As they made some note of, Core Animation is very picky about the image format you provide via the contents property. For example, if you retain a reference to

As they made some note of, Core Animation is very picky about the image format you provide via the contents property. For example, if you retain a reference to a CGImageRef that you also assign to a CALayer's contents property, you will end up with at least double the memory usage if it's not in CA's preferred format and it makes a copy of it. In my experience doing that alone can help performance immensely. I've since lost track of the Apple documentation that said it, but CA prefers 16-byte alignment and (kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little) for the pixel format.