Analysis of camera exposure mode

The most common exposure modes are as follows:

Automatic exposure (P file), aperture priority (Av file), shutter priority (Tv file) and manual mode (M file).

If it's a girl, direct P-files, portraits, scenery and sports are enough.

Boys are still a little more demanding, so when talking about these four exposure modes, we should talk about the three elements of exposure: aperture, shutter, ISO and their relationship.

0 1 aperture-aperture takes precedence

Aperture is a device used in the lens to control the light to pass through the lens and enter the photosensitive element in the fuselage.

We use the f value to represent the aperture size.

Aperture f value = lens focal length/lens aperture diameter

The larger the aperture, the more light enters the camera and the more photos are exposed. ?

In aperture priority mode, we can adjust the aperture by dialing the control dial on the camera.

In this mode, the camera will automatically match the shutter and ISO (set to automatic) suitable for the current aperture for you according to the metering results.

Get the most suitable exposure under this aperture.

In what mode do we need to use Av files?

Blurred background-use a large aperture

Starlight effect-small aperture+tripod

Dream point-big aperture+night scene

...

02 shutter-shutter priority

Shutter is a device used to control the exposure time in a camera, and the unit of shutter speed is "seconds".

Common shutter speeds are:11/21/41/811/301/65438+.

The exposure difference between the shutters at each stage is twice.

In addition to the exposure time, the shutter also determines whether the moving object you shoot is blurred.

For high-speed moving objects, we need to shoot with a faster shutter, while for still objects, we can shoot with the lowest shutter higher than the safety shutter to get the best picture quality.

Safety shutter = reciprocal of focal length

For example, when shooting with a focal length of 50mm, the safety shutter is 1/50s, which means that we should choose the shutter time of 1/60s for hand-held shooting.

When the shutter speed is lower than the safety shutter, it is easy to blur even when shooting still objects.

But there are some scenes that we need to shoot with a lower shutter, such as night scenes, light tracks, milk waterfalls, white gauze beaches and so on.

(optical track)

In these scenes, our shutter time is often 2s or 4s, which is lower than the safety shutter.

At this point, we need to use a tripod to keep the camera stable for shooting.

In the shutter priority mode, when we choose the appropriate shutter, the camera will automatically match the most appropriate shutter and ISO (set to automatic) for us according to the photometric results, so as to obtain the most appropriate exposure results.

03 ISO sensitivity

Sensitivity is a numerical value to measure the sensitivity of a camera photosensitive element (CMOS) to light. The higher the sensitivity, the more sensitive the photosensitive elements on CMOS are to light, and the more exposed they are.

The light is weak when shooting at night, so it is necessary to improve the sensitivity to increase the exposure.

However, blindly increasing the sensitivity will reduce the image quality and make the photo appear noise, as shown in the following figure:

The above is a brief introduction to the three elements of exposure. In practical use, it is necessary to choose the appropriate mode according to the specific situation and control the three elements. If we need to control the aperture and shutter at the same time, then we need to use M-range manual mode to control.

In manual mode, the parameters in the camera can be adjusted. How powerful its function is, you need to explore and summarize it in practice.