How to shoot HDR photography

I believe you should have seen some HDR photos. Maybe you know it's an HDR photo, or you don't know it's made by HDR Technology. Compared with ordinary single exposure photos, HDR photos have more details, richer contrast and more eye-catching pictures.

HDR is called high dynamic range, which means high dynamic range. So what is dynamic range? According to Wikipedia, the dynamic range is the ratio of the maximum value to the minimum value of a variable signal, such as sound or light. It can also be expressed by the logarithm (decibel) with the base of 10 or the logarithm with the base of 2.

Since it is called high dynamic range, natural ordinary photos are relatively "low" dynamic range. Usually, the dynamic range of a camera is only about 14EV, which is far less than the human eye. According to some experts' estimation, the dynamic range of human eyes is at least 20 levels. So the photos taken under some extreme light conditions are very different from those seen by human eyes.

Because HDR pictures have a higher dynamic range than ordinary cameras, but they are shot with the same equipment, we must find ways to expand the dynamic range. Therefore, it is necessary to use a technique called "bracketing exposure". Don't take the word "surround" literally, he doesn't mean that you need to shoot from all angles to surround the scene (because that's how I understood it when I first came into contact with it, so I feel incredible).

Usually, in a large light ratio environment, either the bright part of the scene is normally exposed and the shadow part is dark, or the shadow part of the scene is normally exposed and the bright part is completely overexposed, and even in extreme cases, both exist at the same time. In the peripheral exposure, multiple photos of different exposure value are taken, and the details of the bright and shadow parts of the scene are kept in different photos, and then they are restored to a picture in post-processing. Theoretically, you need two photos, one with highlights and the other with shadows. In fact, a photo with normal exposure is often kept in the camera.

Different brands, different models and different modes of operation, but the principle is the same. Usually, the camera will take three photos around the exposure, and the EV value interval is fixed (called Step in English), which is enough to take HDR photos (for example, take three photos-1EV, 0EV,+1EV or -2EV, 0EV, +2EV). More advanced cameras can take 5, 7 or even 9 exposed photos. At the same time, you can also adjust the interval 1EV, big or small, depending on your personal needs and preferences.

Theoretically, any equipment can be photographed without the limitation of peripheral exposure. But it is always more convenient to choose a good equipment and take better photos. But remember, it's not that you can take good photos by choosing a camera, but that a good camera can help you take better photos, and ultimately it depends on the photographer.

It is recommended to choose an updated SLR camera. SLR cameras usually have excellent image quality and handling. A mirrorless camera is also a good choice. As for the card machine, you can also take exposure. I often take closed exposure photos with Sony's RX 100M2 black card camera, but the camera's step is only 0.7EV and 0.3EV, which is too small.

This is my usual Nikon D800 and Longteng 15-30 F2.8 lens. The high pixel and high latitude of D800 are very helpful for shooting scenery. Longteng 15-30 F2.8 not only has a constant aperture, good image quality, but also is anti-shake, which is very useful for hand-held shooting. Such a set of equipment is very helpful for taking high-quality photos.

Because many photos around the exposure need to be combined into one eventually, it is necessary to ensure that the camera is as stable as possible so that the pictures can overlap. Therefore, it is best to use a tripod to stabilize the camera when shooting HDR, and use wired release to shoot, either wired or wireless. If you don't have a tripod or are not portable enough to carry around, you can also use hand-held photography. If you take HDR photos by hand, because you need more than one continuous shooting, it's best to have anti-shake function on your lens or fuselage, so as to avoid image jitter as much as possible. If not, you can only rely on your iron hand, hold the camera well, try to keep your arm in a stable place and reduce jitter.

Taking HDR photos is also time-sensitive. The lower the angle of the sun, the better the shooting effect of HDR. When the sun is at the highest angle of the day at noon, HDR has little effect. Therefore, according to my shooting experience, the most suitable time to take HDR photos in a day is one hour after sunrise and one hour before sunset.

In these two periods, the angle of the sun is low enough, and the light irradiated at low angle makes the light parallel to the lens as much as possible, which makes the light ratio of the picture in the lens very large, which has exceeded the limit of the light ratio that can be accommodated in the dynamic range of the camera. Therefore, HDR is the most suitable method to improve the dynamic range.

