I have a UIView / CALayer which I would like to darken. How can I as fast as possible darken it? Is there any way to avoid blending?

Following alternatives is known to me

* create a non-opaque CALayer and set background color and opacity and add it as a sublayer above main layer
* same as above using UIView (can be a tad slower...?)
* render view/layer to UIImage and doing drawing with CoreGraphics (is way too slow and content is dynamic/changing)