Learn to adjust the parameters of SLR camera in 7 minutes

When a novice gets a SLR camera, he usually asks, What are so many buttons for? How can I take pictures? Why are photos sometimes dark or too "virtual"? What are camera parameters? What the hell are shutter, aperture, sensitivity, white balance, photometry and focal length?

Don't worry, this article will help you solve it!

First, let's find out what is the reason for adjusting the parameters:

Mainly because of "different lighting conditions"

We adjust the parameters according to the light. Sunny, cloudy, night and indoor light require different parameters. On the other hand, if you shoot different objects in the same light, you usually don't need to adjust the parameters. (There are also special circumstances)

The main purpose of adjusting parameters is:

1. "Take photos with accurate exposure"

2. "Make sure the photos are not blurred by shaking hands."

The first point is easy to understand, that is, neither too bright nor too dark;

The second point is also very important, because if the shutter speed (exposure time) is too long, such as more than 1/5 seconds or even a few seconds, it is difficult to guarantee that the hand will not shake for such a long time, so it will paste.

However, the adjustment of parameters depends on whether the color is bright and transparent; There is no direct relationship between focusing accuracy and accuracy.

There are three main parameters to be adjusted, namely "aperture", "shutter speed" and "ISO".

So, how should we adjust these parameters?

1- shutter &; hole

Shutter speed and aperture are two basic parameters of SLR cameras, and they are also two terms that beginners should first understand.

Shutter: The so-called shutter speed, in layman's terms, is the time from pressing the shutter button to the end of shooting, that is, the light entry time. The longer the time, the more light, and the brighter the photo. Professionally, when the shutter is pressed, the mirror turns up, the shutter blade opens to make the photosensitive element photosensitive, and when the shutter blade closes, the photosensitive element stops photosensitive. This time interval is called shutter speed, or shutter for short. As shown in the above figure, 1/40 indicates that the shutter speed is one fortieth of a second.

If we hold the camera for more than a few seconds, it is difficult for our hands not to tremble. So long exposure requires a tripod to fix it.

High-speed shutter is very useful when shooting moving objects. Such as fast-moving athletes or animals. We need to use11000 or even faster shutter to keep them relatively still, otherwise they will be burned because they are moving.

Generally speaking, the lowest shutter speed to ensure that photos will not be pasted is called safety shutter. This number is related to the focal length of your lens, and the safety shutter is usually equal to the reciprocal of the focal length; A lens with a focal length of 50mm, a safety shutter of 1/50s, and a telephoto lens with a focal length of 200mm should be at least 1/200s.

This picture shows a swimmer under a high-speed shutter. The shutter speed should be faster than11000 s, so that not only the athletes' movements are frozen, but also the splash is clearly visible.

This is a typical long exposure photography, and the exposure time should be 30 seconds. During this time, many cars passed by, so the photo left the track of the light within 30 seconds, and a car could not be seen.

I'm sorry I didn't find my photo in these two examples. These two pictures were searched from the Internet.

Aperture: Generally speaking, the aperture is the size of the light entrance. The greater the light input, the greater the light input per unit time, and vice versa. As shown in the picture, there is a circular aperture with variable aperture in the lens. This structure is called an aperture. As shown in the above figure, F 1 1 is the aperture value. The larger the value, the smaller the aperture. As shown in the figure below, F22 is less than F 1 1. Please don't be confused.

The relationship between shutter and aperture is like a faucet. Without considering other factors, at the same time (the shutter is fixed), the faucet with large aperture produces more water (large aperture and more light). Similarly, the faucet with the same aperture (fixed aperture) produces more water (the slower the shutter, the more light), as shown below.

This also explains why some novices take dark photos when using M mode, because there is too little light in the aperture and shutter, so the brightness is extremely low and even looks very black.

Use selection:

Large aperture, shallow depth of field, blurred background. Under the same conditions, increase the shutter speed (shoot more people) (for example, F 1.8).

Small aperture, deep scenery and clear front and back. Under the same conditions, lower the shutter speed (shoot a big scene) (for example, F22):

Note: In M mode, the indicator for judging whether the photo brightness is consistent with the actual brightness is the exposure indicator table shown below. The first indicates that the brightness is too high, the third indicates that the brightness is too low, and the second scale value is 0, indicating that the photo is consistent with the actual brightness. Of course, you can choose darker or brighter colors according to different needs.

For example, in this photo, I used the super aperture of f 1.4, so I only focused on chopsticks and tofu wrapped in paste, and the barbecue grill, meat and even bowls farther away in the background became blurred, which is the function of the big aperture.

In the same position, if you shoot with a small aperture above f8, not only the wrapped tofu, but also the barbecue grill and meat in the background will be very clear.

I'm sorry I chose one food ... but I really only found this one.

In short, especially when shooting at close range, if you want to blur well, use a large aperture; If you want to make things very clear and sharp, use a small aperture (for example, taking product drawings in a shed). When the light is particularly good, or when shooting a large landscape, a small aperture is generally used.

Large aperture is also prone to the following problems:

The picture quality is not so good, it will be dizzy easily, not too sharp; Backlight imaging is very weak, even with purple edges; There are black corners all around.

Anyway, the light is good during the day, and it is a long lens, so there is no need to blur it. You can appropriately lower the aperture and pursue better image quality.

2- Shooting mode selection

Before taking pictures, you must first choose the appropriate photography mode. How to choose the mode? What models are there? Please look at the picture below. Every SLR camera has a small circular turntable. Each letter or figure on the turntable represents a different photography mode. Generally, all SLR cameras are equipped with M, A, S and P, which is also the most commonly used photography mode we need to understand first.

M: Manual mode, users can adjust the shutter speed and aperture according to their own needs. Generally, when there is enough time, choosing M mode can not only feel the fun of professional photography, but also take specific shots.

