Can Canon 70-200 F4 USM take portraits on cloudy days with flash?

Using telephoto requires a relatively high shutter speed, and hand jitter will blur the picture. Usually, the shutter value reaches the reciprocal of the focal length. For example, when the 200mm end is used, the shutter speed reaches 1/200, and the jitter is basically negligible. This value is called "safety shutter". When using telephoto to shoot portraits, the main function of flash is not to illuminate the picture and improve the shutter speed, but only to serve people's faces. If you want the photo not to be blurred because of jitter, you must first reach the safety shutter. But sometimes the light is not good enough, and the picture quality is poor when ISO is opened. At this time, if there is no tripod, it depends on the photographer's iron hand. When the shutter speed can't reach the safe shutter speed, the correct shooting posture and skills can improve the success rate of getting clear photos. You have to hold the camera in one hand and the lens in the other, and put your elbows together and stick them on your ribs, so as to stabilize the camera. When shooting, hold your breath when you press the shutter for focus, and press it gently to reduce camera shake caused by pressing the shutter. In addition, when shooting, we should make more use of the surrounding environment, such as leaning the camera against a tree or a wall and other fixed objects, which can also make the camera more stable and reduce jitter. Practice more, and the iron hand will be refined to the ninth level, and it will be fine.