Material filter - post processing frame

I’m trying to create a material that is transparent but makes everything behind it black and white.
I believe I have to get the current pixel value and then equalize the three channels to make the pixel grey.
What I have come up with so far is this:

but it’s not quite what I want. The square is a MaterialBillboardComponent with the M_Black_and_White material placed under the CameraComponent in the Character blueprint, so it always follows the view. It desaturates everything behind the billboard alright, but it’s too bright. The brightness should be equal to the original colors brightness.

How does Scene Color work? It looks to me like it gets the color information but without effects like bloom etc. If I look up to the sun the bloom is not shown in the square.

You could use CheapContrast(.15 - .2 should be enough) after desaturation.

Hey. You know what? I haven’t really had the opportunity to test this out. But thanks for taking the time to comment.

I’m going to mark this resolved, and open a new one later if need be.

For anyone trying to accomplish this, the OP was on the right track. I used his method and used 1.0 as the value and it worked great. Cheap Contract didn’t work with all of my other materials.