When creating photorealistic collages, you need to make sure that the objects that you bring from different photographs will blend together in a plausible way. If you study a photograph in detail (zoom in at 100% and more on a high resolution photograph), you will notice that objects don’t have sharp edges, but they borrow some of the colors from the background they sit against. This is called “spill”.

This is a 300% close-up on an image that I found at sxc.hu.

When you cut an object in Photoshop using, say, the lasso tool or the pen tool (or even the magic wand), you end up with sharp edges, which will make the object look out of place when set against the new background. I cut out my poppy flower and set it up agains a sky also from sxc.hu.

At 300%, here’s how the edges look:

So what’s to do to make it blend better? For your convenience, I have placed in the Ardis download gallery an action called “Cutout Blending”, which you can download for free. Load this action into Photoshop and run it on your sharp-edged object (placed on its own layer).
Note: if you’re working on a low resolution file, use the low-res action, otherwise use the high-res.

What the action practically does is it selects the edges of your object and applies a small amount of Gaussian blur.

Of course, blending the edges is just one small (but very important) step in the blending process. For objects from different photographs to blend well together you should always pay attention to the light direction, the color temperature, the vanishing point, the shadows, etc. But about these we will talk in a future tutorial.

Tags: actions, blending, cutting, photoshop

This entry was posted on Friday, July 25th, 2008 at 12:17 pm and is filed under Graphic Design. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.