In order to improve the dynamic range as much as possible, it is necessary to let the camera record as many light ratios as possible, so shooting in the direction of the sun is a good choice. This is a bit counterintuitive. In fact, HDR has somewhat broken the traditional shooting method. When shooting at the sun under normal shooting, the sun must be overexposed and most other parts will be underexposed. HDR method can make up for it by surrounding exposure and improving dynamic range.

Now, you can take HDR photos at the right time, at sunrise and sunset. The shooting mode is not much different from ordinary shooting. Aperture priority mode is usually adopted, and the aperture is set according to the scene. So I will focus on the setting of peripheral exposure. Choose the number of frames on the camera and the step of surrounding exposure shooting. If you need to choose continuous shooting mode at the same time, you also need to choose (such as Nikon SLR). You need to read the instructions first to find out where the buttons or menus around the exposure are and how to set them.

Now you can start shooting. Hold the camera steady and use the enclosed exposure mode to shoot continuously. Take three photos with a step size of 2EV as an example. Hold down the shutter continuous shooting, and now you get an underexposed (-2EV), normal (0EV) and overexposed (+2EV) photo. In this way, three HDR originals are obtained for post-processing.

Take it or use a tripod?

Using continuous shooting method to shoot 3 or more photos, it is necessary to ensure that the position of each photo is consistent in post-processing, so it is particularly important to keep the camera stable in the early stage of shooting.

Of course, almost 99% of the hundreds of HDR photos I took were taken by hand. The main reason is that it is fast and convenient to hold, but the problem is that it may be affected by jitter. So try to use the anti-shake function of the lens or fuselage to be as stable as possible. In the post-processing software, the image dislocation caused by slight jitter can be aligned, and the influence can be minimized.

If you don't have an iron hand or are a novice, you'd better shoot with a tripod and release the remote control with a cable. In addition, you can also turn on the pre-lifting function of the reflector, which can also minimize the jitter caused by shutter vibration.

There are many softwares on the market that can make HDR photos. I will take Photomatix, an excellent software for making HDR photos, as an example.

Lightroom is a software that can post-process and manage pictures. Many people import all the photos when they go back, and then import the photos that need HDR from Lightroom into Photomatix. This is a good method. After the Photomatix processing is completed, you can import the completed picture into Lightroom for further processing. Of course, you can also open the photos that need to be processed directly in Photomatix.

Lightbox part

Select a series of HDR photos you took in Lightroom, right-click and select Export → Professional Photos from the pop-up menu. The import settings window of Photomatix will pop up.

In the preprocessing options above, check the aligned images, and check the clipping alignment results on the right to automatically cut the edges of the aligned images, or uncheck to manually cut them. In the drop-down box, you can choose to shoot with tripod or hand-held, which can optimize the program and choose hand-held shooting according to the jitter.

The second line of the Display dialog box has the option of removing ghosting, which allows you to manually set the ghosting phenomenon caused by the displacement or movement of the elements themselves in the screen. You can choose according to whether there are elements with a large moving range in your HDR photos. If so, check it. You can check or uncheck "Reduce Noise" and "Eliminate Color Difference" below, and leave them for later completion in Lightroom.

In the following image processing after HDR processing, check Auto Re-import to Lightrooom Library to automatically import the processed image back for subsequent processing. The rest is selected according to your own preferences, which has no effect on the generated pictures.

Photo mosaic part

When the picture is exported from Lightroom to Photomatrix, if you select the option of eliminating ghosting, Photomatrix will open a window for you to adjust the parameters of eliminating ghosting. Usually, I will choose the option of automatic ghosting at the top left, and then adjust the slider at the bottom to adjust between 0- 100, and judge whether the specific parameters are appropriate according to the picture on the right. Because every scene is different and everyone takes different photos, so this is just an example. The specific adjustment parameters are judged according to your picture effect. Click OK to start HDR processing.

Photomatix remembers the last time the parameter settings were applied to the picture. If it is a series of pictures taken in the same scene, this function will be very convenient, just apply it directly or adjust it slightly. However, if the photos are different, then we need to make specific adjustments to each parameter.

The first part of the adjustment panel is the most basic adjustment of the screen. Intensity is well understood and used to adjust the intensity of HDR effect. Usually I set the intensity higher, about 85- 100. After all, since you are making HDR movies, you must have stronger effects. Color saturation, used to adjust the color saturation of the picture. I usually set it higher, around 70-90, but it's not too high. If it is too high, there is little room for further post-processing in Lightroom or Photoshop, which will be unnatural.

