I tried out the 540ez lens with both the LED that came with the assembly as well as the LED I bought from digikey. The digikey LED was brighter then the led that came with the 540ez lens. Brightness was judged with the LED installed in the housing, and the projected pattern was the object of judgment.

However, when it came to what the camera saw, it was a different story. At 40ft (the length of my basement; can’t go any longer indoors) the camera was pointed at a blank wall, and all the lights were turned off. The LED that came with the 540ez lens assembly was able to get a focus confirmation out of my 40D whereas installing the Digikey LED in the same lens assembly, did not provide AF confirmation. This was very interesting because the same contrast producing pattern was projected, and even though to the human eye (my eye) the digikey LED seemed brighter, the camera saw something else. At 40ft, I was could not visually  see the pattern projected by the 540ez led (yet focus was confirmed by the camera). With the Digikey LED, I could see the projected pattern (just barely) but the camera was not able to use that information to focus.

The Digikey LED is of 66onm wavelength. I can only guess that the led that came with the 540ez flash is higher then that (nearer to infrared).

I also tested a few other flashes to see if I could achieve AF confirmation on the same blank wall in total darkness, 40ft away.

Canon 420ex – AF confirmation achieved (pattern just visible 40ft away)
Nissin Di622 mark II – AF confirmation achieved (pattern not visible 40ft away)
Younguo ST-E2 – AF confirmation achieved (pattern clearly visible 40ft away)

Looking at the flash quoted AF assist distance I compiled for a few flashes seems to be understated?

The Plan:

Near-infrared is starts at 780nm and goes up from there. So I’ll have to find some LEDs that are between high 600nm and 800nm
OR
Find some brighter deep red LEDs.

UPDATE:

For the next version of the autofocus tool I’m currently working on I need to test several wavelengths of IR light .
3 x IR LED 770nm (p/n: 15P2280)
3 x IR LED 830nm (p/n: 93K0966)
3 x IR LED 850nm (p/n: 97M1058)