300 dpi. Therefore, if you wanted to select an area that was blurred from motion, you could feather the area at least 6 pixels and more if the area is really undefined and/or if you are working at a high resolution. If you want to do a fade, like a vignette effect, you should feather your selection 30 to 100 pixels, depending on the resolution of your scan. Don't forget the standard features of the selection tools: Alt Key (Option key for Mac) to "rubberband" the Lasso tool, Shift Key to add one selection to another, Alt Key (Option key for Mac) to subtract from a selected area and no key to move a selection without moving what is in the selected area (you must have one of the selection tools chosen to do this). Also remember that you can Modify your selection under the Select menu - you can Expand or Contract up to 16 pixels at a time or even select the Border of a current selection.

Always consider saving your selection, especially if it took some time to create, so that you can Load it if further work on the selected area is necessary. Choose "Save Selection" under the Selection menu - a window will appear that will automatically ask you to save your selection to a New Alpha Channel. Hitting the Enter key or clicking on the OK button will create an Alpha Channel (or mask) that you can load at any time (choose "Load Selection" under the Selection menu and pick the appropriate channel or Control-click - Command-click for Macs - on the channel in the Channel Menu Window). Just like using the selection tools themselves, with the Shift Key down, you can add to an existing selection by loading any number of channels and, with the Alt Key (Option key for Mac) down, you can subtract from an existing selection by loading alpha channels (if the loaded selection intersects with the existing selection).

In the portrait of Tatyana the original scan (top) has very dark hair against the dark background. The hair was carefully selected with the Lasso tool using a rubberbanding method - Alt Key (Option key for Mac) - minimum amount of feathering - 4 pixels for a slightly soft edge. The selection was then modified along several areas of the perimeter by subtracting from the existing selection with the Lasso tool set with various amounts of feathering, from 8 pixels to 24 pixels. The selection was then saved to an Alpha Channel which is shown here. The hair was then brightened seamlessly using a Curves adjustment, shown in the lower version.

The Pen Tool

Another way to create a selection is by drawing a Path with the Pen tool and then change it to a selection and add feathering. The Pen tool was used to outline the hot air balloon in the photo above for putting it in front of another background. Advantages in using the Pen tool for making a selection: 1) If your selection is more geometric and sharply defined it can be more accurate to use the Pen tool (i.e., a curvelinear object is especially benefited by this approach); and 2) More critical selections are sometimes made with Paths because of the ability to refine the selection by using the directional arrows for minimum movement of points.

To see some creative "before and after" examples of photo scans that demonstrate seamless selection techniques click on the photo below to see a larger version..

Transitional Masks

The key to editing an area of an image in Photoshop is selecting it properly. I equate one use of transitional masks in Photoshop to burning a photograph as it is printed with an enlarger. When burning an area of a photograph to darken it, after the main exposure is completed, a common method is to use a black cardboard to allow the light to only expose that area of the paper which you want to be darker, constantly moving the cardboard so that there is no differentiation between burned and unburned areas. For instance, If you want to darken the top of your image like the sky in the Mountain Lake photo create a new channel by selecting all (Control, Command A) and Save Selection as a new Alpha Channel (bottom choice under the Select menu). Go to the new channel, make your foreground color black and your background color white and use the Linear Gradient tool, hold down the shift key and start your transition where you want the image to start getting darker and end your transition just past the top of the image. This will create a black to light grey transition as shown here. Go back to the composite channel and Load this selection channel (next-to-bottom choice under the Select menu). The selection marquee will show up at the midpoint of the transition and encompass to the top edge of the image. Then darken the area (or richen the colors) by adjusting levels, curves, brightness or saturation. The lower photo shows the modified sky which seamlessly blends into the unmodified lower sky by the horizon line because the adjustment to it fades out very slowly, transitionally. Experiment with transitional masks and vary the parameters mentioned here to see for yourself the endless abilities of this form of selection. Next month we'll take a look at combatting flash fall-off with transitional masking.

See last month's Photoshop Tips

IN MEMORY OF CARL VOLK
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>>>>Carl N. Volk<<<< April 8, 1953 - September 5, 2000 Carl's art, talents and teachings will live on for all of us to enjoy.
Visit: http://www.carlvolk.com (Starting Friday, October 27)