What does it mean to enlarge or increase the big picture in digital photography?

Digital photographic magnification or isochromatic magnification means that the image on the film or the holosensor is larger than the main body. Generally, the maximum imaging of macro lens on film or full SLR is 1: 1.

Magnification: The magnification of the lens refers to the ratio of the size of the object projected onto the film (or photosensitive element) by the lens to the actual size of the object. For example, double magnification means that the lens can fill the film with a 36mm*24mm object image (135 camera).

If the field of view of the viewfinder does not reach 100%, the range seen through the viewfinder during shooting is the same as the actual imaging range; If it does not reach 100%, the actual shooting range is larger than that seen through the viewfinder. In this way, the composition is just right when taking pictures, but unwanted content will appear around after the photos come out.

The magnification of the lens is:

Refers to the maximum magnification of the lens. Generally speaking, it is the magnification of the maximum focal length and the nearest focal length of the lens. The magnification of the lens refers to the comparison data between the ratio (width or height) of the captured image and the ratio of the camera sensor.

For example, the sensor width of 135 camera is 3.6 cm, and if the maximum value of the captured image is 3.6 cm (the left-right span of the ruler in the image is 3.6 cm), then the magnification of this lens is1; If the largest image taken is 7.2 cm (the left-right span is 7.2 cm), then the magnification of this lens is 0.5.

Above content reference: Baidu Encyclopedia-Lens