Poor Man's IR Filter

Back in the day when most folks did black and white photography, the title of this post probably would've made sense. Not so much any more. But just in case you have a stash of Wratten filters lying around, this trick might work for you:

It's crosses 50% cut-on at 770nm, and passes 85% at max transmission. It's not the best IR filter in the world (the Hoya 72R cuts on at 720nm and has better overall transmission.) But if you already have the Wratten filters lying around, it's a freebie. Also, unlike many infrared filters there's no UV leak, so you're getting straight infrared on your detector.

Yes, the infrared picture I took in my previous post was taken with this stack. It really does work!

Tom