Analogic photograph

Machines and tools of traditional photography.

Analogue photography, roll or reel photography, also known as traditional photography, b>silver or chemistry, is the retronym used to describe the traditional photographic process, which uses non-digital techniques to produce images, in comparison with digital photography —of appearance more recent-. Additionally, this term also serves to separate the photography that uses film rolls, chemical substances and photography darkrooms using techniques corresponding to the 19th century and the first half of the 20th century, which can be identified as alternative photography. It is usually based on a physicochemical process that involves the use of an active photosensitive material —applied on glass plates or on a flexible film of translucent material, currently plastic— and its stabilization —developed—, to obtain and process the images. images.

Traditional photography has formed an important body of knowledge that includes the correct handling of film and paper sensitivity degrees, the handling of a wide variety of lenses, filters and light sources, and the skill or care of temperatures, concentrations and usage times with developer and fixer liquids. Of all this there are tables, formulas and recipes with numbers, volumes, temperatures, times and scales.

Process

Photographic film

Reel in camera

To obtain photographic images, a support known as photographic film is used, where the light-sensitive element is silver halide, which is the active compound present in the photographic emulsion; This, in turn, is a colloid in suspension, on a very pure gelatin base. The size and number of silver halide crystals determine the film's sensitivity, also known as speed —a term that can be confused with shutter speed—, which is normalized and expressed on a photographic sensitivity scale standardized by the ISO. When the shutter is opened for a brief moment, the light that passes through the lens falls on the film, leaving the impression of the image on it, which at this point is called the latent image; it will decompose from that moment on, until it is revealed. In reality, the light initiates a physicochemical process, producing a point of sensitivity in the compound, thus obtaining a latent image, which in the end, when the film is immersed in the developer, through a reduction-oxidation process, will occur. the decomposition of the halide into black metallic silver, thus obtaining a visible image.

Getting the image

For a given film, of a certain sensitivity — ISO 100, ISO 200, ISO 400 — a certain amount of light is needed to get the correct exposure. This quantity is called EV —in English, Exposure Value—. The higher the sensitivity, the less light you need. Thus, for example, with 6400 ISO films, forcing them to 60,000 ISO allows you to photograph a black person inside a sack inside a poorly lit tunnel. While 25 ISO films allow you to take pictures of the sun's surface without burning the film.

To obtain the correct EV, cameras consist of a diaphragm and a shutter. To make an analogy between the eye and a camera:

• Diaphragm: It is the iris of the eye. Opening more or less, we get a certain amount of light.
• Obturator: It is the eyelid. Having it more or less open time, we get a greater or lesser incidence of light in the movie.
• Objective: It is the crystalline. It is responsible for focusing the view, so that the objects are sharp in the film
• Movie: It's the retina. Where the images remain latent until the film is revealed.

Using an exposure meter, the EV needed for that film is measured. Let's say it gives a speed of 1/500 and aperture 4. That EV is equivalent to speed up and stop down, or speed down and stop up. The speed is usually expressed in 1 s; and the diaphragm in "f" or fractions of diameter.

Speed	Diaphragm f{displaystyle f}
1/500 s	4
1/250 s	5.6
1/1000 s	2.8

All of these values are the same EV for a given amount of light. Therefore, we can choose any combination of these to obtain a correct exposure. Depending on what we want to get. If we want the sharp field to be greater, we will put a larger diaphragm —5.6 f gives a greater depth of sharp field than 2.8 f— or if we want to freeze the moment, we will put a higher speed —1/1000 s freezes the image more than 1/250 s—.

There has been some talk about "forcing" the film. Forcing the film is a procedure by which we use a film of a certain sensitivity at a much higher sensitivity. To do this, we set the sensitivity in the camera to the sensitivity that we want to use, and we shoot the camera calmly. When developing, this sensitivity must be compensated by increasing the developer temperature. For this, we will have to be the ones who reveal the reels, since in developing shops, the entire process is mechanized and the film will not be forced.

Revealed

Negative

The development process consists of two basic steps: development and fixing, which in turn are divided into intermediate steps depending on the type of film to be treated. The image thus obtained has its light values inverted with respect to the original capture, which is why the treated film is known as a negative.

Once dry, copies of the image can be made from this film or "negative" on paper or on another film, in which case we will obtain a translucent slide or positive, which will allow us to observe the photograph by projection or transparency. The images obtained, by inverting the light values again, by magnification or contact, give us a "positive" result. This process is called positive.

If we use a specially treated film in the camera, for slides, we will obtain the images directly in positive when developing the film.

Formats

The most popular chemical film format is 35mm film, also known as 135 film, used in most SLRs and compact cameras until the end of the 20th century. After said format, the most popular are the medium format —120, 220—, Polaroid —instant development—, and the large formats —4x5 inches, 5×7 inches and 8×10 inches mainly—. The last format to appear was Advanced Photo System —better known by its acronym, APS—; That allowed you to expose your film in C / H / P formats. Although possibly the least popular of all formats and yet its dimensions were used as the basis for the first sensors in digital photography. SLR until its evolution to Full Frame.

Advantages and disadvantages

Main article: Film vs. Digital

Advantages

• The time and expense of film photography inculcate handicrafts and patience.
• Depending on the sensitivity of the film you can get a wide range of dynamism.
• A printed image (not editable) can help as legal evidence of the photographed subject.
• In optimal processing and storage conditions, a film can last forever.

Disadvantages

• Film photography needs more time and skill than digital photography.
• The film is delicate and needs careful treatment, cooling, sun protection, dust protection, etc.
• The film may suffer a deterior, such as the photographs are clouded.
• Film processing has a high economic cost. Sometimes you have to find a lab and you have to expand or scan.