TTL gives output based on the reflectivity of the subject...if they are wearing white...less flash, if wearing black....more flash. I do use ttl on my on camera flash, but it is always bounced (with bounce card) and I juggle my flash exposure for the situation right on the back of the camera(fec). However, I usually have an off camera flash at a set distance on manual also...but ttl can work pretty well if you know how to adjust it on the fly....I do use godox flashes.