How to understand the concepts of ISO, shutter, aperture and exposure?

To put it bluntly, exposure is the brightness of the photo. If one of the three settings is wrong, there may be underexposure or overexposure, that is, the photos taken are too dark or too bright. So before talking about the relationship between the three, we need to know what is normal exposure, underexposure and underexposure.

What are normal exposure, underexposure and overexposure?

As shown in figure 1, the exposure scale in the frame is a sign to measure whether the exposure is normal or not.

As shown in Figure 2:

When the pointer points to "0" in the middle, it means that the exposure is normal and the brightness of the photo taken is appropriate;

When the pointer points to the negative area on the left, it means that the exposure is insufficient and the photos taken are dark;

When the pointer points to the positive area on the right, it means overexposure and the photos taken are brighter.

Therefore, in order to make the exposure normal, aperture, shutter and ISO must cooperate with each other. How do they work together? Then look down.

Second, the relationship between aperture, shutter and ISO

Take the faucet in Figure 3 as an example to illustrate: If you take a normal exposure photo and fill a bucket with water, we use the size of the faucet valve to represent the aperture, the water flow time to represent the shutter, and ISO to represent the filter.

Assuming that ISO remains unchanged, it will take longer to fill a bucket of water if the faucet valve is turned down. If the tap is turned on, the time to fill a bucket of water will be shortened. Therefore, the relationship between aperture and shutter is a dynamic balance.

ISO acts as a filter. The larger the ISO, the larger the gap of the filter, but the more impurities there will be, and the photos taken will have a lot of particle noise. Conversely, the smaller the ISO, the smaller the gap of the filter, the less impurities and the cleaner the photo.

From Figure 3, we can get the following truth:

The faucet is fully open (assuming the aperture is F4 at this time)+2s running time (shutter time) = a bucket of water is filled (normal exposure).

The faucet is half open (assuming the aperture is F5.6 at this time)+4s running time (shutter time) = full bucket of water (normal exposure).

For the same bucket filled with water, two different parameter combinations can be used, as shown in Table 4.

Apply this example to our usual shooting:

If slow shutter operation is needed, such as recording motion trajectory, the aperture can be reduced and the shutter time can be extended;

If you need a large aperture operation, such as blurring the shooting background, you can increase the aperture and shorten the shutter time.

At this point, this tutorial is over. Honey Tea will give you a summary:

① Aperture, shutter and ISO jointly determine the exposure of photos;

② Take a photo in normal exposure, with the ISO unchanged. The larger the aperture, the shorter the shutter time; The smaller the aperture, the longer the shutter time. ?

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