i can get a caustics projection with a point light (though it is very dim - exposure is set to default):

but when i switch to Spot, i get this - basically nothing:

Jonathan, is there any chance you could post your blend file for the finished Spot caustics scene? this is taking me forever and it is just not working, which is a great pity because i really like the technique. 

thanks, julian 

around 4:20 JL switches to Spot light. when i try this i get the following:

as usual, i have tried to copy all the parameters i can see. 

in the video (Using Light Textures, Cookies, and Gobos), jonathan's orb is clearly white, but mine only shows up grey. i have tried to imitate all the settings i can see and think of, but grey is all i get. here is a screenshot:

thx, julian