I have been seeing a lot of FILT-based contraptions lately and I wanted to know if there was a tutorial like the one for subframe. I don't understand how it works and how to make photons interact with other photons so so help will be greatly appreciated.
AFAIK there's not FILT tutorial yet, but the wiki page (https://powdertoy.co.uk/Wiki/W/Element:FILT.html) explains it well.
Digging through old saves there's some useful information you can learn on less complicated subframe filt circuit/contraption.
How-tos FILT bit value manipulation on Sandwichlizard's save
forthe:
AFAIK there's not FILT tutorial yet, but the wiki page (https://powdertoy.co.uk/Wiki/W/Element:FILT.html) explains it well.
This one is a good start. Essentially on wiki you can see how FILT ctype value determines the wavelegth of FILT and tmp determines the operator of FILT, you get the idea. DTEC also used to transmit/copies filt bit value, and so other sensor element as you can see in Cracker1000's save below.