70-200 portraits, do you want to reduce the aperture by two steps? What aperture does a photo studio usually use?

It is estimated that many people have heard of "Sixteen Sunshine Articles". A few decades ago, at that time, cameras generally did not have metering function. All films are printed with "Sixteen Rules of Sunshine" on the box, which provides you with exposure basis. "Sunny Sixteen" refers to the aperture of F 16,1100 seconds for films with GB 2 1 and ASA 100 (equivalent to ISO 100 today). The only reason why I mentioned "Sunshine Sixteen" again is "Sixteen", which is F 16. I want to explain that in those days, F 16 was a common aperture.

There was a photography club called "F64" in history. They emphasize that the photos must be clear, both far and near, so the commonly used aperture is F64, hence the name.

What is the most commonly used aperture for beginners in DSLR and E-5 10 today? What kind of aperture should I use? Some people use F8 most frequently in statistics, but they have different opinions on why it is F8. Some people even say that F8 equals "Who cares?" .

The numerical value of the aperture is called the aperture coefficient, prefixed with f, and the numerical value is equal to the lens focal length/aperture diameter. For example, a 50mm/F2.0 lens has a maximum aperture diameter of 50mm/2.0, that is, 25 mm When taking pictures with this lens, the aperture diameter of F8 is 50mm/8 and 6.25 mm The aperture has two functions, one is to control the amount of light entering, and the other is that the thickness of the aperture will change the clear range of the scene in the photo, which is the so-called depth of field.

Cameras use apertures and shutters to control exposure. For example, turn on the faucet to fill a basin of water, the aperture is the faucet, the shutter is the time to fill a basin of water, and your washbasin is the image sensor (CCD, CMOS, LMOS). DSLR generally has four exposure modes, such as E-5 10 with M manual, A aperture first, S shutter first and P program.

M means you turn on the tap yourself, the size is up to you, and the time to pick up the water is up to you. Pick up as much as you want, and if you pick less, it will be wasted. A: Turn on the tap yourself and an old lady will watch it for you. When the old lady is full, turn off the main gate. There is an old uncle who wears a watch. You tell him when to come back and take the basin and water away. He will turn on the tap for you and make sure that the water is full when you come back. P is the laziest way. You ask an hourly worker to fetch water for you. She decides how and how long to turn on the tap, and all you get is a basin of water.

These exposure methods have their own advantages and disadvantages. I think beginners should first master the A-aperture priority exposure mode, because the aperture not only controls the amount of light, but also affects the depth of field. Generally speaking, a camera "sees" things with a visual range. Things within this range can be seen clearly, and things beyond this range can't be seen clearly. This clear range is the depth of field.

The factors that affect the range of depth of field include camera specifications (such as 4/3, APS, 35mm Quan Huafu, etc.). ), the selected aperture size, the focal length of the lens, the shooting position, the distance from the focus to the lens, etc. There are several rules:

First, in a fixed shooting position, the same camera with the same specifications and lens focal length is aimed at the target (the focus is fixed on the target). We are used to saying that the smaller the aperture (the smaller the aperture), the larger the range that the camera can see clearly and the greater the depth of field (the deeper). The smaller the F coefficient, the larger the aperture (the larger the aperture), the smaller the clear range and the smaller the depth of field (the shallower). For example, E-5 10 uses a 50F2 lens with a large depth of field F2.8 and a small depth of field F2.

Second, at a fixed shooting position, use the same camera with the same aperture coefficient to focus on the target. The shorter the lens focal length, the greater the depth of field, and the longer the lens focal length, the smaller the depth of field. For example, the E-5 14-42 lens is used for E-5 10, and the same F8 aperture, the depth of field at the end of 14mm is large, and the depth of field at the end of 42mm is small.

3. Focus the target with cameras with the same specifications, lens focal length and aperture coefficient. The farther the shooting position is from the target, the greater the depth of field, and the closer the shooting position is to the target, the smaller the depth of field. For example, E-5 14-42 lens is used on E-5 10. 14mm, F8 aperture, the depth of field is 0.8m ~ 16m away from the target, and it is about 0.6m ~ 2.5m away from the target.

