Photography starts with mobile phones: 02 the difference between mobile phones and SLR cameras.

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

In the era of film cameras, it was film that was responsible for recording light. In the era of digital cameras, the electronic component for recording light is CCD. CCD in digital camera refers to "charge coupled device", which is an image sensor that converts optical signals into electrical signals. The photosensitive element in the mobile phone is CMOS.

Generally speaking, the larger the size of CCD, the more photosensitive elements it can hold, the more photons it can capture, the better the photosensitive performance and the lower the signal-to-noise ratio, which means the better the imaging effect, that is, the image is fine, the layers are rich, and the color reproduction is true. Under the same conditions, more image details can be recorded, which means better image quality. This is the old saying that "the bottom layer crushes people first." However, the processing and manufacturing technology of large-size CCD has high requirements and high cost. Therefore, the size of CCD used in different digital devices is different. From mobile phones to entry-level digital cameras, from high-end Quan Huafu SLR cameras to medium format digital cameras, the sizes of CCD are quite different. For example, Huawei P20 Pro's 40 megapixel camera has a photosensitive element size of11.73 inches, and Canon's full-frame camera 6D has a photosensitive element size of 36 mm X24 mm ..

The size of CCD is the main factor that determines the picture quality. With the improvement of manufacturing technology, more electronic components can be integrated in the same area, so the pixels integrated by CCD are getting higher and higher. However, there are also software technologies to improve pixels. For example, the photo taken by a mobile phone under normal conditions is100000 pixels, and the photo output by software interpolation algorithm is 40 million pixels. In this case, the improvement of image quality is very limited.

From the principle of CCD/CMOS, due to the inherent CMOS size of mobile phone camera is insufficient, the photosensitive ability is weak. In the case of good light, such as outdoor sunshine, the difference between the photos taken and those taken by SLR is very small. In the case of weak light at night, CMOS can't receive enough light, so the photos taken are noisy. When taking photos with your mobile phone, you must pay attention to the influence of the intensity of ambient light on the photos.

We often hear the expressions of wide-angle lens and telephoto lens. The "focus" here refers to the focal length of the lens. The length of the focal length of the lens determines the imaging size, viewing angle, depth of field and viewing angle of the picture. The focal length of a lens is a very important index of the lens.

The focal length of the lens determines the imaging size of the object on the imaging medium (film or CCD, etc.). ), which is equivalent to the proportion of objects and images. When shooting the same subject at the same distance, the image with long lens focal length is large, and the image with short lens focal length is small. According to different uses, the focal length of camera lens varies greatly, from a few millimeters to a dozen millimeters to several meters.

With the same shooting distance and different focal lengths, the differences of the images taken are as follows. As you can see, the smaller the focal length, the wider the viewing angle, and the more content you shoot. A lens with a focal length of 24-35mm is called a "wide-angle lens", a lens with a focal length less than 20mm is called a "super-wide-angle lens", and a lens with a focal length greater than 100mm is called a "telephoto lens".

According to the conversion, the focal length of the lens on a general mobile phone is equivalent to 27mm or 32mm of a full-frame camera, so it belongs to a wide-angle fixed-focus lens. The advantages of wide-angle lens are short focal length and large viewing angle. You can shoot a wide range of scenes at close range, and the prospect is more prominent. The range of depth of field is obviously larger than that of standard lens and telephoto lens, and the picture has a strong stereoscopic effect. Suitable for indoor close-range shooting, shooting mountains, rivers, buildings, crowds and other scenes. When using wide-angle lens for close-up, the foreground is exaggerated, which will produce serious perspective distortion.

What is scaling? As the name implies, you can change the focal length of the lens. Stand still, turn the lens to telephoto, and you can take distant scenery, and turn it to wide angle, and you can take photos with a wider angle of view. It is said that both SLR cameras and mobile phones can zoom now. Are they the same zoom?

Friends who have played SLR know that zooming can be achieved by twisting the zoom lens or zoom ring when shooting. This zoom form of SLR cameras is called "optical zoom". Visible, optical zoom is through the change of physical focal length to achieve far-near shooting, without changing the resolution of the photo, the pixels of the photo remain unchanged.

When the mobile phone is shooting, two fingers slide on the screen to zoom in. Isn't that zoom? Yes, but this zoom is different from the optical zoom of the camera. The zoom of mobile phone is digital zoom. This zoom is achieved by interpolating and enlarging some pixels on the original image sensor. To put it bluntly, it means not changing the focal length of the lens, but forcibly enlarging the pixels! Otherwise, the quality of the mobile phone after "zooming" can't bear to look straight! From left to right, the picture below shows the comparison of photos taken with no zoom, 10x optical zoom and 10x digital zoom respectively.

For example, iPhone X can take photos of F 1.8 from a wide angle, and telephoto can take photos of F 2.4. This dual-camera zoom is obviously better than lossless zoom. But then again, the two lenses of dual-camera zoom are essentially fixed-focus lenses, not zoom lenses.

