About the film

The charm of film photography lies in its texture and attitude, and it has a great sense of participation and creativity.

Its intention and serious attitude towards photography are beyond the reach of digital photography at the beginning.

The following is my own little knowledge about film photography.

Some still need to consult and learn from you, thank you. :)

1 film principle

Black and white film photography is based on the photosensitive principle of silver halide (silver iodide, silver bromide, etc.). ). The top layer of the film is a silver halide coating containing gelatin.

When silver bromide is irradiated by light, silver bromide is decomposed into ions, and then contacted with reducing agent, and part of silver ions will be reduced to silver atoms and gathered on the surface of silver halide crystal. The stronger the light, the more silver bromide decomposition. As long as five silver ions are accumulated on the surface of silver halide crystal, a stable latent image is formed, which is enough to make silver bromide crystal sensitive to reducing agent (developer).

When developing a negative film, a redox reaction will occur, and the exposed silver bromide will be reduced to neutral silver atoms, forming tiny silver nuclei, leaving an opaque image on the film.

Color film is more complicated than black and white film, but the principle is similar. Generally, the three-layer superposition is made of silver halide and three-color latex paint.

About preservation: the image of black-and-white negative is composed of stable metallic silver particles, which will not change with time. Although gelatin is sensitive to humidity and temperature, black and white negatives can be preserved for hundreds of years if they are well preserved.

Color negative is much more vulnerable. Due to the instability of various dyes, they are more sensitive to the environment. For example, cyan dyes fade more easily, so color negative will appear red after a long time. In addition, the ultraviolet rays in the sun will make the magenta dye fade.

Two different frames of film

135 framework

Because its width is 35mm, it is also called "35mm film". The film has holes on both sides and is packed in a box. The standard imaging area of 135 film is 24 mm x 36 mm, and there are four kinds of pictures that can be taken in each roll, 36, 24, 20 and 12. A camera using 135 film is called a 135 camera or a 35mm camera.

Medium format

The medium format is much larger than the 35mm roll, which requires a special camera. The imaging quality of medium format film is better than that of 35mm film, so it is used by many professional photographers. There are two kinds of films: 120 and 220. The average medium format camera can use 120 roll, because there is lining paper in the roll. 220 rolls are not like this, only some models can be used, but because there is no lining paper, the reel can hold more films, about twice as much.

The width of 120 film is 6 1.5mm, and there is no cassette packaging, but there is backing paper. Usually mounted on a mandrel and protected with paper to prevent light leakage. A camera that uses 120 film is called a 120 camera. The width of 220 film is 6 1.5mm, and the length is twice that of 120 film. There is no backing paper, but there are protective papers at the beginning and end.

220 film cameras are rarely used now, and most of them use 220 film by replacing the back of 220 on 120 cameras.

120/220 film has various nominal imaging areas (length in cm):

6 x 4.5: 645 for short, and the actual imaging area is 56 mm x 41.5 mm; ; 120 can be shot 16/ 15;

Short for 6× 6: 6× 6, the actual imaging area is 56 mm× 56 mm; ; 120 can be shot 12;

The abbreviation is 6 x 7: 6x7, and the actual imaging area is 56x 70mm；; 120 film can be shot10/9;

6 x 8: the actual imaging area is 56 x 76mm；; ; 120 film can take 9 shots;

6 x 9: the actual imaging area is 56 x 82.6mm；; ; 120 film can take 8 shots.

Large format

Large format film is slightly different from 35mm and medium format film, because the film appears in the form of 4 ′× 5 ′ (or larger) sheets and must be put into the film holder. The loading process must be carried out in the dark. Only two photos can be put on each bracket. The pockets of traditional photographic vests are designed for this kind of large-format film. There must be many pockets for so many film clips.

Three different types of movies

Reversing plate) chromium:

Color reversal film is a kind of film that can directly obtain color transparent positive film after reversal development. A negative image is formed in the first stage of development, and then a positive image is formed with color dyes. Color reversal film can directly project the image onto the screen with a slide projector, which can not only print and play photos directly, but also be used as the original film for color separation and plate making printing. The color reversal film is truly saturated, and the clarity and sharpness of the image are relatively high. However, compared with color negative film, the exposure latitude is narrow, slightly insufficient or excessive, which will affect the imaging quality. Therefore, it needs to be very accurate to shoot the reverse film. The color reversal film ends with krom. The special effect of negative film can also be obtained without backwashing.

