Photography starts with the mobile phone (1 1) and takes photos.

After taking photos, sometimes we need to post-process the photos. Through post-processing, you can make secondary composition, adjust exposure, control light and shade, adjust tone and so on. Post-processing is also a skill that photographers must master, and it is also a difficult point in photography learning. First of all, you should understand the basic knowledge in post-processing and master them, which can make your photography skills go to a new level.

In the diagnosis of Chinese medicine, doctors diagnose the condition by looking, smelling, asking and feeling. Then in photography, we can judge whether the photo exposure is correct by histogram. In some picture viewing software or PhotoShop software, the histogram of photos can be displayed.

Take Huawei mobile phone as an example. After selecting a photo in the gallery and opening it, click the circular "I" icon in the upper right corner to view the histogram of the photo.

The histogram is a coordinate system, and the horizontal axis represents the brightness arrangement of each pixel in this photo, from left to right, from black to gray, and finally to white. Pure black is 0, pure white is 255, and there are 256 brightness values from black to white. The ordinate represents the relative number of pixels corresponding to each brightness value in the photo.

The picture shows the histogram of black, white and gray pictures. From the histogram, three columns are formed, and there is no connection between them. You can see that the three colors of black, white and gray in the photo have no transition directly.

The picture shows a 256-level gray picture and its histogram. The histogram is even and coherent, and there is no fault, indicating that the photo contains pixels from black to white (brightness is 0-255).

The picture shows the histogram of high-profile photos. The data in the histogram is biased to the right (white area), and there is no data on the left (black area) and the middle (gray), which is consistent with the picture we see.

If it's a histogram of low-key photos. Black occupies most of the area in the picture, and the data in the histogram is close to the black area.

By observing the histogram, we can easily judge whether the exposure of the photo is appropriate, which provides reference for us in pre-shooting and post-processing.

The picture shows the photos and histograms of normal exposure. The environment of the cab is dark, so the driver looks a little underexposed and can't see the details clearly. The whole histogram is like a mountain peak, which is high in the middle and low on both sides, indicating that there are few black and white in the photo, most of which are gray pixels with different brightness values, and the photos are rich in details.

The picture shows underexposed photos and histograms. The overall picture is dark, and the area of the left half of the histogram is larger than that of the right half. The leftmost line is close to the border, indicating that a part of the picture is pure black without any details, which is what we call "dark overflow".

The picture shows overexposed photos and histograms. The driver of the cab has been exposed normally, but the body and sky have been seriously overexposed and the details have been lost. From the histogram, the area of the right half of the histogram is larger than that of the left half, and the rightmost line is close to the border, which means that part of the picture is pure white without any details, which is what we call "bright overflow".

Histogram plays an important role in the post-processing of photos, and special attention should be paid to the situation that light overflow or dark overflow cannot occur.

Hue, lightness and saturation are called the three attributes of color. Hue refers to the name of the color, also called the appearance of the color, such as red, green and blue. Saturation refers to the purity or brightness of a color. Brightness refers to the relative brightness of colors.

The picture shows the contrast of red saturation from low to high.

The picture shows the contrast of red lightness from low to high.

complementary colour

In the color wheel, when the included angle between two colors is between 150 degrees and 180 degrees, the two colors are complementary colors. For example, red and blue, red and green are common complementary colors.

The picture shows the complementary colors represented by the color wheel.

One of the principles of complementary colors is that when the eyes or brain perceive the complementary colors of a certain color, they are balanced. In photos, the strong color contrast of complementary colors will bring obvious color contrast effect. In practical application, one color is often used to set off the scenery of another color.

The red flowers in the picture form the most common complementary colors on the green background.

Adjacent color

Adjacent colors refer to two colors adjacent to each other in the color wheel. The visual experience it brings is harmonious and stable. Adjacent colors represented by the color wheel.

In the early autumn forest, yellowed and yellowed leaves form yellow-green adjacent colors.

warm tone

Warm colors include red purple, red, red orange, orange, yellow orange, yellow, yellow-green and other colors. Warm colors are similar to the colors of the sun and flames in nature. It has obvious visual tendency and can express the feeling of warmth, enthusiasm, expansion and progress.

cool tone

Blue, turquoise and blue-purple are all cool colors. The picture shows the cool color system represented by the color wheel. Cool colors can give people a fresh, natural, comfortable and shrinking visual feeling. Compared with warm colors, cool colors are less likely to cause visual fatigue. Representative scenery includes mountains, blue sky and water.

