In photoshop, a path is a vector that you can use to select an area of the content you are working with. It isn’t a raster selection representation, like when you use an opacity mask on a layer (see below).
The black/white opacity mask above represents the selection that the saturation layer is acting upon, and it is actually a black and white “image”, if you will. And that isn’t what a clipping path is.
For the purposes of this discussion, I’m going to reference this recent file of mine on iStockphoto.com:
A clipping path is a vector path, as I mentioned, painstakingly drawn by hand around the object in the content, in this case a pumpkin. I don’t normally provide clipping paths, because most of what I shoot doesn’t lend itself to the process. Clipping paths are good for really hard edged objects, like a brick, or a pumpkin. You cannot provide areas of feathering or opacity along the edges of a path. It is what it is – a curve. It is up to the designer using the curve to then feather and otherwise modify that selection to their uses.
To see a clipping path, in photoshop, open the “Paths” window. If there is a clipping path, it should be there. It will be named whatever the creator named it. The .jpg format holds onto this information just fine.
In Photoshop, if you change to the selection tool, and click on the path, you can see the defining points.
If you right click on the path name, you will get the option to make a selection from the path.
In the next option box, you can modify the selection with several options, and then you have your selection to with as you will.
Here, I’ve made a thoroughly exciting example, by taking the path, and cutting out the pumpkin and putting it on it’s own layer. I then added an orange layer behind it, some text, and then a white stroke around the now cut out pumpkin.
Clipping Paths on iStockphoto
There have been discussions on the forums about whether people should include clipping paths. The impression I get, is that mostly, designers like to make their own selection paths. As I mentioned, clipping paths are good for hard edged things, like blocks and pumpkins, not so good for things like hair, for example.
On iStockphoto in the past, clipping paths, if provided by the creator, were only in the largest file version. The clipping path did not get translated down to the smaller versions when the resize happens. So, if you wanted a clipping path on an image, you need to buy the largest version of the image. Apparently, this has changed recently, as smaller sizes of recent images now appear to have the paths translated. I do not know if this has been applied to earlier images or not.
So, how do you know if the image has a clipping path? The designer will usually note it in the title and/or description – “Pumpkin with Clipping Path”. Also, there is a keytag “clipping path” that you can use in searches, like: “clipping path” pumpkin .
Downloading an image that does not have a path, when you are led to believe it does, is probably good reason to contact support for a refund.
If you’re interested in making your own paths, check out this iStockphoto article on paths.