Dear Guy, 
   we fully agree, I may have explained myself not correctly. I was just 
mentioning that time-gating with a few time windows is slightly less photon 
efficient, but can provide faster acquisition times. It provide less information 
content per counted photons, but can count a higher number of photons.

It is a couple of years that B&H claims thay can detect lifetimes that fast, but 
I guess this can happen only with their multi-detector system and I personally 
never met anybody that got a TCSPC (good) image in a few seconds.

Cheers, 

Alessandro