Reverse film is a negative film at the beginning of development, and it becomes a positive film after being exposed halfway and developed again. So development is also different from negative film. E-6 process is used for reverse film, and C-4 1 process is used for negative film. Brightness and clarity are much better than negative films, and the colors are excellent. Negative film development of reversal film is to shoot with reversal film and develop the film with C-4 1 to turn the original reversal film into negative film. The photos obtained by negative film reversal are bright in color and contrast, and the red, blue and Huang San colors of the scenery are particularly exaggerated; Objectively speaking, the negative effect of reverse film is more expressive in color than negative film, and the exaggerated expression of its tone is not as good as that of color negative film, but in hierarchical expression, the negative effect of reverse film is not as good as negative film, so it is very important to determine the shooting subject first and then choose the film type.

Positive film:

After the negative film taken by the film camera is developed and edited, several copy tapes (the original film is very precious) are copied first, and then corrected with the positive film, and then it can be shown in the cinema. Positive film is a general term for photosensitive film used to print photos, slides and film copies. It can print the negative film on the negative film into a positive film, so that the brightness or color of the image is the same as that of the subject.

Some people mistakenly call reverse films positive, which is wrong. The image on the positive film is usually copied from the negative film, and the negative film is taken directly with the camera. The biggest difference between positive film and negative film is that positive film is a positive image obtained after "transfer-development" of other negative films; The reverse film directly obtains the positive image through its own "shooting-developing". Positive film is similar to photographic paper. The matrix of photographic paper is opaque paper, and the matrix of positive film is transparent polyester fiber and acetate fiber. The exposure data used in the use of reversal film must be correct, otherwise it will be irreparable; Using negative film, as long as the exposed data does not exceed the width of the film, color correction can be carried out by amplification or amplification.

Negative film (negative film)

In other words, our common film is an image obtained after exposure and development. Its brightness is opposite to that of the main body, and its color is the complementary color of the main body. It needs to be printed on a photo to be restored to a positive film. To put it simply, after the film we shot is developed, the image we see is a reverse color image, and then it becomes an image with the same color as the scene we shot by enlarging or enlarging it into a photo. Make a black and white movie. On the negative, human hair is white. In fact, white clothes are black on the film. Color film, the color on the film is only complementary to the actual color of the scene, for example, clothes that are actually red are green on the film. Negative film, whether black and white or color, is the most commonly used film for photography. We usually take pictures with ordinary cameras and develop negative films.

4 Sensitivity and graininess

Whether you choose black-and-white film or color film, you need to consider the sensitivity and granularity of the film and the relationship between them.

The sensitivity of film refers to the sensitivity of photosensitive materials to light, also known as film speed. Film sensitive to light, such as film with sensitivity greater than 400, is called fast film. On the contrary, films that react slowly to light, such as films with a sensitivity lower than 50, are called slow films. Generally, films with sensitivity 100 ~ 200 degrees are called medium-speed films. The sensitivity of the film is provided by the film manufacturer. There was no uniform label in other countries before. In 1980, the international standard sensitivity is implemented. It is based on ASA system used in America and d in system in Germany. The symbol is ISO, written as ISO 100/2 1, with 100 in front being the ISO(ASA) value and 2650 behind.

Generally, high-speed film needs less exposure and is suitable for shooting high-speed moving objects, such as sports, in low light. However, the graininess of high-speed film is relatively coarse, not as fine as that of low-speed film, and the enlarged photos after developing photos with it appear coarse graininess and lack of detailed texture.

If you want to take photos with high magnification, rich details and fine particles, you can choose a slow film with a sensitivity below 50. Slow-speed movies can sometimes use slow shutters to display dynamic effects. Compared with the past, the graininess of the film has been greatly improved. The quality of films between ISO100 and 400 is good, which can be applied to almost all kinds of occasions and shooting conditions.

PS:

Film brand: Heismann Kodak, fujifilm,

KONICA, Agfa, Le Kai.

5 Sixteen Rules of Sunshine

The sun is sixteen clouds and eleven.

Cloudy, with eight dark clouds, 5: 6.

Take four pictures at dusk.

Snow falls on rainy days at dusk.

The shadows are clear, the sun is shining, the clouds are light and the wind is light.

The vague figure is turbid.

Dark clouds covered the tracks.

At sunset, the sun sets in the west.

Steps:

Step 1: Set the shutter to the sensitivity. For example, ISO 50 sets the shutter to 1/60 and ISO 65438 sets the shutter to1125. In short, make the shutter speed as close to the sensitivity as possible.

Step 2: Set the aperture to f 16 on sunny days, f 1 1 on cloudy days, f8 on cloudy days, and f5.6 on very cloudy days.

How to distinguish the degree of cloudy sky? You can tell by observing the shadows. If the shadow is clear but the edge is a little blurred, it is "slightly cloudy", if the shadow is not clear but still visible, it is "overcast", and if there is no shadow, it is "very gloomy".