The current photo processing software is highly intelligent. There is LightRoom software on the computer, with a large number of presets built in, which can be directly applied to photos to preview the effect. On the mobile phone, taking Huawei mobile phone as an example, many effects are preset in the photo editing software that comes with the system, and users can apply different effects according to their own preferences.

Compared with these automatic post-processing, only some manual adjustment options are discussed here, including brightness, contrast, saturation, sharpness, bright part (highlight), dark part (shadow), color temperature (warm tone) and atmosphere adjustment items.

If you don't use Huawei mobile phone, I recommend you to use professional mobile phone photo processing software Snapseed, which is purchased by Google and provided free of charge. Although the name is in English, the operation interface is completely in Chinese.

Tone range

Tone reflects the change of light and shade in the photo. Tone range is from the darkest to the brightest, generally divided into black, shadow, midtone, highlight and white.

Take an evenly distributed black-and-white gradient picture as an example to show the corresponding part.

Bright part (highlight)

Bright parts, also called highlights, can be considered as areas with high brightness in the image, and these areas also contain a lot of details. Sometimes photos are overexposed, which can reduce the highlight value and retrieve some missing details. But the specific situation is not only related to the photo format (jpg or raw), but also related to the photosensitive components of the camera/mobile phone.

Dark part (shadow)

Dark areas, also known as shadows, are usually dark areas in the picture but still retain some details.

(written) in black and white

Black is the area with brightness of 0 in the image, and the black area has no details. White is an overexposed area with no details in the image. It's not necessarily white.

neutral tone

Midtone is the middle range of an image that is neither dark nor bright, and contains many details.

clever

Brightness refers to the brightness of light on a scene or image. When the brightness of the image increases, it will appear dazzling or dazzling, and when the brightness decreases, the image will appear gloomy. Adjusting the brightness can change the overall exposure value of the photo. Although it is easy for us to judge whether a photo should be brighter or darker, due to the influence of the brightness of the mobile phone screen, it is best to combine the histogram to adjust the brightness of the photo.

contrast

Contrast refers to the difference between different colors. The greater the contrast, the greater the contrast between different colors, which is black and white. If the contrast is too large, the image will look dazzling. The smaller the contrast, the smaller the contrast between different colors.

Saturation capacity

Saturation refers to the density of image colors. The higher the saturation, the fuller the color, which is called green feeling. The lower the saturation, the darker the color will appear. When the saturation is 0, the image is a grayscale image.

acutance

Sharpness is used to indicate the contrast of image edges. Images with high sharpness look clearer, but in fact, the increase in sharpness does not improve the real resolution.

After the sharpness of this picture is increased, it can be clearly found that several stripes with different brightness are added on both sides of the light-dark boundary line to highlight the edge and achieve the purpose of increasing clarity.

After excessive sharpening, there will be obvious separation boundary at the edge of the image, and light and dark halo will appear around the line segment. In portrait photography, excessive sharpness enlarges and highlights the small scars and papules of human skin (that is, it is more obvious than the actual naked eye), resulting in rough and dry face. Therefore, in portrait photography, we should choose moderate sharpness instead of blindly pursuing high sharpness.

atmosphere

Atmosphere is a unique adjustment option in Snapseed software, which is actually a comprehensive adjustment. With the increase or decrease of atmosphere, the photo style will change, and the biggest difference is reflected in highlights and shadows.

Let's take the photo of the truck driver just now as an example to introduce the simple post-processing process of the mobile phone.

The photos I processed are as follows. According to different personal preferences, everyone has different effects.

Photography starts with mobile phones-content

1. Mobile phone is the best entry tool for photography.

2. The difference between mobile phone and SLR camera photography

3. What is a good photo?

4. Talking about the art of photography

5. Key factors affecting mobile phone photo taking

6. Basic theory of exposure

7. Understand photographic composition

8. Master the composition of portrait photography

9. Composition of actual combat scenes

10. The mystery of light

1 1. Post-photo foundation