I have purchased the LED ribbons now, through a supplier on Alibaba. About 7 dollars per meter for LED's that are 21-22 lumens 6000-6500K, Epistar (Taiwan) branded #5050 chips, (1000 lumens per meter at 60 LED per meter). About 35 dollar per reel of high-brightness neutral-color CRI 70-75 LED's. They are perfectly adequate for my needs at a reasonable brightness-versus-cost ratio. They are only CRI 70-75 but this is acceptable. The switching time is sufficiently fast (LED phosphor decay is short -- far less than 1 millisecond). The cost was a bit higher than I hoped to pay, but I need an ultrathin light source (a big panel that's less than 2" thick) that can switch on/off at strobe speed levels, with precision strobe length control. And, if I overvolt carefully, I can get at least 3000 lumens per meter (60 lumens per LED) in short strobes -- since LED's can be overdriven if strobed for really short periods. So I can output over 50,000 lumens from a two-square-foot ultrathin strobe panel, with better and easier control than xenon strobes -- I need to do 120 precisely-controlled full-brightness strobes per second. An 800 watt PC power supply will be supplying the 12 volts necessary for the 250 watt surges of light (more, if I use an overvolted surge circuit). Here's a small section of the LED ribbon, I took pictures of:
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A simple Arduino Photodiode test showed that phosphor decay (after turning off) is undetectable without an oscilloscope -- far less than 1 millisecond. So they are satisfactory in high speed light switching capabilities for low cost! Fiour prebuilt MOSFET switches is what I'm getting (at four channels each), with separate channels controlling a few sections of ribbons, since I need 16-section strobe control.