آلية ضبط الاضاءة في الكاميرا .. كتاب طبع وتحميض الصور الفوتوغرافية

The mechanism for adjusting the lighting in the camera:

We said earlier that one of the main goals of the camera is to adjust the amount of light reaching the film slide. In order for the film to be properly exposed, a calculated amount of light must enter it, and any increase or decrease in this amount will damage the formed image. For this reason, the camera is provided with a special mechanism to adjust the amount of light entering the film slide with each press of the shutter release button. This mechanism consists of the lens aperture and the shutter.

Simply an adjustable opening through which light passes before it reaches the film. The amount of light entering the film is controlled by adjusting this aperture, either by increasing its width in order to allow more light to enter, or by narrowing it. These openings are indicated by the letter /f// and numbers such as 8-11-22-etc. lens aperture is
1/28 1/56

F-22 is the larger the number, the narrower the aperture of the lens, and vice versa. The aperture of the lens is much smaller than the aperture of the f-8.2 lens, and therefore it allows only a little light to pass through it. The aperture also contributes to controlling the depth of field. We will leave detailing depth of field to a later chapter. The shutter can be thought of as a thick curtain inside the camera that allows light to pass through if it is lifted. When the curtain is raised for one second, much more light enters the camera than if it was raised for 1/125 second, for example. Thus, we find that we can control the light falling on the film slide by one of these two means. If we find, for example, that it is necessary to increase the amount of light falling on the film slide, we can either adjust the shutter so that it remains open for a longer period, or adjust the lens aperture to a smaller aperture.

- Note that the largest aperture on the far right is indicated by the smallest number and the smallest aperture on the far left is indicated by the largest f-number.

the film :

It is a transparent, plastic layer coated on one end with a layer of gelatin containing micro-particles that are sensitive to light. That is, its chemical nature changes when exposed to light. The presented film is called the negative because the bright parts of the photographic subject appear black on it, while the black parts of it appear in transparent and gradient colors in its transparency. And the subject that we photographed appears naturally, that is, the dark places in the original subject appear dark in the image, and the light places in the subject appear light in the image.

Film sensitivity:

All photographic film, apart from some very special exceptions, is sensitive to light. The degree of sensitivity varies according to its type and purpose. The sensitivity of the film is generally measured in ASA. For example, the 125 aza film needs more light than the 400 aza film, because the 125 aza film is considered less sensitive to light than the 400 aza film. Thus, we come to a conclusion: 1- We use a smaller aperture with a faster film that is “more sensitive to light.” As for the slower film that is less sensitive to light, it needs a larger aperture. 2- We use a faster shutter speed with a fast movie, but a slow movie needs a slow shutter speed to increase the amount of light falling on it. 3 - Quick Film is useful in low-light situations, such as indoor photography

the rooms . The relationship between film velocity and granules (growing). C

It means fast. Large granulation of fast film B Granulation of medium speed film. However, this does not mean that we ignore the slow film and always resort to using a film. The greater the sensitivity of the film (i.e. its speed to light), the more negatively this will be reflected on the quality of the image. More precisely, we say that the chemical crystals in the fast film are larger in diameter than in the slow film, and this leads to their appearance in The final print is in the form of small dots, thus forming a blurry image or blurred contrast. This technical error becomes more exacerbated when the image is enlarged to large prints. The small dots then appear more clearly. For all this, we must avoid using fast films except in cases of extreme necessity when it is not There is no way for us to obtain the image except by using a quick film

Fine granulation, slow film


This is due to poor lighting conditions. The typical negative is one that contains clear details, and the reason for the details is largely due to the speed of the film used. It should also be good in contrast. In order to bring the expression of contrast to mind, imagine that you took a picture of a scene that contains very bright places and other very dark places, and that it also contains places that range between the two previous values, such as color gradations and clarity of gray.

When this negative appears, it must contain all the previous white, gray and black light values, to be said to be a typical negative light contrast.

dense tuberculosis

normal negative

thin negative.

But sometimes it happens that the human eye overestimates the amount of lighting needed, so the result is that we get a negative less than what is considered ideal. This error is embodied either in the form of an underexposed negative “thin or an overexposed negative that is dense and in both cases we did not get a normal negative” or an ideal one. The result will still be substandard unless we make some compensation during the printing process. It is worth noting that errors of non-contrast can be caused by a wrong endorsement. Therefore, it is recommended to use a light meter separate from the type camera

The one who holds the hand in order to ensure obtaining a correct contrast, and adherence to the specified endorsement times completely. We do not talk about the sensitivity of the film without referring to a procedure that many professionals and amateurs resort to sometimes, which is called pushing acidification, and the definition push is to treat the film as if it has a higher sensitivity than it is in reality. For example, shooting with a 400x1 film as if it were a 1200x1 film and endorsing it on this basis. To endorse a film in this way, you must increase the endorsement time or use a special appearance for the payment process. And our previous example requires the use of an appearance such as Acufine Developer. At first glance, it seems that it is easy to push any slow motion movie to get the details in the subject. Perhaps the lighting conditions were poor during filming. But remember that the details that were not recorded on the film, we cannot in any way send it again. Also, the pushing process affects the degree of clarity in the final print due to the increase in the grainy appearance, the graininess in the film, and the increase in light contrast that we obtained in an unusual way. Therefore, it is advisable not to resort to paying the film except when there is an urgent need for that, such as our presence in poor lighting conditions with slow sensitivity film, and not filming means wasting the opportunity for us. event before us

Principles of endorsement of black and white film:

When the film is exposed to light, the chemical granules in it are affected according to the amount and intensity of the light they receive. Change the lens aperture on the camera. The exposed film is first placed in the “Developer” mode, which transforms the areas that were exposed to light into different degrees of darkness, leaving the areas that were not exposed to light relatively transparent. In order to stop the appearance on the film after the completion of the endorsement process, the film is placed in a stop bath solution, and finally the film is placed in a fixer solution that works to strengthen the film’s rigidity and make the images recorded on the negative page fixed features.

This is, in short, what we mean by film development. In the remainder of this chapter and in the next chapter, we will deal with chemicals
Equipment and techniques required for film endorsement. And you will discover for yourself that endorsing the film is an easy process that you can do simply after that. Apparently, you have to buy acidification equipment from any store that sells photographic equipment. The endowment bath can be replaced with plain water or plain water to which a few drops of acetic acid are added.

You also need:

1 - Scissors
2 - Kazooze bottle opener

3- endorsement vessel (tank)

4 - a photographic thermometer e - dark colored bottles for storing chemicals 4 or
5 - a soft brush
6 - funnel;
7 - press studs
9- Envelopes for storing films