I recently bought an IR 760 filter and notice it's almost black, allowing little or no visible wavelengths to pass. Compared to the IR 720 filter I have of the same brand, the comparison is quite stark. I have had excellent results with the 720, rating Rollei 400 IR rollfilm at ASA 6 and developing in D76 for 6 min, but am looking for suggestions for a starting point with the 760. Just as a rough guess I'd say ASA 3 for 400 ASA film as a starting point; it all depends I guess on how much visible is transmitted.

Just as an aside, I found these filters, Green.L from China on eBay and decided to give them a try. They seem to have a narrow product range and make filters for photography and scientific applications, apparently. They claim to use optical glass and high grade aluminium. I now have several of their products, IR and ND, and am impressed with the quality. https://translate.google.com/transla...m/&prev=search The eBay shop is called Galacticos.

Thanks for any ideas.