Quick Clean Composite Images in Adobe Photoshop
Quick Clean Composite Images in Adobe Photoshop

Quick Clean Composite Images in Photoshop

by Kurt Murphy, Paws For Effect, Amherst, NY, USA

©2001 Kurt Murphy. All Rights Reserved. Used at CreativeCow.net by kind permission of the author.

Kurt Murphy Article Focus:
Noted broadcast designer Kurt Murphy explores some basic compositing and image enhancement techniques using Adobe Photoshop. He focuses on ways to avoid the obvious "paste up" look of a shoddy compositing cut-job. He also points readers to some of the productivity short-cuts that will enable you to create your images in the shortest amount of time possible.

One of the biggest challenges facing News Graphic Drones is cranking out an impossible number of stills for a particular newscast. This can be a daunting task, especially when you only have a few minutes per graphic and with The Director In Charge of Still-Stores breathing down your neck. Isolating an image or person to place over your news background can be the most time consuming task, particularly when you’re trying to maintain a realistic look. Nothing looks worse than seeing an obvious cut-job over one of your anchors shoulders.

If you still haven’t purchased a Wacom or other digitizing tablet, do it now (we’ll wait). The Wacom tablet is not a luxury afforded only by the truly nerdy; it’s a must have for anyone who spends a large portion of their day shuffling pixels around in Photoshop. It offers the absolute fastest way to isolate an image. It takes a little getting used to, but in no time becomes second nature... you’ll thank me later.

In this lesson we’ll quickly isolate the two boys (fig. 1) and place them over a new background.

Figure 1

The pen tool is ideal for smooth curves such as automobiles and human shapes, but given the slightly rough line of the clothing I decided not to use it in this case. I chose instead to just erase the unwanted areas with the Wacom pen. I set the Erase tool to either the Paintbrush (at 100%) or the Airbrush (at 50%), both seem work well (I have yet to find a use for the Block eraser).

Before I begin erasing, I duplicate the background layer and then turn it off (poke the eye) leaving the new layer on (fig. 2).

Figure 2

The reason for this is twofold: Now I can erase to the transparent background (checkerboard), and the original file still exists in case I make a mistake (fat chance). Before I start to erase (or draw, or anything for that matter) I make sure that the document is enlarged to a number divisible by 100. Due to the way that the pixels are interpolated, the image is more accurate at 200% than say, 216% (simply press the command - or + one time to get to the nearest hundred). I usually erase at a minimum of a 200% zoom.

I select a hard-edged pen for erasing the background around the clothes, and begin erasing. This task is easily completed by zooming further into the document and using a smaller brush to erase all the tiny nooks and crannies (fig. 3).

Figure 3

I never click on the magnifying glass from the Toolbox (and frankly don’t think it’s worth the pixels that it’s illuminated on). Instead it’s much quicker using the Command + (plus) and - (minus) keys or pressing the Command-Spacebar to access the Zoom Tool (which works no matter which tool you’re using at the time), and marquee the area that you wish to work with. While the document is enlarged, the easiest way to move about image is to press the Spacebar (still with any tool selected) which accesses the Hand Tool. With Hand Tool you can quickly move around the enlarged image.

I erase most of this image in this manner until I get to the hair. Hair is usually the most challenging portion of an image to isolate due to its wispy flowing nature. Many times the easiest way to isolate a desired area is hidden right inside the document itself. With an RGB document, Photoshop gives you 3 shots at isolating a decent, contrasting selection (the red, green or blue channel) in which to use as an alpha channel. A quick check of each channel (Command-1, 2 and 3) reveals that there’s a pretty good candidate for just this case nestled within the green channel (fig. 4).

Figure 4

I drag this channel to the new channel icon to create an alpha channel. Make sure that you do copy the channel to a new channel; by accidentally working directly on an actual red, green or blue channel, you’ll alter the RGB forever and worlds may collide.

Depending upon the contrast of the channel, you’ll probably have to adjust the Levels slightly as was the case here (fig. 5).

Figure 5

Be careful not to adjust them too much, obliterating needed information. Also, depending upon how wispy you wish to keep the hair, you may want to keep the edges a light gray, making them slightly transparent when you place it into a new document.

I invert the image (Command-I) and adjust Levels a little further. Light grays over white are much easier to detect than dark grays over black; in many instances a dark gray simply looks black. My goal is to try to get a pure white area outside the selected area in which to use as my selection (fig. 6).

Figure 6

I sometimes carefully paint or airbrush around the area to achieve this goal. Now the alpha channel is ready to be used to isolate the hair. I load the alpha into my RGB channel and turn off the “marching ants” (Command-H) so that I can see the area better. Using the Erase tool set to a soft-brush Airbrush, I softly “paint” away the background. If the outside area wasn’t pure white, some of the background would still show through.

After the selected image has been erased from the unwanted background area, I use the Lasso tool to circle the selection; Inverse the selection (Command-Shift-I), and then Delete (fig. 7). This is faster and more complete than trying to erase the rest of the document by hand.

Figure 7

Now I have an isolated image of the two boys; I just need to fine-tune it. To do this I make a new Layer underneath the current layer and fill it with white (Option-Delete with white as the main color). This helps reveal any edges that need a little work or any additional spots that need to be erased (fig. 8). Also, by Inverting the image entirely (Command-I) you can see some additional areas that were missed.

Figure 8

The edges around the hair picked up some of the background color and must be fixed. To do this I click the “Preserve transparency” checkbox in the Layers palette and grab the Airbrush again. I press the Option key (to select the Eyedropper), and sample the hair color, then with a pressure of about 7%, I lightly airbrush the unwanted color away (fig. 9). Sometimes you can airbrush at 100% in the Color mode to accomplish this. Occasionally a slight blurring on the edges is needed to soften the area. This can be done with the Blur tool on the alpha channel itself or on the RGB channel after the selection has been cut out.

Figure 9

When I’m finished I toss the alpha channel, the white layer and the original background, keeping only the cut-out layer. Believe it or not, after doing this a few times, this whole process only takes a couple of minutes to accomplish; and your anchors will be very proud to have it resting above their shoulder (fig.10).

© Kurt Murphy • Image courtesy of Photodisc, Inc.

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