Allow negative luma min values for the luma key fIlter

[SoftlySteph]

Sometimes I want to apply a luma key and only remove light pixels, but it cuts out pure black by default even when luma min is 0.

TYSM! <3

 

[AaronD]

There's a Luma Max and a Luma Min setting, that seem to define either side of a range of values. What happens if you use the other setting?