Sharper/Softer Shadows

Is it possible to adjust the way light cast shadows in Cycles (make shadows of a specific light source softer or sharper without changing the size)?

I know that adjusting the size will makes shadows softer or sharper; However, I would like to keep my lighting as is and fake how the shadow of a light source is presented. In my case, I am not looking for realistic shadows.

Here is an example where shadows are easily controlled in Maya through “Depth map shadow attribute”

skip to 4:56 https://www.youtube.com/watch?v=9nDAS7IeBgs

I have looked some answers like this: http://blender.stackexchange.com/questions/8930/how-can-i-cast-artificially-darker-shadows
One of the solutions was to “add a light that is only visible to the shadow path, so it won’t add any light, but it will cast shadows”, This could work in my case, but I am not sure how to make the light invisible and cast shadow only?