Understand ISO sensitivity in photography

Understand ISO sensitivity in photography

When you pick up the camera. Whether you are an amateur or a professional photographer, whether you use film or a digital camera, it is inevitable to deal with the sensitivity. When the camera can't get enough light, you can improve the sensitivity (or use high-sensitivity film).

All photographers rely on light, and light will have different situations in different environments (time and place). It enables photographers to cope with the sensitivity of different light environments, so it has become a very important tool.

For each photo, the sensitivity will affect the shutter speed and aperture selection. When there is little available light, such as in the rain forest, corner or moonlight, sensitivity may be the only hope to take wonderful photos without a tripod. This is one of the reasons why digital cameras make it easier for photographers to use.

Sensitivity refers to the sensitivity of the sensor to light.

According to the ISO value of sensitivity, we can know the sensitivity of film or sensor to light. Compared with ISO 200, the sensor of ISO 100 needs twice as much light to reach the same exposure level.

In order to obtain twice the light quantity, it is necessary to reduce the shutter speed by half (for example, from 1/60s to 1/30s) or increase the aperture by 1 level (for example, from f/5.6 to f/4).

It is obviously not a good idea to slow down the shutter speed, which will increase the risk of blurred photos. So why can't we always use the highest sensitivity setting?

High sensitivity will produce more noise.

The problem of improving sensitivity is that it will produce more noise, but in film photography, this is called? Particles? Sometimes I think I can add photos? Feeling? .

It's not just noise

Noise is not the only problem caused by high sensation. In fact, a * * * will have three problems: noise increases, sharpness decreases and contrast decreases.

Compared with noise, the latter two problems are usually less obvious. Increasing noise will reduce the clarity of the picture and lose details. Lowering the contrast will affect the detail resolution of highlights and shadows.

Noise is always negative?

People spend a lot of time studying the difference between low-sensitivity photos and high-sensitivity photos. It's hard to say which is more suitable. Some noise is not always a bad thing, it may make photos feel more.

Different cameras have different noise levels.

When testing the high sensitivity of the camera, do you feel that the photos seem to be noisy?

Yes, different cameras have different abilities to deal with noise, and the high sensitivity level of cameras has also developed greatly in recent years. If you use a portable digital camera, the noise level of ISO 400 may be similar to other cameras of ISO 3200. And if you use the latest digital SLR camera, it can even be bought over ISO 800.

Now we can enlarge the photo to the maximum size on the screen to check it. But don't forget to evaluate the noise level at the actual size of the photo. Honestly, how many times do you have to use photos larger than A4?

What is the maximum sensitivity that my camera can tolerate?

Take a group of photos with a camera at different sensitivity settings, and check the noise level at common sizes to determine the maximum sensitivity that the camera can tolerate.

Effect of low sensitivity

In some cases, small sensitivity must be used. Here are three examples:

1. You need to shoot running water at a shutter speed lower than 1/2s. At this time, the minimum sensitivity is needed. If the minimum aperture can't meet the demand, you need to use a medium gray mirror.

2. In sunny outdoor, you need to use a large aperture (such as f/2.8) to get a shallow depth of field effect. The shutter speed of most cameras should not exceed 1/4000s or 1/8000s. Try setting the sensitivity to ISO 100 or 50. If you can't meet the needs, you need to use a medium gray mirror.

3. When using the flash. Even with the minimum output, the brightness of the flash is considerable. Use the lowest sensitivity. If the photo is underexposed, increase the flash output.

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