Explanation of SLR lens parameter knowledge

SLR cameras have become an important part of many people's amateur cultural life, which has also led to a photography boom in society. It is undoubtedly the most ideal shooting mode to make better use of natural light in SLR camera photography, and the application method of natural light source is an important test for photographers. The following is the relevant information I have compiled for you for your reference!

SLR lens parameter knowledge 1: aperture

In the lens, there is a circular aperture with variable aperture. This structure is called an aperture. The blades that make up the aperture are called. Aperture blade? . (Theoretically, the more blades, the more natural and round Jiao Wai). The aperture on the fuselage is generally f? For example, F8 f 5.6, F 16. We call it aperture value, or aperture for short. The larger the number, the smaller the aperture.

Figuratively speaking, the aperture is the pupil.

The light is dark, the pupils are dilated, and the amount of light entering increases. The light is strong, the pupil is narrowed, and the amount of light entering is reduced.

The aperture size determines the amount of light passing through per unit time. The greater the value of f, the more light passes through it.

The function of aperture is similar to the picture below? Valve? The tap switch is light)

Iso is fixed, the smaller the aperture, the slower the shutter, and the larger the aperture, the faster the shutter.

Conclusion:

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 (use more large scenes) (such as F22).

Theoretically, the larger the aperture is, the better the imaging quality will be, but with the increase of aperture, the aberration will increase sharply, resulting in poor imaging quality. In addition, a small aperture will produce diffraction (in digital photography, a small aperture will increase the exposure time and make the image appear noise), which will reduce the image quality. Therefore, the best aperture value is the balance point to avoid the above two phenomena, that is, the maximum aperture value is low 1 to level 2. For example, 50 F 1.8, reduce it to F4 for best definition!

Optimum aperture:

The best aperture means that any lens, whether fixed focus or zoom lens, has the best aperture or aperture. At this or these apertures, the resolution of the lens can reach the maximum, that is, the maximum resolution can be achieved. The maximum resolution does not refer to the clear range (that is, it is not the depth of field).

The best aperture of an ordinary lens is often in the range of f5.6-f 1 1, so why? No dog head under f8? Statement. And the advanced lens, which is what? Tauren? Its optimal aperture is often relatively large, and even when it is fully open, it may be relatively sharp. This is also one of the reasons why people pay high prices to buy cow heads. They entered the bull's head, not only for the sake of out-of-focus imaging, but also for the pursuit of high resolution under large aperture.

The best aperture of the standard lens of F 1.2-F 1.4 is F4;

The best aperture of the standard lens of F 1.8-F2 is F4-f 5.6；;

The best aperture of F2-F2.8 fixed-focus lens is F4-f 5.6；;

The best aperture of F2.8 constant zoom lens is F5.6

The best aperture of F3.5-F5.6 zoom lens is F8;

The best aperture of F4.5-F5.6 zoom lens is F8-F 1 1.

(Data are for reference only)

note:

? A-file aperture is preferred (photographers often use this file)

1. Whatever you shoot, don't shoot with the maximum aperture unless you want to keep the safety shutter.

2. Please try to use the aperture of F8~F 1 1 when shooting scenery.

3. When shooting close-ups of people and still life, the maximum aperture can be reduced by 1~2.

Please try to control the safety shutter above the reciprocal of the focal length. The wide-angle shutter should also be above 1/30 seconds. If the shutter is insufficient, please increase the aperture or ISO.

Parameter knowledge of SLR lens II: shutter

Shutter is a device for controlling exposure time in camera.

In fact, shutter is short for shutter speed. The so-called shutter speed means that 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. In those years when photography was just invented, it usually took several minutes to take a photo. Most cameras don't need a shutter. At the beginning of exposure, take off the lens cover, then look at the watch. After five minutes, cover it and the photo will be finished.

Later, the photographic speed of film became faster and faster (ISO became higher and higher), and the exposure time became one minute, several seconds,110 second or even one hundredth of a second. It's not fast enough to hold the lens cover by hand at this time. We need something that can accurately control the exposure time, and this thing is the shutter. Shutters include mechanical shutter, electronic shutter and electromechanical combination shutter.

Security shutter: What is a security shutter? The reciprocal of the focal length.

