Knowledge about camera photosensitive materials (film cameras)

The photosensitive material of a camera refers to the material that ultimately forms the image of the subject in the camera. Currently, there are films using chemical materials and electronic photosensitive devices CCD and CMOS. Classification of film: a. Classification according to color sensitivity. Color sensitivity: the film’s sensitivity to the spectrum.

Color-blind lenses are only sensitive to blue and purple short-wave light and are slow to respond to other colors of light.

Color separation film, sensitive to blue and purple light, and also has strong sensitivity to yellow and green light. Not sensitive to red.

Panchromatic film, sensitive to the entire visible spectrum. This is what we usually use.

Infrared film is sensitive to infrared rays and can sense invisible light in the infrared region.

b. Classified by image formation

Positive film, the tone and color of the base plate are the same as what you see with your eyes. Also commonly known as reversal films and slides.

For negative film, the tone of the base plate is opposite to what is seen by the eye, and the color is the complementary color of the actual scene (if the original scene is green, then the negative film will be magenta. The original scene is red, and the negative film will be cyan. The original scene is blue, the negative is yellow).

3. Classification by specifications

135 film, the format is 24mmX36mm, 36 sheets per roll, and a few 24 sheets.

120 film, specification is 61mmX81.5mm, can take 12 photos of 60mmX60mm, and 16 photos of 60mmX45mm.

220 film is the same width as 120, twice as long, and can take twice as many pictures.

Loose leaf film, film specially used for large-format cameras. Commonly used specifications are 4X5 inches, 5X7 inches, and 8X10 inches.

Both 120 and 135 films were launched by Kodak. 135 film was launched in 1934 and 120 film in 1901. In recent years, 135 film has been in its heyday. 120 film is rare and mostly used by professional photographers. 220 less. Most films do not have the words "negative" and "reversal film" marked on them, and it goes without saying that they are also negative films.

(3) The logo on the film box

a. Sensitivity

China's GB system and Germany's DIN system are the same: 18 19 21 22 23 24...

American ASA system: 50 64 100 125 160 200...

The current common international standards ISO and Same as America. For example, the sensitivity of ISO100 is twice as slow as ISO200.

The higher the sensitivity, the coarser the grain, and the more obvious the graininess of the photo; the lower the sensitivity, the finer the grain, the more delicate the photo, and the richer the layers (introducing film grain). Under normal light conditions, it is best to choose ISO100 film; when the light is slightly darker, choose ISO200 film; when the light is darker, you should choose ISO400 film.

b. C-41

It is a type of color negative film processing process. Published by Kodak in 1972. Major film factories in the world have their own processing processes, such as Fuji CN-16, Konica CNK-4, Agfa AP-70, Lucky G-70, etc. But currently they are all unified under the Kodak C-41 process. In other words, all color negative films in the world can be processed using the Kodak C-41 process.

In 1986, Kodak announced the C-41B waterless process, and in 1988 it announced the C-41A process, shortening the entire process to 6 minutes and 30 seconds.

c. "Emulsion number" and "Expiration date"

"Emulsion number" is the production batch number of the film. Films with the same emulsion number are exactly the same in terms of photographic performance. There will be slight differences between products. When using in large quantities, it is best to use the same emulsion number to obtain consistent results.

The validity period is generally two years. After the expiration date, the performance will change, such as reduced sensitivity, increased fog, reduced contrast, color cast, etc. In order to reduce emulsion changes, freezing below -18 degrees is the best way. 35mm film should be left for 1.5 hours after being taken out of the refrigerator before use. Take it out from the freezer and leave it for more than 3 hours before using. Room temperature storage is the minimum requirement.

"Avoid high temperatures and develop as soon as possible"

Any film is afraid of high temperatures. Color rolls are more likely to deteriorate than black and white rolls at high temperatures. Kodak color rolls should be stored in a dry environment below 13 degrees Celsius. It is necessary to avoid placing the film near heaters, moisture, radiation, sulfur trioxide, formaldehyde, ammonia, dust, sanitary balls, etc.

"Develop as soon as possible" is because a latent image has been formed on the film after taking the photo. If it is not developed as soon as possible, the latent image will gradually fade, making the original wonderful photos lose their color.

d. "DX"

"DX" is the film data encoding, launched by Kodak in 1981. Most companies in the world currently use this encoding.

"DX" coding mainly includes three types of coding: square, bar and latent image bar codes. The square grid is specially designed for camera perception, the barcode is used for recognition by the automatic developing machine, and the latent image barcode is used for color correction by the enlarging machine.

When buying film, be sure to buy one with a DX code.

e. Inner packaging plastic tube

Most of Japan uses translucent plastic tubes. Kodak, Agfa, and Lucky mostly use black plastic tubes. The function of the plastic tube: tight closing, dustproof, moisture-proof, and harmful gas prevention. After taking pictures, put the film back into the barrel to protect the film from adverse environmental effects.

f. Cassette

The logo on the surface of the cassette is similar to that on the outer packaging carton. Such as trademark brand, manufacturer, film model, number of shots, sensitivity, etc. There are also differences, such as grid codes, bar codes, etc. The film's latitude, sensitivity, number of shots, etc. are all in the grid code. The type of film, manufacturer, processing process, number of shots that can be taken, etc. are in the barcode. (The identification code is omitted).

There is a black velvet cloth stuck to the film feeding port of the cassette, which allows the film to pass smoothly but does not let light enter the cassette. If there is dust on it, it will scratch the film. In order to prevent light from entering, the film leader should not be fully inserted.

g. Film selection

Kodak gold film has extremely fine grain and high color saturation, making it suitable for large-format photos. Fuji Superia has high definition and good color reproduction, and is suitable for mixed light sources. Konica has bright colors, and the blue color online is particularly beautiful, which is called "Konica" blue. Agfa HDC-PLUS has the characteristics of ultra-fine particles and high definition, and won the Best Photography Product Award from 1998 to 1999; Lucky BR100 has greatly improved the resolution and clarity, and is a Domestic imported films that can replace imported products.