Flash F28RM flash, TTL mode, adjust flash compensation, why hasn't the photo changed?

TTL mode of flash control mode is a metering mode, which uses the actual amount of light passing through the lens to determine the corresponding flash output. TTL is the abbreviation of (ThroughHelen), which can be translated as "light passes through the lens". In fact, this metering determines the output of the flash in the field of view seen by the viewfinder, and the probability of failure is extremely low. Historically, the development of TTL is divided into two stages: the built-in TTL metering component of the camera and the flash with TTL function. Interestingly, almost 15 years after the release of the built-in TTL in the camera, the TTL flash appeared. The appearance of TTL brings the greatest convenience to users, that is, even when shooting in a hurry, it is too late to estimate the distance and adjust the aperture, and there will be no big deviation when using the flash, which makes news photography and other work more convenient.