SVG opacity and blend effects

[Gimungus]

I am a long-time user of Illustrator but new to svg filters. I am NOT a programmer but have been able to figure a few things out about how these filters behave.
I am trying to create an SVG filter that will allow me to add a dropshadow to an item in illustrator AND set that shadow’s opacity and/or blend effect.
Is this even possible since the dropshadow is created from the object’s alpha component?
If anyone could send me an example of how to do this I’d really appreciate it.

Thanks