The red sensor generally means that it is a TTL-flash dedicated to a certain camera brand. It should say it on there somewhere. In any case, it is not going to work with the Minolta 5D in auto function. You would need to use manual, which is definitely a pain for sports. Try the other flash and see how the auto thyristor works. It's pretty neat once you figure it out. Works as well as TTL. The only trouble I have with my Sunpak 433D is that a) one has to guess and and play around with the settings to get fill-in flash exposure right, b) the auto thyristor is thrown off when I attach the Stofen diffuser and I have to control exposure manually to get it right. Otherwise it works like a charm as direct and bounce flash.