1 The Eye is a more powerful camera
Cameras do not have the power of a human eye; therefore, it does not show a person's real and original look. As per a study, it has been observed that a human eye is equal to the 576-megapixel camera.
2 Lighting, shadows & depth of field
When you look from your bare eyes or in the mirror, you appear different, but in the videos, you look distinctive. The reason behind it is that in videos or photos, various elements alter your looks such as lighting, shadows, and depth of field.
3 Characteristics of the monitor's screen
If you use a webcam on your desktop, then your looks might vary as per the properties of the monitor and webcam. Various other factors that might affect are contrast, hue, brightness, and saturation all these elements can make you look different in the videos.
4 The camera angle can change your looks
The camera’s angle plays a significant role in how you appear in the videos. If you think that you do not look great in videos, then you should play with the camera angles as it might make you look better. (See Why do some people hate to appear in pictures?)
5 Video Resolution is usually lower
If you take a video from a regular mobile phone, then its resolution might be disparate or lower than the picture's resolution. Because of this reason, the image might appear ugly in videos when you compare it to the usual images.
6 You see yourself from unfamiliar angels
Well, this reason is more perception-based, as we are in the habit of looking at ourselves from some particular angels. In the videos, the angels change, and we start thinking that we are looking ugly or less attractive.
7 Your picture is reversed
When you look at yourself in the mirror, it is entirely different from the one in videos as the mirror reverses our photographs. However, when you see yourself in the video, it is the unreserved version, and because of that, you might feel that you are not looking beautiful or you look entirely different as you usually look. (See Why do we like familiarity?)