Answer: Aperture priority is automatic. When the user selects the aperture, the system automatically selects the shutter speed to achieve the best effect. This mode is suitable for shooting that needs to change the aperture frequently to achieve focus or change the depth of field.

S: Shutter priority is automatic. The user selects the shutter speed, and the system automatically selects the aperture to achieve the best effect for locking or blurring.

P: The program is automatic, similar to automatic shooting. Shutter speed and aperture are automatically adjusted by the system to achieve the best effect, which is suitable for taking snapshots.

Other modes are scenes set by cameras. Different cameras provide different scenes and are not commonly used. This article will not explain them one by one. It is suggested that beginners take M mode as the main learning content.

3- Adjustment of other parameters

ISO sensitivity: sensitivity (ISO) is the sensitivity to light. You can understand it as forcibly improving the brightness of the photo. When the light is bad, even if the aperture is adjusted to the highest, the appropriate shutter speed may not be reached, so the sensitivity can only be adjusted.

This function is mainly used to assist exposure. The higher the ISO value, the higher the sensitivity. For example, when shooting indoors or on cloudy days, the aperture and shutter adjustment cannot meet the normal exposure, and the brightness can be enhanced by adjusting ISO. However, the higher the ISO value, the more noise there is in the photo. Therefore, when shooting outdoors, the lower the ISO, the better, and the photos will be very delicate. In short, the principle to be followed is that ISO can be low and should not be improved as much as possible. Suggest sunny days 100 or 200, cloudy days 200-800, hand-held and night snapshots 1600, tripod 100.

For example, in this photo, because the light is actually very, very dark, even if I turn the aperture to the maximum (f3.5), the shutter time is still more than 2 seconds or even 3 seconds. In this case, it is impossible to take pictures, and it will definitely be burned. It is impossible for an iron hand to hold the camera for three seconds.

So we must improve our sensitivity. I increased the sensitivity to 2000, and finally the shutter time was reduced to110 second. Although I haven't reached the safety shutter yet, I can barely shoot it.

(Actually, I also reduced the exposure compensation, which will be discussed later. )

Generally, 50-400 is considered as low sensitivity, 400- 1600 is considered as high sensitivity, and above 1600 is considered as ultra-high sensitivity.

As mentioned earlier, improving the sensitivity is called "forcing", and its side effect is that the image quality will be reduced, there will be a lot of noise, and the image quality will be very poor. Generally, the SLR is above 800, and the picture quality of the full-frame machine is above 1600, which will be greatly discounted. So this is the last resort.

Generally speaking, in the day with sufficient light, especially in sunny days, it is recommended to adjust the sensitivity below 400 to ensure better image quality.

Exposure compensation

If the light is really dark, there is no way to ensure a safe shutter even if the sensitivity is improved. Then another way is to reduce the exposure compensation.

We know that digital cameras will automatically calculate how to take photos with normal exposure, and reducing exposure compensation is to change the definition of "normal exposure" in the system. If I lower the exposure compensation by one step, then the system will think that a dim photo is normal.

Looking back at the night scene above, in fact, the brightness of its original picture is probably like the one on the left:

This should have been an underexposed photo, but I reduced the exposure compensation by 1.7ev, which made the system lower the standard, thinking that such a photo exposure was enough. This is the only way, otherwise it will take longer exposure time, and then your hands will shake. As for how to deal with the dim photos, we can use the post-software to brighten them up a little.

Note that this is a more last resort than improving the sensitivity, because even if the dark photos are brightened in the software, the picture quality will definitely be worse. Under normal circumstances, always ensure that the exposure compensation value is 0.

In addition, if you feel that the picture in the viewfinder is obviously brighter or darker than the real situation when taking pictures, you can also directly adjust the exposure compensation. This usually happens when the contrast between light and dark in the picture is very large.

focal distance

The focal length is actually not a parameter, and I also said it together. Most intuitively, the focal length of the camera determines the visual range of the photos we can take, as well as the difference in viewing angles.

However, due to the different sizes of photosensitive elements in different cameras, the meaning of this distance is not necessarily the same. Generally, the focal length written on a SLR lens is based on a full-frame camera. If it is a half-frame camera, it needs to be multiplied by 1.5.

The lens is divided into zoom lens and fixed focus lens. Our mobile phone is a fixed-focus lens. Don't think that you can zoom by taking pictures with your mobile phone. That's completely different from optical zoom. Generally, the magnification of taking a photo with a mobile phone is the same as that of cutting it out after you take the photo. (Except for a few mobile phones equipped with professional optical zoom cameras)

The standard lens of an entry-level SLR camera is a zoom lens with a focal length of 18-55mm (this is a half-length lens, and 1.5 is converted into a full-length lens), which means that it can be changed from a small wide angle to a medium focal length. This is a practical focal length.

Generally speaking, zoom lenses are more flexible; But the fixed-focus image quality is better, the aperture is larger, and it is more suitable for cultivating the sense of lens.

Generally, the focal length less than 18mm is called super wide angle; 18-35mm is called wide angle; 50mm is called the standard focal length, because it is said to be closest to the visual angle of human eyes; /kloc-above 0/00 mm is a telephoto lens.

This is a typical super wide-angle photo, and the focal length should be less than 18mm, so it can be seen that the viewing angle is very wide. If you can shoot half with a normal lens, it is very suitable for showing indoor space.

This big moon must have been shot with a telephoto lens. This focal length should be around 400mm, because the moon is too far away from us. In addition to zooming in on distant objects, we can see that its viewing angle is very narrow, and most buildings only shoot parts, which is also the feature of telephoto.

Personally, I prefer 50mm focus. More than half of my photos were taken with a focal length of 50 mm, such as this one.