Teach you how to get the best exposure

Introduction: Correct exposure is critical to taking excellent natural photography images. Proper exposure should avoid overexposed highlights, have minimal noise in dark areas, and capture enough light in the pixels to ensure accurate color reproduction. The camera's metering function, lens aperture and shutter speed all determine the final exposure. However, many times, the camera needs help to get the best exposure, so you'll want to learn these methods.

Fortunately, exposure control with digital cameras is much easier than exposure control with reversal film. Digital cameras allow you to see the image instantly so you can tell whether the exposure is correct or not using highlight warnings and histograms. You don't have to think twice about whether your exposure is off the mark because highlight warnings and histograms show it for you. Although exposure is easy to control with a digital camera, it will still be helpful to master the basic guidelines of exposure. It's necessary to understand aperture, shutter speed, and how they work together. It's also important to know the pros and cons of different metering modes. You have to learn why some objects require exposure compensation and how to do it.

Digital exposure requires you to retain details in most highlights (the exception is metal reflections that have no details) and also retain details in dark areas. The dynamic range between light and dark can be fully recorded by digital sensors. There are about 6 stops of aperture. Digital exposure can be displayed instantly with highlight warnings and histograms, so when shooting still life it's easy to adjust the exposure until you get a picture you think is accurate. You can even use a range of different exposure values, especially in difficult situations, and then delete the ones that don't have value. Both JPEG and RAW format digital images can be optimized by improving exposure through post-processing software, but they are not perfect.

1. RAW format and JPEG format images

Before discussing exposure in detail, it is important to understand which image file format you plan to use, because under appropriate exposure, both have the same Slightly different. Two common file formats are: JPEG and RAW. JPEG format images are a lossy file format provided by the camera to obtain sharpness, saturation, white balance, contrast, and color gamut. RAW format files are unprocessed data passed through the sensor and are 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, Fujifilm uses .RAF format, and other cameras also have different formats. A RAW format file must be converted by software to obtain the best quality.

There is considerable debate as to which format is best. This debate is interesting, but there is no right answer. A photo can be used in both formats. Before we decide which format to use, let’s take a look at their advantages and disadvantages.

Advantages of JPEG

? JPEG images are processed directly by the camera, so you can save time.

? They take up less storage space.

? The camera buffer clears quickly, so you can keep shooting.

? JPEG files are smaller than RAW files, and the maximum continuous shooting speed is much higher, making it suitable for sports photography.

Disadvantages of JPEG

? There will be data loss when JPEG is first generated, and this will happen every time it is stored in the future.

? The 8-bit rate data limit of the JPEG format can cause color separation. This means that you can lose continuous tones and cause image banding, especially if you use a lot of software to edit the image.

? Process parameters such as color space, white balance, contrast, exposure, hue and sharpness are all locked in the file, which will reduce your ability to adjust in the software later.

Advantages of RAW

Since these files contain unprocessed raw data from the sensor, the white balance, sharpness, contrast, color space, saturation and Great control over exposure.

? The RAW format file is much larger than the 8-bit rate data of JPEG, which has more advantages in optimizing the picture in the later stage (without losing the sustained tone).

? The RAW format converter has excellent adjustment functions in terms of noise control and lens correction.

Disadvantages of RAW

Large files can quickly fill up the memory card.

? The number of pictures taken continuously at one time is greatly reduced.

? It must go through a RAW file converter, so it is very 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, then high-quality JPEG is the best choice.

Of course, you want to make sure you're exposing it correctly and have the right white balance, because once the shot is taken, it can be difficult to adjust in post. Many cameras offer you a variety of JPEG formats to choose from, and it's best to choose the highest quality one. If you want to use a low-quality JPEG image for the web, it's very simple to convert from high quality to the image size you need. If you love computer post-production and want to produce large images with the best quality possible, then shoot directly to 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 capture friends' gatherings and things that don't require the highest image quality, and we intend to give the photos away to people at any time. For serious nature photography, we only shoot RAW format images. Take tons of pictures, edit them aggressively, and keep only the best. I'm in no way implying that professional photographers don't shoot JPEG images. Professional sports photographers mainly shoot JPEG files because they need to use images quickly within deadlines, and the high speed of reading JPEG files will help capture exciting action moments.

Two reticulated giraffes casually put their heads together. The interaction between wild animals often provides us with the opportunity to take excellent pictures.

