Sun May 13, 2018 3:57 pm
Many regular ND block visible light but not IR, letting IR take over more and more the stronger the ND is. From what I've read, the Firecrest filters aren't actually IR-blocking filters, what they do is block IR to the same extent as they block visible light. So, if you have an IR problem to begin with, a Firecrest won't fix it, but it won't make the IR problem worse. If you want to block IR completely there's other filters for that, such as Schneider Tru-Cut 680 and Heliopan Digital UV/IR. These are not ND-filters, as they block IR but not visible light. They are great, if not necessary, if you use a lot of tungsten lights.