Is it better to photograph with light than with light, or with light?

In the film age, photographers with a little photographic experience all know the exposure principles of "better than nothing" and "better than nothing" in reverse films. In the digital age, the photosensitive medium has undergone fundamental changes. Whether the previous laws can be applied and what principles should be followed to obtain high-quality pictures have also become controversial. Both "better than nothing" and "better than nothing" have their own supporters. In the past two years, many photographers have deliberately used exposure compensation to reduce exposure when shooting with digital cameras. Generally speaking, more saturated colors can be obtained, and the dark parts can be "pulled out" by curve adjustment of processing software in the later stage. In the past year or so, the popular practice is "exposure to the right", that is, on the histogram of digital camera, the exposure curve is as far as possible to the right. Even if the picture is overexposed, it doesn't matter at most two levels, as long as the bright part doesn't overflow, and then "pull it back" with software later, the picture quality will be better and unaffected.

Let's go back to the movie era. As we know, the principle of developing negative film is to reduce the sensitized silver halide into silver particles by developing solution and keep them on the film, and at the same time wash away the unexposed silver halide to produce a negative image on the film. Therefore, the less exposure, the smaller the density of silver particles, and only the transparent substrate is left without exposure at all, so that images cannot be generated when printing and playing photos.

The process principle of developing reversal film is to wash away the silver particles reduced by photosensitive silver halide during shooting, and then completely expose the unexposed silver halide during shooting (direct exposure or chemical exposure), and then reduce this part of silver halide into silver particles and keep them on the film to form a positive film. Therefore, contrary to the negative film, the more exposure the reverse film is, the smaller the density of the part, and the part that is overexposed beyond the tolerance is basically only the transparent film base.

Then it is not difficult to understand the exposure principle of negative film "better than owe" and negative film "better than owe". The reason is to keep enough density on the film as much as possible, that is, image information. Of course, it can't exceed the maximum density allowed by the film width, and on the contrary, it is difficult to image. But in comparison, if the density is high, it may be remedied by later "thinning". Once there is no density, the darkroom master is helpless.

Although the photosensitive media of digital cameras are different, it is also necessary to record as much image information as possible to get a more realistic image. High-end cameras can shoot RAW format for this.

The photosensitive element of a digital camera consists of many photosensitive points. After each point is exposed, the collected three information will be transmitted to the central processor to calculate the optical density value of the point. The more exposure, the higher the brightness information value and the greater the optical density value. The principle of digital imaging is similar to that of negative film imaging, with high density in bright parts and low density in dark parts. In the later adjustment, to reduce the brightness, you only need to reduce the optical density value of this area in the computer, because this optical density value is obtained from the actual exposure, which is closer to the real image information. When shrinking, it can be relatively "simple and clean", but to improve brightness, it is necessary to increase the optical density value, just like a film without density insists on making images, which needs to be made out of nothing. The computer refers to the brightness information of the surrounding photosensitive points and interpolates and calculates the optical density value. The less brightness information around it, the interpolation.

From this, it is concluded that shooting with a digital camera should not only "rather owe" but also "as much as possible". As long as the exposure histogram does not exceed the right boundary, we can safely overexpose, which will make the picture as clean and delicate as possible. And the higher the sensitivity, the more obvious the effect. Many people should change the habit of trusting only their own eyes or experience and not looking at the histogram when shooting. The digital age has provided us with an intuitive and convenient reference standard. Why not make full use of it? Also, in order to get the most complete image information and facilitate later adjustment, try to shoot in RAW format.

Modern photosensitive media seems to be different, but the digital age of photography experience such as "exposure in the dark, development in the light" proposed by ansel adams is still out of date.

There is also a saying on the Internet that "exposure to the right" is a method based on the imaging principle of digital cameras, which conforms to the imaging characteristics of sensors. This statement points out that digital SLR cameras use 12 bit RAW to record data, and 12 bit RAW can reflect 4096 discrete brightness values. According to this theory, suppose that the dynamic range of a digital SLR is equivalent to five exposures, and the first one (the brightest part) covers 2048 tones. Each gear corresponding to the dynamic range of five exposures will reduce the light by half compared with its previous gear, and the remaining half will be reserved for the next gear. If we don't make good use of the rightmost area of the histogram, we will waste nearly half of the dynamic range of the digital camera. Thomas Noel and Michael Reichman are authoritative supporters of this view. When this view was put forward, digital SLR cameras could only record 12-bit RAW data. Now some cameras have used 14 bit RAW, so the dynamic range occupied by each block will be further expanded.

Although some experts in China think that this view needs to be discussed, it can be seen from the example pictures (not posted in this article) that increasing the exposure on the basis of normal exposure is indeed much larger than reducing the exposure, which seems to be in line with this view.

In short, knowing the exposure law of digital cameras, "owe" or "live" or "stay" or "right" is no longer a problem.