3. Correct exposure of JPEG files

When shooting JPEG files, you really need to ensure perfect exposure. Due to the smaller recording depth, shooting JPEG images brighter or darker can cause various problems, such as losing continuous tones. If possible, avoid clipping the left and right sides of the histogram. In most scenes, it is best to start from the right side of the histogram and approach the right side. It does not necessarily have to be placed on the right edge, but it is hoped that the image data will be recorded in the area to the right of the center of the histogram. If the contrast in the scene is very strong and cropping cannot be avoided, then crop the left side of the image or the black part of the histogram and try to retain the detail level of the highlights on the right side.

For digital photographers, it was important to preserve the detail of this trumpeter swan's white feathers. Make sure the histogram data is close to the right but not clipped.

4. Correct exposure of RAW images

Unlike JPEG images that require correct exposure when shooting, RAW files have huge latitude for adjusting exposure. Through the software, you can adjust the exposure to no more than 1 stop of overexposure or 2 stops of underexposure. In essence, RAW files are like film negatives, and through software adjustments, the exposure can be almost (within a certain range) as perfect as if it were back on set.

Although RAW files can be optimized for exposure, this still takes time and may result in a certain loss of quality. There is another way to get the best exposure for RAW files. Using a histogram, it's easy to know if your exposure is perfect. Your goal is to have the data recorded on the right side of the histogram, without touching the right edge as much as possible. The curve on the right edge is called blown out highlights and shows little or no pixel detail due to overexposure. If a pixel doesn't register detail, there's no way to make it reproduce it.

Similarly, try to avoid having the histogram curve concentrated on the left side. Obviously, if you take a picture that has completely black areas, then they will be represented by pixels concentrated to the left of the histogram. For most images, you should keep the histogram starting from the part on the right without blown highlights and ending close to the left edge. The exposure method for RAW file images is often referred to as "exposing to the right." Using this method of exposure will give you great flexibility and maximum detail in your RAW digital file images. When you reduce digital image noise and improve the signal-to-noise ratio in this way, the sensor measures light more accurately.

I could talk a lot about noise and signal-to-noise ratio, but if the RAW image you shoot is close to the right side of the histogram and there are no highlights that require cropping of any details, you really don’t need to know. These.

5. Help you get the best exposure

Histogram

Histogram is the key to determining whether you get the best exposure. A histogram may be difficult to understand at first glance, but it is actually a very simple histogram of exposure data, a graphical representation of exposure. This picture has a 256-level gray scale along the horizontal axis, ranging from 0, which is pure black at the far left, to 255, which is pure white at the far right. The vertical axis represents the pixel value for each brightness level among the 256 levels.

If the image is overexposed, you will see a peak on the far right side of the histogram. This peak represents those pixels being overexposed. In general avoid overexposed pixels as they record little to no detail. However, specular reflections like metal or water will have no detail whatsoever, so it's okay to take pictures of these materials with a small peak on the right side of the histogram.

Also try to avoid peaks appearing on the far left side of the histogram. Such peaks also mean that the pixels are not recording details because the light is too dark so the pixels are not recording much light data.

However, there will also be a peak on the far left when there are deep blacks or shadows in the scene. Post-production software can adjust exposure by brightening or darkening, but if there are many dark pixels, it will lead to digital noise, that is, these pixels have unexpected color spots or brightness values ??compared to adjacent pixels.

The pixel peaks at the far left or right end of the histogram are often called faults and need to be clipped. Minimize this cropping as much as possible, as cropping means loss of detail. This clipping can be minimized or even eliminated completely with appropriate exposure compensation. But when you see peaks at the top of the histogram - not on the left or right side, don't panic. This peak does not refer to clipping, just that this value records quite a few pixels. This often happens when you shoot a lot of similar tones.

Histogram shape

There is no perfectly shaped histogram. The histogram shape depends on the tones that make up the image. For example, if you take a picture of a meadow full of wild flowers, some of the flowers on the meadow are white, but you will find that most of the meadow is light and dark green, with some black shadows occasionally. At this time, the histogram looks like the shape of a mountain range, with a small number of tones appearing in the white and black areas, and the overall trend is an upward graphic trend concentrated in the middle, which represents the main tones in the scene.

In Yellowstone, try photographing a dark object in the snow, such as a bison. Most adjacent tones are either very light or very dark. You will get a histogram shaped like two mountains. One mountain represents dark pixels, while the other represents light pixels. You may see gaps in the middle of the histogram, but don't be afraid. These gaps simply represent tonal values ??that are not present in the image.

Shooting this bison in the snow, if you expose it correctly, you will get two peaks in the data. One of them near the right represents white snow, the other near the left represents black fur, with barely a peak in the middle.