Fourth, still in a fixed shooting position, with the same specifications of the camera, the same lens focal length, the same aperture coefficient, focusing on the scenery at different distances (the focus is not fixed on the target), the depth of field range is different. When the distance from the focus to the lens is equal to "hyperfocal distance", the maximum depth of field (from hyperfocal distance /2 to ∞) can be obtained. For example, E-5 10 uses 14-42 lens. At the end of 14mm, the hyperfocal distance is about 1.6 m, focusing on 1.6 m, and the depth of field is 0.8 m to ∞. Hyperfocal distance is defined as the distance from the nearest point of depth of field when the focal length is ∞. For E-5 10, hyperfocal distance = the square of the focal length of the lens/aperture coefficient/15 (the focal length of the lens is calculated in millimeters and the result is meters).

The depth of field of cameras with different specifications can be converted according to the lens conversion coefficient. Theoretically, it can be proved that the camera of 35mm Quan Huafu (135) is the standard, and the camera of 4/3 (lens conversion coefficient is 2) has the same focal length/lens conversion coefficient, aperture coefficient/lens conversion coefficient, and the blurred degree of the photos taken is the same. For example, a 35mm full-frame camera with a focal length of 50mm and an aperture of F 16 has the same effect on viewing angle, depth of field and blur as a 4/3 camera with a focal length of 25mm and an aperture of F8.

The predecessor of F64 mentioned earlier did not use a 35mm full-frame camera, but a large-format landline. If the film size is calculated by 4 inches by 5 inches, the lens conversion coefficient is about 1/4 based on the 35mm Quan Huafu standard. In order to get the same effect as 35mm Quan Huafu, 50mm and F 16, 200mm lens is needed.

Therefore, four-thirds of the F8 and 35mm full-width "Sunshine Sixteen" and "F64" clubs are essentially the same.

If the depth of field is not considered, what aperture is the best only from the perspective of imaging quality? I often see some brave netizens, and the photos posted are the maximum aperture of the lens, because some digital experts tell them that the maximum aperture of the digital lens is the available aperture. I often see some cautious friends who always close the second or third aperture when filming, because the old-timers in the film era have repeatedly reminded that closing the second or third aperture is the best time for lens imaging.

To understand this problem, you need to know a little about the principle of the camera. For example, E-5 10, when the shutter is pressed, the camera has at least four actions: autofocus, metering, reducing the aperture and opening the shutter. I also have an old Olympus film machine OM- 10. I have to focus manually before pressing the shutter. After pressing the shutter, I will measure the light, narrow the aperture and open the shutter. The problem is focusing. In order to facilitate focusing, the aperture is at the position of the maximum aperture when focusing, and the aperture will receive the preset value after pressing the shutter. Anyone who uses an excessive image screen knows that the maximum aperture of the lens is small, and the image splitting screen is often black and unable to focus. Therefore, for cameras with no autofocus function in the film era, the lens with the maximum aperture F4 is not easy to use. At least F2.8 manufacturers know this very well, so when designing the lens, the maximum aperture is not used for taking pictures at all, but for focusing, so the lens is cheaper. The digital age has changed. It's all autofocus. Whether it is right or not is up to the machine, and the effect of the maximum aperture is clear at a glance. There is no need for manufacturers to produce large-caliber lenses to focus. This is also the reason why F4 lens has become the mainstream in the digital age.

The smaller the aperture, the better. The smaller the aperture, the larger the deflection angle when the light reaches the image sensor, which is more unfavorable to CCD, CMOS and other photosensitive elements wearing convergent glasses. If the aperture is too small and the image field is too dark, the contrast of details will be lost, which is commonly known as sharpness.

If you use a digital autofocus lens, my experience is that you will be satisfied with the effect of receiving 1/3 files. In the film era, it is necessary to reduce the aperture of the second and third gears if you use manual pan/tilt, but considering that the imaging range of the 4/3 system is only a part of the middle of the old lens field, it is almost the same to reduce the aperture of the first and second gears.

If you are not satisfied with your photos, look at the common aperture. If you always use the maximum aperture, change this habit and try 1/3. If some photos use the aperture above F8, you should take a closer look at whether it is really necessary. If your photos are all F 1 1, F 16 or even F22, then you have found a reason why the photos are not ideal.