Tone compression, used to adjust the contrast of the whole light and dark part. When it is set to 0, it will not be compressed. When the value to the left becomes smaller and smaller, the contrast between light and dark will be stronger, the highlights will be bright and the shadows will be dark. On the other hand, when the numerical value to the right is larger and larger, the contrast between light and shade is weaker, and the light and shade levels of highlights and shadows are closer, and the overall picture is flatter. When adjusting tone compression, you need to constantly adjust the slider left and right to find the most natural and comfortable parameter value. If the value is too small, don't overflow the highlights and shadows on the screen. It is not appropriate to compare too much.

Detail contrast is responsible for adjusting the contrast of details. The median value is 0. The farther to the left, the smaller the contrast, and the farther to the right, the more stereoscopic the picture will be. The effect of detail contrast is a bit like inverse tone compression, but it affects the picture in different ways. The best way is to constantly adjust the slider and observe the effect.

Lighting adjustment, this parameter will make the photo very dramatic, and it is often easy to be abused, which makes the picture have a strong sense of oppression and makes people gradually dislike HDR photography. Light adjustment is used for the light-dark relationship of different parts of the picture. There is no trick, the key is to constantly adjust the slider to see if the effect is appropriate. When adjusting the lighting effect, we must make the relationship between light and shade in the picture consistent with the relationship between light irradiation, otherwise it will be self-defeating.

At this point, the tone of an HDR photo has been basically determined. The following more option modules can further fine-tune the picture. Smoothing highlights is used to smooth the transition of highlights. Because in HDR photography, the highlight part is easy to break in post-processing, adjusting the smooth highlight slider can effectively repair this phenomenon.

White point, the more to the right, the higher the brightness of the picture. Black dots, the more to the right, the darker the picture brightness. The white field and the black field are adjusted according to the specific situation of the picture. Usually, I only adjust the white field and make relative compensation, while keeping the black field set to 0. The remaining Gamma and temperature (color temperature) can be adjusted without moving, and these two items can be adjusted in Lightroom or Photoshop.

At this point, making HDR photos in Photomatix has been completed. Usually I do further processing in Lightroom or Photoshop. If you feel troublesome, you can finish this part.

Some scenes change very quickly, and there is no time for peripheral exposure, or you didn't remember to make peripheral exposure when you took pictures in the early stage, so you can make HDR photos by taking only one picture. Making HDR for a single picture requires high pre-shooting, and it is necessary to ensure that there are no overexposed or underexposed parts of the picture, so as to avoid the complete loss of details and irretrievable.

However, an HDR photo has its limitations. Due to the limitation of camera tolerance, the effect of single HDR synthesis may not be better than that of the previous lens around the exposed picture. However, as a compromise, a single picture HDR can also produce good results.

Take the single photo you took as the middle value of the HDR processing sequence around the exposure, that is, the one with 0EV. Then adjust the exposure to -2EV and +2EV in Lightroom or Photoshop respectively, and export to 16-bit TIFF format. 16 bits can retain more details than 8 bits, and TIFF format is lossless compression, which is better than JPG format.

In this way, in addition to the original 0EV map, you have three different exposure maps of exposure value. If you like, you can also generate more than five, and the step size can also be set to 1EV or other values. The remaining work is to import into Photomatrix for synthesis, and the steps are the same as those of importing from Lightroom into Photomatrix before.

Now, I not only described the steps of making HDR by taking surrounding exposure pictures, but also described how to make HDR photography through a single sheet. It should be noted that although I take a picture as an example to illustrate, the specific adjustment settings suitable for each picture are different. You can't take an HDR work and adjust it according to my parameters. The most effective and simple way is to look with your eyes, keep dragging the slider, and use your eyes to judge where the parameters are most suitable.

It should also be noted that HDR photos are easily over-processed, very unnatural and even make photos look dirty, which should be avoided as much as possible. It is precisely because HDR is often over-handled that people gradually begin to dislike HDR photos. This is not the fault of technology, but that users have not used it correctly. There is no trick. Only by shooting more and practicing more can we shoot better and better.

Go to the outdoor shooting practice as soon as possible to deepen your impression. I will explain the post-processing tutorial of Lightroom and Photoshop later.