Teach you how to get the best exposure
- Oct 25, 2019
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Correct exposure is critical for taking excellent natural photographs. Correct exposure should avoid overexposure of highlights. There are very few noise points in dark areas. Pixels capture enough light to ensure accurate color restoration. The final exposure is determined by the photometric function of the camera, the aperture of the lens and the shutter. However, many times, cameras need help to get the best exposure, so you need to learn these methods.
Fortunately, the exposure control of digital cameras is much easier than that of flip-flops. Digital cameras allow you to see pictures immediately, so you can use highlight warnings and histograms to determine whether exposure is correct or not. You don't have to think twice about whether the exposure is "out of order" because highlight warnings and histograms are already displayed for you. Although exposure with digital cameras is easy to control, it's still helpful to master the basic principles of exposure. It is necessary to understand aperture values, shutter speeds and how they work together. It is also important to know the advantages and disadvantages of different photometric modes. You have to learn why some objects need exposure compensation and how to operate them. Digital exposure requires you to retain details in most highlights (metal reflections are no exception) and in dark areas. The dynamic range between light and shade can be fully recorded by digital sensors. There are about six apertures. Digital exposure can be displayed instantly through highlight warnings and histograms, so it's easy to adjust exposure when taking still life until you get the picture you think is accurate. You can even use a series of different exposure values, especially when it's not easy to shoot, and then delete the worthless images. Digital images in JPEG and RAW formats can be optimized by post-exposure software, but they are not perfect.
I. RAW and JPEG format pictures
Before discussing exposure in detail, it is important to know which image file format you intend to use, because there is a slight difference between the two under the right exposure. Two common file formats are JPEG and RAW. JPEG format is a lossy file format provided by the camera for obtaining sharpness, saturation, white balance, contrast and gamut. RAW format file is unprocessed data transmitted by sensors. It is a set of file formats. Each manufacturer has its own proprietary RAW file format. Canon cameras use. CR2 and CRW formats, Nikon cameras use NEF format, Olympus cameras use. ORF format, Fuji uses. RAF format, other cameras also have different formats. A RAW format file must be converted by software to achieve the best quality. There is a great deal of controversy about which format is best. This debate is interesting, but there is no correct answer. Both formats can be used for a photo. Before we decide which format to use, let's look at their advantages and disadvantages. Advantages of JPEG. JPEG pictures are processed directly by the camera, so time can be saved. They occupy less storage space. The camera's buffer clears quickly, so you can keep shooting. JPEG files are smaller than RAW files, and the maximum continuous shooting speed is much higher, which is suitable for motion photography. The disadvantage of JPEG: Data loss occurs when JPEG is first generated, and it will happen every time it is stored. * 8-bit data limited by JPEG format can lead to tone separation. This means that you may lose continuous tones and result in image stripes, especially when you use software to edit pictures in large quantities. The process parameters such as color space, white balance, contrast, exposure, hue and sharpness are locked in the document, which will reduce your ability to adjust software later.
Advantages of RAW - Because these files contain raw data from sensors, they have great control over white balance, sharpness, contrast, color space, saturation and exposure. * RAW format files are much larger than JPEG's 8-bit data, which gives them an advantage in later image optimization (without losing the lasting tone). RAW format converter has excellent adjustment function in noise control and lens correction.
Disadvantage of RAW: Large files can quickly fill up the memory card. * The number of consecutive photographs decreased dramatically. * Must be via RAW file converter, so it's time-consuming.
2. Which file format to choose?
The answer depends on your needs. If you require quality and don't want to spend time processing RAW files, high quality JPEG is the best choice. Of course, you need to make sure that the exposure is correct and that there is a proper white balance, because once the shooting is completed, it will be difficult to adjust later. Many cameras offer a variety of JPEG formats for your choice, preferably the highest quality one. If you want to use a low-quality JPEG image for the network, it's very simple to convert from high-quality to the size of the image you need. If you love the late stage of the computer and want to produce large pictures of the best quality possible, shoot them directly into RAW files. RAW files provide more control over adjusting exposure, color, contrast and white balance. As you know, we use large format JPEG files to photograph friends'gatherings and things that do not require the highest image quality. We intend to give photos to people at any time. For serious nature photography, we only take images in RAW format. Take lots of pictures, edit them hard, and keep the best ones. I'm not suggesting that professional photographers don't take JPEG pictures. Professional sports photographers mainly shoot JPEG files, because they need to use pictures quickly during the deadline, and the high speed of reading JPEG files will help shoot wonderful action moments.
