I use a Canon 600D SLR camera with an external flasher for indoor flash shooting. Why is it always overexposed?

If a flasher is used to flash the machine, the flasher should be set to manual mode. If the picture is overexposed, you can try to reduce the flash index of the flash or reduce the ISO of the camera.

From this picture, it seems that vases and petals are clearly visible from the picture you uploaded. . . It may be enlarged to 100%, and the sharpness may not be enough. . . In fact, if you only need to blur the background, you don't need to fully open the aperture. If you receive 2.0, you can blur the background and ensure enough depth of field to focus all the parts you need. In fact, the background of this picture is a white wall, which will not have much influence on the picture. If you want to propose a theme, you can try to change the angle of the flash, make vases and flowers light up and darken the background.

If you must turn to 1.4, the flowers and vases are very clear. You can try to adjust the focal plane so that the camera is slightly tilted, and the distance between the clear flowers and vases and the hammer of the camera is equal.