Reverse film is a kind of photographic film, the use is similar to the ordinary negative film (exposure should not be too much), the color of the reverse film on the negative is the actual color. It is much better than negative film in brightness and clarity, and it is also very good in color, so photography professionals use reverse films. The main feature of reverse film negative impact is the contrast of cold and warm tones in the picture. The saturation of the bright area is increased, showing a warm tone but not exaggerated, and the dark area has a significant tonal shift. This is a relatively popular online Photoshop means. \"Negative effect\" this special effect is mainly through the separation of light and dark details of digital photos, independent calculation, to obtain a relatively wide dynamic range of photos. And the loss of detail is minimized. Therefore, it is also called \"high tolerance negative film effect\". This function has been improved several times on the basis of the original, the color reduction is better, the contrast and contrast are simulated according to the characteristics of the negative film, the effect has been close to the composite image of multiple exposure. The main feature of the negative film effect is to compress the histogram from the two ends to the middle, similar to reducing the contrast and increasing the tolerance.