Two reticulated giraffes put their heads together casually, and the interaction between wildlife often provides us with the opportunity to take excellent pictures.
3. Correct Exposure of JPEG Files
Photographing JPEG files really requires perfect exposure. Because of the smaller recording depth, a lighter or darker point in JPEG photography can cause various problems, such as the loss of continuous tones. If possible, avoid clipping the left and right sides of the histogram. In most scenarios, it is preferable that the right side of the histogram begins to approach the right side, not necessarily on the right edge, but the image data is expected to be recorded in the right-sided area of the histogram center. If the contrast of the scene is very strong, it is unavoidable to cut, then cut the black part of the left or histogram of the picture, try to retain the detail level of the right highlight.
For digital photographers, it is important to keep the details of the white feathers of the trumpet swan. Make sure that the histogram data is close to the right but not cut.
IV. Correct Exposure of RAW Images
Unlike JPEG photography, which requires correct exposure, RAW file adjustment has great tolerance for exposure. Through the software, the exposure can be adjusted to no more than 1 gear overexposure or 2 gear underexposure. Essentially, RAW files, like film negatives, can almost (within a certain range) make exposure as perfect as returning to the scene through software adjustments. Although RAW files can be optimized for exposure, it still takes time and may lose some quality. There is another way to get the best exposure of RAW files. Using histograms, it's easy to know if your exposure is perfect. Your goal is to record data on the right side of the histogram, as far as possible without touching the right edge. Curves on the right edge are called highlight spillovers, because overexposed pixels show little or no detail. If a pixel does not record details, there is no way to reproduce them. Similarly, avoid the histogram curve concentrating on the left as much as possible. Obviously, if you take pictures with all-black areas, they are represented by the concentration of pixels on the left side of the histogram. For most pictures, you should keep the histogram from the right part where there is no highlight overflow to the left edge. Exposure methods for RAW file images are often referred to as "right exposure". Exposure in this way will give your RAW digital file image great flexibility and more details. When this method reduces the digital noise of the image and improves the signal-to-noise ratio, the sensor will measure the light more accurately. I can talk a lot about noise and SNR, but if your RAW image is near the right of the histogram and there is no highlight spillover to cut any details, you really don't need to know that.
5. Help you get the best exposure
Histogram is the key to determine whether you get the best exposure. At first glance, histogram may be difficult to understand. It is actually a very simple exposure data histogram, which is a graphic representation of exposure. This image is a 256-level gray scale along the horizontal axis, ranging from the left-most pure black value 0 to the right-most pure white value 255. The vertical axis represents the pixel value of each brightness level in level 256. If the image is overexposed, a peak is seen at the far right of the histogram. This peak represents overexposure of these pixels. Generally speaking, avoid overexposed pixels, because they record little or no details. Nevertheless, mirror reflections like metals or water surfaces do not have details, so it is also possible to take pictures of these materials with a small peak on the right of the histogram. Also try to avoid peaks on the left-most side of the histogram. Such peaks also mean that the pixel does not record details, because the light is too dark, so the pixel does not record much light data. However, when there are dark or shadows in the scene, there will also be a peak on the leftmost side. Later software can brighten or darken to adjust exposure, but if there are many dark pixels, it will lead to digital noise, that is, these pixels appear unexpected color spots or brightness values compared with adjacent pixels. The peak value of the left-most or right-most pixel of a histogram is often called a fault phenomenon and needs to be tailored. Minimize this tailoring as much as possible, because tailoring means loss of detail. This tailoring can be minimized or even eliminated by appropriate exposure compensation. But don't panic when you see peaks on the top of the histogram -- not on the left or right. This peak does not refer to clipping, but rather to the fact that this number records a considerable number of pixels. This often happens when you shoot many similar tones.
There is no perfect shape histogram. The shape of the histogram depends on the tone of the image. For example, shoot a grassland full of wild flowers, some flowers are white on the grassland, but you will find that most grasslands are bright and dark green tones, and sometimes there are some black shadows. At this time, the histogram looks like the shape of a mountain. A small part of the tone appears in the white and black areas, while the overall direction is the upward trend in the middle, which represents the main tone in the scene. In Yellowstone Park, try to photograph black objects in the snow, such as a buffalo. Most adjacent tones are either not very bright or very dark. You'll get two histograms of mountains. One mountain represents dark pixels, while the other represents bright pixels. You may see that the middle part of the histogram is empty, but don't be afraid. These vacancies simply represent hue values that do not exist in the image.
Take this buffalo in the snow, and if you expose it correctly, you will get two peaks. One near the right represents snow, the other near the left represents black fur, with almost no peak in the middle.