The role of the visor in the camera


2023-02-15 14:35

1. Blurred background

In addition to changing the shutter speed, the    visor can also change the depth of field.

Depth of field: There is a certain length of space in front of the lens (before and after the focus adjustment). When the subject is located in this space, the image on the negative film is exactly between the two circles of confusion before and after the focus. The length of the space where the subject is located is called the depth of field. In other words, the image blur of the subject in this space is within the limit of the permissible circle of confusion, and the length of this space is the depth of field.

To put it simply, the shallower the depth of field, the more obvious the background blur, and the deeper the depth of field, the clearer the background.

Under the same focal length, the larger the shading circle, the smaller the F value, the more obvious the blur effect of the background and the shallower the depth of field. Therefore, if you want to use the camera to take photos with obvious background blur, you should try to use a large aperture under the same focal length.

2, change the shutter speed

Generally speaking, the exposure of the camera at the same sensitivity is determined by the size of the visor (aperture F value) and the shutter speed. In the previous article, we know that the visor F value = the focal length of the lens / the diameter of the lens aperture, that is to say, the smaller the aperture F value, the larger the aperture, and the greater the amount of light. So we can increase the aperture to increase the shutter speed, or reduce the aperture to reduce the shutter speed.

Large aperture lenses usually perform well in low-light environments. In the field of SLR cameras, a series of lenses called "night glasses", such as Nikon Noct58mm/F1.2 and Leica's NOCTILUX-M50mm/F0 The .95ASPH night lens has a large aperture.