What is the relationship between sensitivity and exposure?

Students who are new to photography always have many questions, such as what is the relationship between sensitivity and exposure? To understand the relationship between sensitivity and exposure, we must first understand what sensitivity and exposure are. The following is the relationship between sensitivity and exposure that I have carefully arranged for you. Welcome to refer to!

What is the relationship between sensitivity and exposure?

The relationship between exposure and sensitivity can be imagined as a bucket connected with tap water. Water flows down from the water pipe to the bucket, just like light enters the camera, and exposure is equivalent to this process. Overexposure is when water overflows the bucket, and the exposure is equivalent to the amount of water in the bucket. This is usually determined by the shutter time and aperture size of the camera.

It can be imagined as the time when the faucet is turned on and the size of the water flow. Sensitivity is the sensitivity of film or photosensitive element in camera to light. If the sensitivity is high, that is to say, the film or photosensitive element in the camera is sensitive to the entry of light, then the light can be recorded by the camera more quickly, that is, the bucket can be filled with water more quickly.

How sensitive is it?

Sensitivity is the chemical reaction speed of film to light, and it is also the standard of photosensitive speed in film manufacturing industry.

Sensitivity of film to light; Low sensitivity refers to film (film) below ISO 100, medium sensitivity refers to ISO 200~800, and high sensitivity refers to ISO 800 or above. When using traditional cameras, we can choose negatives with different sensitivities (speeds) according to the brightness of the shooting environment. For example, iso200 can be used in cloudy environments, iso400 or higher can be used in dark environments, such as stage and concert environments, and digital cameras have similar functions. It changes the iso value by changing the amplification factor of the signal amplifier in the photosensitive chip, but when the iso value increases, the amplifier will also amplify the noise in the signal and produce a coarse-grained image.

What's the exposure?

Exposure refers to the integral of the illuminance Ev received by a surface element in time t. ..

The light metric corresponding to the irradiation dose he is the exposure dose Hv, which is defined as the integral of the illuminance Ev received by the surface elements of the object in time t, that is, Hv=∫EvdtHv is measured in lux (lx s). If the illuminance Ev on the bin is independent of time, the above formula can be simplified as Hv=Evt.

A. The higher the sensitivity, the smaller the exposure required; Conversely, the lower the sensitivity, the greater the exposure.

The greater the B.B.ISO value, the higher the sensitivity; Conversely, the smaller the value, the lower the sensitivity.

C the sensitivity is graded according to the exposure of 1/3.

For example, ISO/22o is higher than ISO/2 1o 1/3.

Wan O200/24o and ISO 100/2 1o

The calculation formula of ISO is H S = 0.8 (S sensitivity, H is exposure). As can be seen from the formula, the higher the sensitivity, the lower the requirements for exposure.

Extended data:

Sensitivity, also known as ISO value, is a measure of the sensitivity of negative film to light, which is determined by the measurement of sensitivity and several values, and has recently been standardized by the International Organization for Standardization. For the negative with low sensitivity, it takes a long exposure time to achieve the same imaging effect as the negative with high sensitivity, so it is usually called slow negative. Highly sensitive negatives are therefore called fast negatives.

Whether it is digital or negative photography, in order to reduce the exposure time, the relative use of higher sensitivity usually leads to the decline of image quality (due to thicker negative particles or higher image noise or other factors). Digital cameras can improve ISO by improving the sensitivity of photosensitive devices or merging several adjacent photosensitive points.