So I’ve been building charlieplexed displays and haven’t seen a lot of detail on how various LED types perform in display functions, versus acting as indicators or providing lighting. I just finished up my 3rd display using different LEDs and shot video of them together. The video is pretty good, but it doesn’t do justice to how different they really are unfortunately. The camera’s sensor just doesn’t deal with the breadth of exposures as well as a retina does.
Some editorial observations:
Water clear LEDs. They’re readily available and tend to be the cheapest ones to get in quantity off of eBay. They’re exceptionally bright and that tends to be a disadvantage in a display because they’re almost too bright to look at. Yeah, careful resistor selection and PWM modulation can take the edge off, but they’re still very very bright. 3mm water clear LEDs (not shown) are easier on the eyes and kind of nice in a twinkly way, but they’re fiddly to work with since they don’t tend to have nice flat bases like 5mm LEDs do, so getting them all lined up and coplanar is a bit of a pain. I’ve seen really nice things done with them with diffusers in front of the LEDs, though. They also seem to have a bit of a viewing angle issue - if you’re right in front of them they’re pretty clear, but as you get more off axis, the spilled light tends to turn your display into a blur.
Straw hat LEDs. They’re slightly harder to get, and the auction pictures make them look more diffused than they really are, but at least the batch I got are all tight little pinpoints of light. It’s actually a fairly nice look, and you can view them pretty far off angle without losing too much detail. The ones I have are like normal water clear LEDs without quite so much body, but they still have a domed top. I have some of the other straw hat LEDs where the lens is concave instead of convex and their lighting performance is pretty similar. They’re not quite as bright as the water clear LEDs I have, but they’re a different color, so it might just be a base brightness difference. Hard to say with how thin the documentation is on eBay.
Diffused LEDs. I really like these for display purposes. They’re bright enough to be seen in normal room lighting without being so bright that they keep you up at night. I can see them at pretty much any useful angle, too. The only thing I worry about is that they might not be quite bright enough once the display goes into an enclosure, even a clear acrylic enclosure. But I really like the look in displays.
Going forward I figure I’ll go with the diffused LEDs or straw hat LEDs for displays, leaving the water clear LEDs for other purposes.