What is the concept of 18 shades of gray in photography?

18 shades of gray in photography.

Second, the meaning is two.

The first layer of photogrammetry uses 18% reflectance as the reference value for bursting. (Because the metering system commonly used by the camera is based on the gray of the 18-degree gray board, but when the measured value of the pure black subject or the pure white subject is compared with the 18-degree gray board, there will be a great error, resulting in the actual metering value will be ** over- or under-exposed!) Reference**.

How to meter. Method.

First of all, make sure that the light hitting the gray board is basically the same as the light hitting the subject. Both should be of equal strength. For example, when the subject is standing in the shade of a tree, do not meter the gray board exposed to sunlight.

If the subject is in the shade of a tree, the gray board in the shade of the same tree is metered.

Secondly, we may notice if the photographer's hand is projected on one corner of the gray board. If our subject is exposed to sunlight at this point, make sure that we are not measuring this shade.

Thirdly, the gray board we bought in the store was about 8 inches 10 inches in size, which seemed too big to fit in a camera bag. Don't be embarrassed, cut it in half or cut it into four pieces, just put a small piece in your bag. The size of the gray board is sufficient if it can be metered at close range when shooting.

Fourth, use a handheld light meter to read the gray plate data. We can also use the built-in light meter in the camera to read the gray plate, and the effect is the same.

Fifth, even if our cameras have automatic** capabilities, we can still use grayboards. If our camera provides the ability to lock onto a reading, you can do the following:

First, read the gray board data at close range and press the ** lock.

Then, while locking this amount in place, point the camera at the scene you want to shoot and take a picture. If the light that illuminates the scene is the same as the light read from the grayboard, then it is correct.

Sixth, we may notice that there is a similarity between the grayboard reading and the incident light reading, and indeed, both of them should provide the exact same recommendation**, both of which measure the light that illuminates the subject. When we do the incident light measurement, the white plastic cover on the light meter allows 18 of the light to pass through, which is exactly the same as taking the reflected light measurement on the gray plate. The gray plate reflects 18 rays of light that shines on it.

If the illumination light is the same, then both readings should be the same.

And if you're using a hand-held light meter like the Shiguang 608 with white balls, you don't need to use an 18-degree gray board, because that's the equivalent of an 18-degree gray plate!

The second layer is the digital age (only for digital cameras).The role is used to customize the camera white parallel. The settings vary from camera to camera.

The setup of the same brand is generally the same. I won't say much about it here. You explain your camera model, and I can tell you how to listen.

That is, the shadow tone value of the image is consistent with the 18% gray standard plate, and the color value on the object represented by this gray is not fixed, it may be white, black, gray or other colors, but according to the results measured by the light meter for "V (five) zone**", the "shadow tone value v" will be obtained on the photo, and the shadow tone is consistent with the standard gray plate.

That's because the light meter is corrected to a benchmark of 18% of the gray value of reflectance of the average of the surface of the object.

The partition method is an important method of Adams's artistic creation, which is based on the theory of accurate testing (light meter, aperture, shutter isolinearity, accuracy, etc.), the characteristics of film or CCD, the characteristics and control of photographic paper, the complete color management of modern digital, the characteristics of developer, and so on. It's a complete process, and missing one of these links will affect or even fail to achieve the effect you want.

So when you are still in the stage of just pressing the shutter and not doing the later stage and not printing it yourself, you just need to know the theory.

1 In most cases, if the lighter part of the picture can be mixed with the darker part, the final hue must be an intermediate gray, which is what we call 18% gray, and is the benchmark for the operation of all camera light meters. Ansel Adams, the originator of 2 photography, divides the hue and gray into 10 levels, and the picture of the 5th area of 18% gray is not too bright or too dark, which can be described as just the right area. 3 In more layman's terms, whether you are measuring a white or black object, the camera will determine the ** value according to the gray color that can reduce it to nearly 18%.

