The IDAS 48 mm (2-Inch) Round Light Pollution Suppression (LPS) Filter w/ SCT Adapter:
Now IDAS has tweaked the LPS-P2 to more optimize for one-shot color and modified DSLRs cameras. Please see the response curve in the images above.
The key concept on the LPS-D1 is to reduce the reddish background cast like HEUIB-II while blocking light pollution as much as it can. Although LPS-P2 is effectively blocking light pollution while retaining good color balance comparing with other brand filters, it was not as good as HEUIB-II at shown at following my test when color camera was used.
The LPS-D1 is the answer.
As the response curve indicates, LPS-D1 loses SII emission line while LPS-P2 didn't. So this is why it's basically intended to be used with one-shot color cameras.