IR AR Coatings Article from Lifepixel

Here’s an article I found interesting on the Lifepixel site concerning AR coatings and spots occurring on IR images:

https://www.lifepixel.com/photography-news/truth-ar-coated-infrared-filters

And another article to go with it regarding lenses:

https://www.lifepixel.com/lens-considerations/lens-hot-spot-testing-database

Joe

One thing you will see from the data that experienced IR photographers already know - to avoid hot spots or minimize their effect, always shoot with the largest aperture you can.  I try to shoot IR stopped down just one stop from wide open and then focus bracket if I need to.  In cases where I have to stop down more and there is a hot spot, creating LCC profiles for the lens/sensor combo at the various apertures and then applying them in post can often completely correct the problem.

The fact that the AR coatings resulted in some light loss should not be a mystery.  Every coating has some amount of transmission loss.  Often these coatings are designed for visible light so the loss in in the IR wavelengths could be much greater.