دراسة مفصلة وعملية للتبرغل من أجل الحصول على نعومة أكثر .. مجلة فن التصوير اللبنانية

Detailed and practical study of granulation in order to obtain more smoothness

Fine-graining or pointillization is an issue that attracts more controversy whenever the subject of photography is brought up on the rug for research, and this issue will remain controversial because it is difficult to resolve the debate about it, but the issue of its control remains within the reach of the serious photographer who is looking for higher accuracy in his work.

In all clubs, classes and trade publications, long discussions are repeated on the subject of percolation, whether dripping on
Indeed, we have read in the majority of photographic publications that silver dotting of medium scales on a negative or photographic print is much smaller than to be seen without
under a microscope.

What are these discussions about, and what can be done to control it? ..
Let's go back to basics, and look at how movies work.

Silver crystals:
The structure of the basic granulation of a film is decided during the making of this film, so that we can control that to some extent, but the basic structure remains unchanged. What is meant in essence is the speed of the film - to get faster films, the presence of larger crystals of silver halide is necessary. Heating silver halides and gelatin in one solution together, and the heat concerned encourages the growth of crystals and decides the issue of their distribution in the holder.
gelatinous This process, which is known as “curing (0), determines the final characteristics of the film, its optical contrast, speed, and grain structure. Regardless of the speed of the film, we have to remember that not all silver halide points are of the same scale. Since the larger dripping points are much more sensitive than the smaller ones, the speed of the film depends in its simplest form on the number and distribution of the larger points. The drop scale is large, but with fine, fine dotting films, this is possible, as the drop scale field is kept small, and the points themselves are kept small.

Since the smaller dots are the least sensitive, micrograin films tend to have a low velocity sensitive layer.
The range of different grain sizes also affects the optical contrast - the wider the field, the lower the optical contrast - and thus the fine grain films tend to have a very large noise contrast and a slow sensitive layer, while the fast films tend to have low optical contrast and a large grain size.
And as long as we said at the beginning that the scale of each individual point is too small to be seen with the naked eye - even with fast movies - then what are we watching? ..
There are no separate points, but rather the collective effect of dripping.

The thickness of the sensitive layer:
There is another issue linking the grain with the photographic effect of the film. So that the main feature that determines the granulation of the film is the thickness of the sensitive layer. What we see is not a single layer of silver dots with gelatinous spaces between them, but a “sandwich of several layers, and what the thickness of the sensitive layer means is that the deeper the sensitive layer is, the more layers of silver halide crystals are within that thickness. If it is possible By producing a film with a single, very thin sensitive layer, what we get is an image that is almost grain-free, as the individual dots are very fine.
Let's go back to the commercially produced film. The fact that there are a number of layers means that individual fine points overlapping with each other have that optical effect that brings them together into one large point, and the greater the size of the individual points, the greater the possibility of this optical aggregation. In addition to this, with the presence of large points, and between them a kind of mutual attraction - the probability of actual agglomeration increases instead of the occurrence of the visual effect for that only, and if the growth of the points during the endorsement is allowed to aggravate, then the spaces between the points will diminish to the smallest extent, and the result will be large and clear points .

Then, since the thickness of the sensitive layer determines the number of light-sensitive silver halide crystals in a specific area, the thickness of the film will play a major role in determining the speed of the film in association with the crystallography scale.

In addition to this, the thickness of the sensitive layer controls the sharpness of the protrusion in the image as well, and it controls the optical contrast to a certain extent. Also, the thick sensitive layers suffer from radiation (*)) as the scattering of light within the sensitive layer increases the decrease in the sharpness of the highlights and the optical contrast together.
From here, the thickness of the sensitive layer and the two results that emanate from it become matters that should be taken into account, as long as it itself plays an important role in determining the level of graininess in the final image.

Available light:
If the image itself is low-resolved (*) out of focus or not sharp, the easiest thing to focus on during printing is the grainy structure. And because the edge of the graining is sharper in prominence and is subject to dissolution more easily on the print than on the image itself, which makes the graining much more prominent in the final print. This can be said of any image with fairly low resolution, and if that lack of sharpness is caused by the thickness of the photosensitive layer and irradiation, or by poor resolution by the camera lens, the result will be the same.
In practical terms, this means that the way we tend to photograph at low noise levels is also likely to increase the graininess that appears in our images, regardless of the quality of the lens. The use of high speed film is often to be avoided, except in conditions of very low light levels. It is likely that these very low light levels will dictate the way we use the camera, at least in part, as it will require wide apertures to allow a usable shutter speed. Since such a wide aperture forces the depth of field to be shallow, it is inevitable that there will be large areas within the image frame that are out of focus, and just as with a poor resolution lens, what the area that lacks sharpness means is that the grain will be the easiest thing to do. watching .

Exposure is also a factor that controls the overall sharpness and clarity of the final image, as it affects the overall effect of exposure. Indirect control of the permeation structure.
It should be noted here that the resolution of the photosensitive layer - its ability to transform the details of the subject into a sharp photographic image - diminishes at either end of the exposure scale, but this often occurs with exaggeration in the exposure that exceeds what is necessary. So, with declining dissolution. The picture, the appearance of the granulation structure will be more clear.
We note from all this that the overall effect in the finished photographic image depends on a large number of factors. These factors affect the apparent measure of penetration, if they do not affect the actual measure of each individual point within the negativity.
It should be added here that the graining structure of the print paper is too soft to play an actual role in the appearance of the finished photograph, as long as graining is what is intended.

Minimum amount of percolation:
In order to obtain the least amount of grain in the final edition, the following few simple guidelines can be used:
⏺ Working with the slowest film possible, with the finest flour.
⏺ Working with the best available lens - the higher the dissolution energy (*) of the lens, the clearer the image will be, and the less clear the graininess will be.
⏺ Let the exposure be perfectly correct, because the dissolution energy in the film is at its highest at that time.
⏺ You should avoid having large areas that fall out of focus in the image, as long as these areas attract attention to the grain.
⏺ Work with the largest possible negative structure, as long as it needs the least amount of enlargement to make a print of a certain scale.
In these ways, we confirm that the image was projected onto the film as close as possible to the theoretical ideal situation. We can also exercise more of this control and control, by developing and printing the film.