For example, when using a 35mm lens, the shutter speed should not be lower than 1/35s, and when using a 200mm lens, the shutter speed should not be lower than 1/200s, otherwise the picture may be pasted. (Some lenses have anti-shake function, which can still reduce the shutter speed 1-2 under the safety shutter. )

If you take a snapshot, you need shutter priority. (Improve iso, short focal length, large aperture, tripod, and all other tools that can accelerate)

1/4000 shutter can capture the moment.

B-door function, from pressing to releasing, shutter opening and closing time is controlled by yourself. ：

Knowledge of SLR lens parameters III: ISO sensitivity

ISO sensitivity: refers to the photosensitive capacity of photosensitive elements. In the film era, the sensitivity is constant, and a film has only one sensitivity. Because the film is produced by the factory, the amount of silver salt on the film has been decided and cannot be changed. In the digital age, CCD/CMOS is a photosensitive element, and the current generated after receiving light can be adjusted by an amplifier, so the sensitivity is variable. The abbreviation of sensitivity is ISO. The higher the sensitivity, the stronger the sensitivity of the photosensitive element. Under the same aperture shutter condition, the higher the sensitivity, the brighter the picture.

Under the same conditions, the lower the ISO, the better the picture quality! The higher the ISO, the faster the shutter!

Although the high ISO is fast, the enlarged image is rough (that is, the noise is large), so it is impossible to draw a fine picture. Therefore, landscape photography should use the lowest sensitivity! Use high ISO only as a last resort!

For D3 100: It is recommended that 100,200 be sunny. Cloudy day 200? 800, hand-held at night, snapshot 1600, tripod available 100.

SLR lens parameter knowledge 4: metering and exposure

Photometry is a machine to judge the intensity and brightness of light.

Measurement method: generally, it is matrix, central and point measurement.

1. Don't point to the sky, don't point to the darkest place. Grab the middle value.

2. Because the machine is convenient in the later stage, the automatic exposure will be underexposed, resulting in gray, white and black. Therefore, it is necessary to increase the exposure when encountering white, and reduce the exposure when encountering black!

3. Make good use of measurement methods (weighing measurement, point measurement, center key measurement ...) according to the subject matter you shoot.

4. If you are not sure about metering, please lock the gray things around with AE lock before shooting.

5。 For M file, photometry is invalid, but it will affect the information prompt of LCD histogram.

Manual metering:

1. Find the block in the picture that is close to 18% gray level.

When the shooting experience is gradually accumulated, it is easy for us to find the place where the reflectivity is close to 18% in a picture. It may be the sky, the asphalt pavement in the sun, the green grass, or the unpainted wall. Experience can help us to confirm on-site metering. You should do more, then observe the results and correct your judgment.

2. Use a gray card or palm to measure light.

If you don't have experience to judge the middle tone or the environment is chaotic, you can directly put the gray card under the ambient light source to directly measure the light. If there is no gray card, you can use your own palm instead. People's skin color is close to the gray tone of 18%, so the hand is actually a very useful gray card. But remember not to use the suntanned back of your hand. This will affect the photometric results.

Exposure accuracy:

When shooting, accurate exposure is the key to obtain high-quality images. Later software made up for incorrect exposure errors, but it was difficult to achieve satisfactory results.

The image with accurate exposure has natural tone and saturated and bright color;

Insufficient exposure, dark image and serious loss of dark order;

Overexposure, the highlight part of the image has no hierarchy.

1, shooting against the light, but not pursuing the silhouette effect.

You can use a reflector or flash to supplement the light of the subject. If it is too far away from the subject, you can use the spot metering function to accurately measure the light of the subject, or you can use the exposure meter to measure the incident light near the subject.

2. The subject is in front of a big white background.

Because a large area of white or light background will seriously affect the accuracy of the exposure meter, in this case, we can choose other medium-gray objects with the same direction and brightness to measure light. If the reference object cannot be found, the exposure compensation can be appropriately increased. As for the added part,

Less exposure depends on the proportion of white background and the intensity of light contrast when shooting in the field, generally between 1-2.

Step 3 shoot small objects in front of a black background

When the subject is in a black or dark background, because the black or dark background will absorb a lot of light, if the average metering mode or multi-zone metering mode is used, it will lead to serious overexposure, so the spot metering mode should be used to meter the subject. If the camera has no spot metering function, negative exposure compensation can be used to solve the problem. Generally speaking, the exposure compensation value is determined according to the intensity of light shining on the subject.