We know that during the actual focusing of the optical lens, when we focus on the plane of the subject with manual focus, we can gently rotate the focus ring left and right, sometimes it will be clear that the image is clear within a certain range. After a certain range is exceeded, the sharpness of the image is reduced. This involves two nouns, depth of field and depth of focus. Now the VIDEO image mainly shares the difference between depth of field and depth of focus.
Before we talk about the depth of field of the VUV, UV and IR grade MgF2 optics, we will revisit the focus and the circle of confusion with everyone. When the focus is that the light parallel to the optical axis is incident on the convex lens, the ideal lens should be that all the light gathers at a point and then spreads in a cone shape. This point of collecting all the light is called the focus.
The circle of confusion is around the focus, the light begins to gather and spread, and the image of the point becomes blurred, forming an enlarged circle. This circle is called a circle of confusion.
So what is the depth of field of the optical lens? The depth of field is that there is a permissible circle around the focus. The distance between the two circles is called the depth of field. That is, before and after the subject (the focus point), the image still has a clear range, that is, the depth of field.
The depth of focus of an optical lens refers to the distance that the focus (focal plane) is allowed to move along the optical axis of the lens while keeping the image relatively clear.
The difference between depth and depth of field of zero order/multiple order/achromatic optical waveplate
1. Different meanings: Depth of field is the length of the object that produces a clear image; depth of focus is the distance that the focal plane of the image can be moved.
2. When the shooting distance decreases, the depth of field decreases and the depth of focus increases. When the shooting distance increases, the depth of field increases and the depth of focus decreases.
3. When the imaging ratio of the scene increases (such as using a telephoto lens, shortening the shooting distance, etc.), the depth of field decreases and the depth of focus increases; when the imaging ratio of the scene decreases (such as using a short-focus lens, increasing the shooting distance) Etc.), the depth of field increases and the depth of focus decreases.
4. When the aperture is reduced, both the depth of field and the depth of focus increase; when the aperture is increased, both the depth of field and the depth of focus decrease.
5. Depth of field and depth of focus are increased when the definition of image sharpness is reduced; both depth of field and depth of focus are reduced when the definition of image clarity is increased.
6. The depth of focus is largely related to the manufacture of the camera; the depth of field is largely related to the reproduction of the subject.
Practical value of depth of focus
Focus on the large aperture before shooting (the VIDEO image engineer introduces this to increase the brightness of the image and reduce the depth of focus, which helps to accurately focus). After the focus is accurate, adjust the aperture to the position required for shooting. on.