RETRA Strobe Thread in Lights, Strobes, and Lighting Technique Posted October 16 · Edited October 16 by Pavel Kolpakov 3 hours ago, Jay-11 said: Pavel, I have one of the original Nauticam TTL converters that I purchased when the D500 housings came out. Will I need to replace that converter with a new one to work reliably with the Retra Pro V2.5 strobes? You mean #26308 product (black color PCB). It did not have Retra TTL profile, no HSS support. Yes, for usage with Retra Pro, you have to replace TTL board.