When taking pictures, when to use a large aperture and when to use a small aperture?

Operating the camera is a big problem for many novices. Every brand's camera operation is different, and cameras in the digital age have added many complicated settings. So many photography schools or some teachers will let students know the three most important elements of exposure: shutter, aperture and sensitivity. The application of aperture is particularly important, because aperture is related to exposure, depth of field and even imaging effect.

Aperture digital size ≠ Aperture size

People who are new to cameras or photography will always need some time to adapt to the problem of aperture size, because if you simply look at numbers to allocate, you will often think that big numbers are big apertures and small numbers are small apertures. However, the numerical relationship between the aperture size of a camera and its aperture value is just the opposite, which is a problem that many beginners often encounter. In fact, the aperture value is calculated and becomes the f/ value of the aperture that we are used to remembering, so we can know that the aperture is actually enlarged and reduced.

Calculation of aperture size

In the past, adjusting the aperture directly on the lens also tested the photographer's memory.

So how does the aperture value reflect the aperture size? Let me give you a brief explanation.

Lens aperture diameter = lens focal length/lens aperture f value.

Suppose the focal length of the lens is 50mm, and the aperture diameter is 25mm(50mm/2) in the case of f/2. Under the same lens focal length, if the aperture is set to f/4, the aperture diameter is 12.5mm(50mm/4). It can be seen that if the number of apertures is larger, the aperture diameter will be smaller and the amount of light will be less. Therefore, beginners of photography should keep this in mind to avoid underexposure because of choosing the wrong aperture.

Calculation example of 50mm lens

Aperture number and aperture are closely related to the amount of light entering the lens.

Lens aperture diameter = focal length/aperture f value

(aperture f/2.8) 50 mm/f2.8 =17.86 mm.

(aperture f/4) 50 mm/4 =12.5 mm.

In other words, the larger the aperture number, the smaller the aperture and the less light the lens enters.

What are Grade One and Grade Two?

In the past, the aperture of the aperture ring of the old lens was generally adjusted once every level, and some advanced lenses can be adjusted once every half level.

In the past, the aperture of the lens aperture ring was generally adjusted at each level, and some advanced lenses could be adjusted at half level. These lenses have apertures at each level or half level, so photographers can easily know how much to turn up or down by feeling. But now the autofocus lens is adjusted on the camera instead of rotating the aperture ring on the lens, which is also based on the previous concept of aperture. As long as you remember the rules, you won't make mistakes when adjusting.

The whole aperture difference is 1.4 times.

The complete series of aperture values is as follows:

1/ 1.0, 1/ 1.4, 1/2.0, 1/2.8, 1/4.0, 1/5.6, 1/8.0, 1/ 1 1, 1/ 16, 1/22, 1/32, 1/44, 1/64

The gear design of the aperture is that the numerical difference between two adjacent gears is 1.4 times (the square root of 2 is the approximate value of 1.4 14), the diameter of the light-transmitting hole is twice the root number, the area of the light-transmitting hole is twice different, the brightness of imaging on the negative is twice different, and the time required to keep the same exposure is twice different.

As mentioned above, the smaller the aperture f is, the larger the aperture is, and the more light enters per unit time, and the light entering at the upper level is exactly twice that of the lower level. For example, if the aperture is adjusted from F8 to F5.6, the amount of light entering will double. We also say that the aperture is enlarged by one level. The luminous flux of F5.6 is twice that of F8. Similarly, F2 is 16 times the luminous flux of F8. When F8 is adjusted to F2, the aperture is enlarged by four levels. In addition, many digital cameras can adjust the aperture by 1/3.