PFG, Picture Framing God
So if a picture is to be hung in a room with a window in, it would be better to hang it smack opposite the window than at right angles to it, and if the side walls went away from the window at more than 90 degrees, that would be even worse?Robo, the optical coatings from all makers, as far as I know, utilize reflective technology. That means their effectiveness diminishes with the angle of incidence. You can see this phenomenon in ordinary display conditions. As your viewing angle moves away from straight-on perpendicular toward a side angle view, you can see the anti-reflective quality of any anti-reflection glass product (regardless of brand) diminish. At a viewing angle of about 60 degrees, the anti-reflection quality is nearly gone, and the UV filtering capability diminishes, as well.
On the other hand, the separate coating (or additives to adhesives in laminated glass) from all makers, which are dedicated to filtering UV radiation, utilize absorptive technology. That means their effectiveness remains the same at all angles of incidence.
So, if a manufacturer comes up with a reflective coating to block up to 97% of UV radiation, it still would not meet the ISO 18902 standard, which is based on absorptive technology.