The so-called "lossless zoom" of many mobile phones actually uses the special design of photosensitive elements to achieve the "zoom" effect through single Juck Zhang high pixel or multiple cuts. The so-called "zoom" of a mobile phone is not a real zoom, but a zoom effect is achieved by cutting or double shooting. After "zooming", both pixels and image quality will be affected, which is essentially different from the optical zooming of a camera.

Aperture is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens. Usually in the camera. For the manufactured lens, we can't change the diameter of the lens at will, but we can control the luminous flux of the lens by adding a polygon or circular aperture grating with variable area inside the lens. This device is called an aperture. Its size determines how much light enters the photosensitive element through the lens. We use f value to represent the aperture size, where F= lens focal length/lens effective aperture diameter. Aperture f value = lens focal length/lens aperture diameter.

Simply put, the purpose of taking pictures is to get the correct exposure, so whether a lens is good or not has a certain correlation with the light in the photos he takes. Due to space constraints, the CMOS size of mobile phones is smaller than that of cameras such as SLR, so the amount of light entering is less. In order to solve this problem, mobile phone manufacturers will choose large aperture cameras in addition to large-size CMOS. For example, the two cameras behind Huawei Mate 10 all use F 1.6 aperture.

As we know, the aperture value is generally expressed by the f value. The larger the F value, the narrower the opening, the smaller the aperture and the less light entering. Conversely, the smaller the F value, the wider the opening, the larger the aperture and the more light entering.

In addition to the amount of light, the aperture value also affects the background blur effect of mobile phone manufacturers who like to make an issue. Theoretically, the larger the aperture value, the more obvious the blurring effect of the background, and the smaller the aperture value, the smaller the blurring effect of the background.

However, it should be pointed out that unlike cameras, the focal length of mobile phone lenses is often short, so the depth of field created by taking macro photos only with cameras is usually weak. Therefore, the aperture value of the mobile phone camera does not completely correspond to the aperture value of the camera lens.

Take the mainstream f/2.2 aperture of mobile phones in recent years as an example. Its blur effect is only equivalent to the f/ 13 or f/ 14 aperture of a full-frame camera, so if you only use the lens aperture to take macro photos, the background will only be blurred a little. However, the blurring effect of the so-called comparable SLR, which is the main focus of mobile phone manufacturers, is mostly realized by software algorithms, so there will be embarrassing situations such as incomplete edge tailing and unnatural blurring effect, which is more like adding Gaussian blurring effect after a P-picture. Some mobile phones shoot separately through multiple cameras, and then synthesize by software to imitate the effect of lens blur.

Unlike SLR lenses, the aperture of a mobile phone camera cannot be adjusted. Today's smartphone cameras all use fixed apertures. No matter what scene you shoot, this aperture is fixed and cannot be adjusted manually or automatically.

The so-called depth of field is the range that can still be clearly seen before and after the focal length is aimed at a certain point. It can decide whether to blur the background to highlight the subject or shoot a clear background. Simply put, a small depth of field can take photos with blurred background, and a large depth of field can take photos with clear background. The relationship between aperture and depth of field is that the larger the aperture, the smaller the depth of field, and the smaller the aperture, the greater the depth of field.

Here, the photographer focuses on the alarm clock in front. The top left picture uses a large aperture of f/2, correspondingly, the depth of field is small, and the other two distant alarm clocks are out of focus. In the picture on the right, a lens with the same focal length is used in the same position, but the aperture is changed to a smaller f/ 16. More parts of the transformation became clear. Changing the aperture size is the best way to change the depth of field, because other aspects of the image will not be affected.

In fact, the focal length also affects the depth of field. The longer the focal length of the lens, the smaller the depth of field. The shorter the focal length, the greater the depth of field. The shorter the focal length of the lens, the greater the depth of field. The picture on the left below uses a 135mm lens, and only the close-up subject is clear. In the picture on the right, the same position, the same aperture, set the focus at the same position as before. A 50 mm lens will make the subject in the background clearer. Observe the influence of the change of focal length on the viewing angle (the number of scenes contained in the picture) and the size of things in the picture. The clear range of the two photos is obviously different.

The farther the lens is from the subject, the greater the depth of field. In the picture on the left below, the focus distance is about 1 m, and only a narrow range from near to far is clear. In the picture on the right, use the same focal length and aperture, but retreat to a place 3 meters away from the subject to focus on her again, and more places in the picture become clear. The effect of retreating is similar to that of shortening the focal length. More scenes are displayed in the picture, and more parts of the image become clear.

The focal length of the mobile phone camera is fixed, and the physical focal length is only 4-5mm, so it is difficult for the mobile phone camera to take photos with shallow depth of field. At this time, some skills are needed-try to get close to the subject and let the subject and the background form a certain distance. Although the effect is not so obvious on professional cameras, the large aperture does bring more interesting elements to mobile phone cameras.

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