When should I use the visor?
The light-shielding ring plays a role of light-shielding, such as the light-shielding ring of the mobile phone lens and the light-shielding ring of the camera lens. It is stamped and formed with SOMA shading material, and a piece of Mylar inlaid in the lens. Because it plays a role in shading, so people call it shading ring, shading gasket.
Its principle is based on the principle of physical phenomenon (small hole imaging), and the processing requirements are relatively strict. Therefore, the requirements for materials also have a higher level of demand. The market basically uses Japanese SOMA shading materials.
When to use the visor:
Prevent glare and improve contrast: The main purpose of the lens hood is to reduce the possibility of lens flare. Lens flare usually appears in the image in the form of colored spots (especially in backlight or side backlight), which is mainly scattered by the lens. /Caused by reflected light. And the hood can also improve the overall contrast and color in the photo.
If you don't want the light spots shown in the picture above to appear in your photos, you'd better use a light-shielding ring. If you are shooting directly at the sun, using a hood will not work, but when the sun (or any light source) is outside the frame, it can indeed prevent halo.
Protect the lens: When you walk around, your camera sometimes bumps into things. The lens hood can protect the lens from damage.
When not to use the visor:
Create halo effect: If you want to create use halo effect, as mentioned above. Please do not use the visor, and tilt the lens to a certain angle to get some glare or fade effect.
When using a pop-up flash: The lens hood sometimes blocks the light from the pop-up flash to the subject and creates a shadow in the middle and lower parts of the image.