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 features a great set of parameters, but most professionals will use the lasso tool, 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 stair-stepping. This way the viewer cannot tell which, if any, areas of your image were customized. 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 fade, like a vignette effect, you should feather your seletion 30 to 100 pixels, depending on the resolution of your scan. Don't forget the standard features of the lasso tool: Option Key to "rubberband," Shift Key to add one selection to another, Command Key to subtract from a selected area and Option & Command Keys to move a selection (without moving what is in the selected area). Another way to create a selection is by using Paths and then chane it to a selection then add feathering. Advantages in using Paths for making a selection: 1) If your selection is more geometric and sharply defined, it can be more accurate and quicker to use paths (i.e., a perfect circle or rectangle); and 2) More critical selections are made with paths because of the ability to refine the selection (using directional arrows for minimum movement of points). For pointers on scan resolution, see the "Photoshop File Resolution" article above. For information about scanning and digital imaging devices, read "Getting Digital with Your Images" - see Link to the right.

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SEAMLESS SELECTION

In the photo above (a drum scan from a 4x5 transparency) the river was selected with the Lasso tool with 2 pixels Feathering (at 300 dpi). After adjusting the Levels, the Hue and Saturation of the selected area were changed to create a color slightly bluer than the less-appealing original neutral-brown.

TRANSITIONAL MASKS

The key to editing an area of an image in Photoshop is selecting it properly. If you haven’t read the article below on “Seamless Selection,” you might want to refer to it (left column) before digesting this information on transitional masks. 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 (as I did in the sky in the Photoshop Tips banner image above-left), create a new channel by selecting all (Command A) and Save Selection as a new channel. Go to the new channel, make your foreground color black and your background color white and use the transitional tool (linear mode), 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. Go back to the composite channel (Command 0 for color images) and load the selection channel. The selection marqee 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. Another example of this “burning the top of the image” is the “Desert Tree” photo seen on the Fine Art Photography homepage (see Link below). An example of using a radial transitional mask is the “Digitized Nude” photo on the page that has the article titled, “Getting Digital with Your Images” (see Link below). A radial transition, from black to white, is started at the point in the photo where there appears to be no digital filtration and goes to the far corner (in a separate channel). The selection is loaded and then the filter (in this case the Pixelate-Mosaic filter) is applied creating a digital effect that gets stronger as it moves towards the outer edges of the image. Experiment with transitional masks and vary the parameters mentioned here to see for yourself the endless abilities of this form of selection.

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