Found this article by Bret Malley and felt it was helpful when creating composites to know this information.
5 Critical Techniques for Seamless PS Composites
Compositing in Photoshop can be nothing less than pure digital fun—especially when you have the right tools and techniques to use. I personally find compositing addictive, much like a good book or computer game, but with one major difference: Playing in Photoshop, you don’t just come away with a high score or memorable story; instead, you have a tangible and creative accomplishment you can share with the entire world.
Much like when mastering any game or developing a solid skillset with any type of technology, you might be frustrated by not always being able to do what you want or get great results when compositing in Photoshop. The craft of compositing is not easy. However, in this article, I’ll help you to develop skills in the craft by describing my top five compositing strategies—giving you my hard-earned advice for creating imaginative and seamless composites. Learn how to make it fun instead of frustrating!
Make Good Selections and Mask Seamlessly
There are a few key strategies to try when making selections and masking. The first strategy is pretty general: Practice handling the various selection tools and learn how each works. Knowing when to whip out which tool helps with productivity as well as masking times and quality. I get into the nitty-gritty of each selection tool in my book Adobe Master Class: Advanced Compositing in Photoshop, but in short, you can sum up selections as used primarily for helping with masking—leaving out all the parts you don’t want seen, while keeping visible every finger, toe, and even hair strand you want to show. Sometimes (such as when compositing landscape scenery), I’ll even skip the selections part and jump straight into painting organically on a mask.
In case you didn’t know (or just forgot), masking is essentially nondestructive erasing.
Even with seemingly good-looking selections and proper tool use, once you apply a mask to a layer, it might look “off” for unexplained reasons. This is because our eyes know when something isn’t right, even if the brain can’t pinpoint the problem. The main kicker for just about all masking is to match perfectly the masking edge’s sharpness or blurriness against the surrounding imagery. In essence, this is how you can avoid that fake-looking cutout “collage” feeling in a composite. If the masking edge of an object is sharper than the sharpness of the images around it, the composite will look wrong to our eyes. The same principle applies if the masking edges are too blurred compared to the surroundings—sadly, we see this all the time; it’s called bad compositing, or sometimes termed collage art. (Oh, slam!) For seamless compositing, look critically at the edge along the layer you’re masking. If you see a blur of two pixels on the image itself, make sure that the masking has a similar feathering around its edges.
Cleaning Up Edges with Photoshop’s Fantastic Refine Edge Feature
To refine a selection before masking, try the Refine Edge button on the options bar. This feature will let you avoid small “halos” of selected pixels just outside of the intended selected object. The Refine Edge feature lets you adjust a selection’s edge in a number of ways, such as biting into the selection to reduce the potential for halos, and feathering the edge to match the blurriness of the image being selected.
Move the Shift Edge slider to the left to -30% or -40%, so it bites into the selection a little, and add a small amount of feathering to the selection as well (see figure). A setting of about 0.5–1.0 px is a safe place to start using the Feather slider in the same dialog box.
Painting around hair after this dialog box is open will accomplish nothing less than mind-blowing hair selection results in cases of fairly nice contrast. (The Refine Edge feature uses a somewhat hidden tool called Refine Radius, made just for this kind of hair selection.)
Match Lights and Darks Before Matching Colors
Back to that jigsaw metaphor I mentioned earlier: Combining disparate imagery can be quite tricky, to say the least. To help with knitting together two very different shots, start by matching the lights and darks. Changing the lights and darks of an image will invariably change the coloring and everything else in some way, so it’s a good idea to start with a Curves adjustment layer to get the values matching nicely before moving on. (By the way, values is just “art speak” for lights and darks.)
To make an adjustment layer affect only a single layer rather than the entire stack below it, clip the adjustment layer to the layer you want it to affect. Do this by placing the adjustment layer directly above the layer you want to adjust; then hold down Alt or Option and click the line between the two layers. Bam!
Even taking shots with the same general setup can still give you different coloring sometimes, especially when dealing with natural light and a partly cloudy day—working with clouds is simply a pain! Once your lights and darks match up, changing the coloring is often a good idea. There are a zillion different ways to do this (as with nearly everything in Photoshop), but my favorite is to use a fast-and-easy Color Balance adjustment layer. With very little slider movement, this adjustment will let you get things pretty close to perfect a majority of the time.
The other adjustment I often use in tandem with a Curves adjustment layer is a Hue/Saturation adjustment layer. This technique lets you compensate for the increased saturation that often accompanies playing with the lights and darks of an image. Add one of these adjustments, clip it to the same layer as the Curves, and then desaturate with the desaturation slider until the image meshes seamlessly with its surroundings.
NOTE: The article also contained information about photographing and composites.
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