jrdoner:
As I understand it, Neopixels are individually loaded with their RGB configuration, then all turned on. I recall reading that they operate with a 400kb/sec. data stream.
The Adafruit NeoPixel library takes care of setting up and sending out the data stream. NeoPixels are based on WorldSemi WS2811, WS2812, or WS2812B. All of them operate on the 800kHz mode unless you are using the discrete WS2811 chip. I was able to run a strip from a wire 8 ft long from my Arduino to the first pixel with no problems. I have spaced them out by a foot between them also with no problem. You do need a filter capacitor on the power supply to help with noise. If you go to the Adafruit site, they have an Uber Guide to NeoPixels that might help you.
jrdoner:
So suppose that I want to set groups of three Neopixels under separated lenses, with a total of six lenses about 4 feet apart. Can any expert out there tell me if such an arrangement would work? If not, is there any way to slow down the data rate to the neopixel strand?
As far as transmission lag time due to distance of wire, the distances you gave there would be a negligible effect. If you want a delay between the groups you can control that through your software. For example you could light the first group. Wait for a 100 microseconds then light the next group, etc.
I would suggest using the StrandTest sketch with the NeoPixel library and try it out.
A few pixels may work just fine with no problems. If you want 3 pixels under each lens, then that would be 18 pixles with 4ft between each lens so 20ft total from the first pixel to the last? You might have a power drop at the end. Are you going to use a power supply, or batteries?
I have done several projects with different types of NeoPixels (WS2811, WS2812B). Do you know which type you have? Are they the in the SMD 5050 package, or 4 pin LED 5mm type, or the modules with an RGB LED with the chip on the board, or the LED strip type?
The bottom line is, without more details no one can give you any definite answer.
We are here to help. And we can only help when we have enough information on your concept to give you specific answers.
I hope that helps!