Network engineer [Mario Giambanco] recently purchased a cable to move his flash off camera. Unfortunately, it ended up way too short for his purposes. Instead of purchasing a slightly longer proprietary cable, he decided to employ what he had around him: a lot of cat5e cable and ethernet jacks. He cut the cable close to the center in case things didn’t work out and he’d need to repair it. His post on building the custom ethernet flash extension cable goes into heavy detail to make sure you get it right the first time. He’s tested it using both five and 50 foot pieces of cable with no apparent lag.