What kind of film is called transparent? Talking about the correct meaning of transparency

The word "transparent" has long been regarded as a classic adjective in the photography industry. Whenever a set of films or a piece of equipment can use the word "transparent", it is a supreme honor. But do you understand the true meaning behind these two words? Some people feel that the film is very transparent after polishing it, some people feel that the film is very transparent after increasing the contrast... It can be seen that there are still quite a lot of misunderstandings about the word "transparent". I hope that through the following article It allows people to understand the correct meaning behind the word.

In fact, the popular interpretation of "transparency" in the field of photography should be: fine details, high resolution, and the ability to retain rich details. Next we use a common example to further explain this concept. Underexposed "opaque" image (details in the shadows are missing)

Due to underexposure, the dark details in the photo are missing, and the shadows of the foreground plants are already completely black blocks. The subject's hair and the tree trunks in the distance in the background also lack details and appear as solid black blocks. The left side (shadow part) of the brightness distribution histogram overflows

An overexposed "opaque" image (details in the highlight part are missing)

The dark parts in the photo are rich in details, and the foreground The details of the plants are clearly visible, but the back of the subject, the ground, and the buildings and sky in the distance are all overexposed, showing the entire white color. The right side (highlight portion) of the brightness distribution histogram overflows. A "transparent" image with reasonable exposure

The dark parts in the photo are rich in details, and the shadow parts of the foreground plants also retain enough details. The color transition of the subject is coherent. The only regret is the buildings and sky in the background. There is slight overexposure and a bit of detail is missing. The right side (highlight portion) of the brightness distribution histogram is slightly overflowed.

Through the above diagram, I believe everyone has a certain perceptual understanding of "transparency". Objectively speaking, as long as there is not too much overflow in the shadows and highlights of the photo (neither all black nor all white patches appear), it can theoretically be called "transparent".