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PHOTOSHOP CLIPPING PATHS

I had a question this month about how to isolate parts of one image in Photoshop so that underlying images and text can show through.

Say you may need a close-up portrait with the background removed, and this needs to be placed over a new background image. Done usually, the upper portrait image would have a rectangular or square bounding box, and couldn't have an irregular shaped outline. If the upper portrait was isolated in say Photoshop then saved, as soon as it's saved the irregular outline is lost, and the image again becomes surrounded by it's own bounding box. So the portrait would have a white bounding background up to its edge, which would cover the underlying image too.

The answer to this is to use 'Clipping Paths', a form of masking or stencilling where you can draw an outline around your image where you want it to be visible, the remaining areas become transparent. The only drawback to this is that the 'stencil' or 'mask' has hard edges, you cannot have a 'fading' or gradual mask as you can with a Photoshop layer. It behaves in the same way as if you had physically cut up a photograph and removed a foreground image from its background. As with scissors, images masked with clipping paths have hard edges, there's no feathering available.

For many images this is no problem, e.g. a car image would have a solid outline anyway so a hard edged clipping path would not be as noticeable, however a portrait of someone with soft curly hair makes it trickier, a clipping path could give them the appearance of having a different hairstyle!


TO CREATE CLIPPING PATHS:

To create clipping paths, you need to draw around the area of the image you need using the 'paths' tool or create a path from a selection, in Photoshop. To create the path for an image, use the Photoshop paths palette various path tools to draw an outline around the image, and that path will finally act as a mask or stencil. You can manipulate and create the paths exactly as required, as the paths act like 'rubber bands' that you can stretch, shrink, shape and bend etc.

Then name and save the path by double clicking on it's layer in the paths palette, then from the paths palette menu use Clipping Paths, and select the path you'd just created. You'll be prompted for a 'device flatness in pixels' - this is how accurate the path is followed by your printer, for normal desktop output enter 1 to 3, for printing press output enter around 6 to 8.

Once you have created the clipping path, you must save the file as an EPS file. Clipping paths generally only work with EPS files, although some packages can handle TIFF's with clipping paths (PageMaker 6.5), the universal standard is for EPS's.

When the EPS is imported into a page layout program, any areas out of the clipping path will be clear or invisible, and the underlying page will show through. Note that in QuarkXPress, for the background to show through, its background must be set to 'none'.

Also note that EPS's use a 'screen preview' low resolution image to represent the image on screen. When printing, the actual high resolution image data is used, so they'll often print far better than they appear on screen. (Sometimes EPS's may have even been saved with a B/W low res. preview that looks absolutely awful on screen, but will print fine!)


PITFALLS TO AVOID:

There is one pitfall to avoid with clipping paths. You can create a path by converting any of the 'usual' masks or selections in Photoshop, however if you use, say the magic wand tool, to create a selection, convert this to a path, then convert this to a clipping path, the path can be rather jagged and can take a while to print. This is because the path uses 'nodes' to control direction and curves--the nodes are the points on the path that can be manipulated to change the path shape by dragging their 'handles'. However, the greater the number of nodes there are in the path, the greater the printing time, and if there are too many nodes the image may not print at all. A path should be relatively smooth-- if it's very 'dotted' with many nodes, one after the other, it may be that you have too many.

As mentioned earlier, clipping paths have hard edges, you cannot have a soft fading edge. If a soft blend between two or more images is required, it may be more appropriate to create a single composite image in Photoshop, using as many layers as necessary. There images could blend from one to another, masks and images can be cut out and edges can have a soft edge as required. Once ready the multi-layered image can be saved as a single 'flattened' or composite image that can be imported into the page layout program, instead of several clipping path images.

It's really down to which is most appropriate for the image you're creating. Multiple blending layers suggest a composite image, a single hard edged image over text or coloured background may suggest a clipping path image.

If you have any DTP or graphic design questions, please feel free to email me at Andrew.Davidson@onyx.octacon.co.uk

Contact: Andrew.Davidson@onyx.octacon.co.uk Until next month, happy DTP'ing. --Andy.





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