Medium gray is the skin tone of a Caucasian person in black-and-white photography and is used to define white balance and metering. If you only use it to define white balance, any gray color will do.

18% refers to the reflectivity, and the gray with 18% reflectivity is exactly the medium gray (that is, the gray in the middle).

In photography, medium gray is the basis of the metering system, and the camera metering system looks at the brightness of all objects in nature as medium gray.

Therefore, in the actual shooting, it is necessary to "add white and subtract black".

The intermediate gray principle of photography** --- 18 gray scales.

Friends who play photography know that many traditional film cameras, especially digital cameras, have automatic aperture devices, which brings great convenience to us to take pictures correctly. But auto-iris is not a panacea, and there is no guarantee that every image will be correct. Shooting with the automatic aperture is either insufficient or excessive, which makes the shooting dark.

Why is this happening? This has a lot to do with not understanding the intermediate gray principle and not using the automatic device correctly. The basic principle of the automatic aperture device is that the brightness of the photographed object is first measured by the metering system built into the camera, and then the measurement results are transmitted to the chip, and then the chip is transmitted to the automatic aperture device to give the appropriate aperture to complete the task.

The so-called intermediate gray principle means that whether the in-camera photometric system measures a subject with high brightness (such as unpolluted snow) or a subject with very low brightness (such as coal), if the subject is processed normally according to the measured results**, the subject will produce an intermediate density on the negative. The ** washed out with the medium gray density negative is used to obtain the intermediate gray shadow tone, that is, the medium gray density negative produces the medium gray shadow **.

According to the principle of intermediate gray, according to which part of the scene**, what part will produce intermediate gray shadow tone. The brightness distribution of the scenery in our shooting practice is very complex, for example, we shoot a picture like this**: take a half-length portrait with the blue sky, white clouds and green grass as the background, if you shoot in the light, you can get the correct ** with automatic aperture**, if the backlight shooting is not compensated, **insufficient, the face is black, because the metering system in the machine measures the average brightness of the scene, not the brightness of the face.

The brightness of the snow is very high when shooting snow scenes, and the height of the snow is **, which produces a medium gray brightness on the negative, and when it is washed out, it will get a medium gray tone, and the snow scene becomes a gray scene, losing the texture of the snow. When shooting snow scenes, you need to press the shadow part of the snow**, that is, open the aperture appropriately to maintain the texture of the snow. Some photography textbooks say:

Shoot snow scenes because the brightness of the snow is very high, shooting with an automatic aperture is easy to overshoot, so you should shrink the aperture appropriately. This is contrary to the intermediate gray principle of **, and it is also a misleading.

Just know how to use it. Generally, it is used with gray cards and light meters. It is also possible to use the camera's built-in metering system, but it is not as accurate as the light meter.

Understanding 18 degrees of gray is not to read New Zealand, but to read Adams's regional ** method, this is not just a matter of evaluating photometering**, this is all there and there! Modern digital cameras can use the area** method to guide shooting, but this only uses a portion of the metering. Except for manual spot metering, all other metering methods with digital cameras are automatic shooting with the camera instead of your head!

The camera automatically finds out the average value at that time according to the light on the scene to decide**"?? This automatic find** is not accurate ** in most cases, at most it is just what you think is appropriate**.

That's right, the camera first calculates the average brightness of the entire picture of the sensor in the camera, if it is lower than 18 gray scale, increase the ** amount, if it is higher than 18 gray scale, reduce the ** amount.

Therefore, there is a saying of "white plus black subtraction" in the **, because the local brightness in the bright light is too bright, which raises the average value, the camera will adjust the ** too low, and the brightness of the picture is not enough, so in the environment where the brightness contrast is too large, the metering value of the camera needs to be increased as the final ** value. If something is too dark, it will be the other way around.

Your understanding is correct, I just want to tell you that in the picture the light ratio (the largest ratio is the smallest) is greater than 3, the camera's metering is inaccurate, and you need to adjust it according to "white plus black minus" and your own experience.