IES Lighting on Transparent Alpha Background I've been looking for this question and answer but have only come across a similar one in regards to shadow, I was unable to find an answer.

I'm creating assets for a project and am using IES lighting for certain light models (These are built into the models as flat planes, if you can imagine transparent textures around the edges of the model with "Bloom" effects)

I use a generator to create different styles of IES and can import them into Blender as lights, but the problem is capturing the lighting itself with a completely transparent background, so the image can be used as an "Overlay" on textures, such as Brick, Stucco, Wood etc. 

I was thinking I could have the light casting the effect on a wall, somehow change the wall and background to be transparent and be exportable with an transparent/alpha layer.

Any ideas on how to do this?
Yes, you can do this with a holdout shader on the diffuse plane:



Note that the world background must be completely black/zero strength so that there are no other sources of light in the scene, and Transparent should be enabled in Render settings > Film.