العدسات ذات البؤرة الناعمة .. كتاب آلة التصوير

Soft focus lenses

The lens maker aims for the lens to be able to produce images. Exactly in order to suit works that require accuracy and finite unity, such as imaging for scientific research purposes or photographic transmission operations Reproduction..etc. However, the photographer may sometimes see that this extreme sharpness is undesirable, as if he wanted to photograph the face of a child or a lady, and these are cases in which the photographer - or the owner of the picture at least - hopes that the photographer will remove all wrinkles, holes in the pores in the skin, or signs of aging in her face. ..etc. Therefore, special methods are followed that blend the borders of the shadows areas with the areas of light (or high lighting) in order for the image to acquire a soft, dreamy character and reduce the degree of contrast (compare between Figures 62 and 61). These lenses are called “soft lenses” and sometimes soft lenses. Soft focus lenses. Just as these lenses are suitable for portrait photography, they are also suitable for photographing landscapes, as they give them a calm character that can be likened to what we see before the morning “rusk” disappears.

Softning the focus may be done during imaging or during positive image enlargement. It is generally summarized in the formation of two images, one of which is completely sharp, and the other is mixed with it and is not sharp. By mixing the two images, this soft effect is created without the final image being considered blunt.

There are many methods that lead to smoothing the image, we will confine ourselves to explaining some of them as follows:

(a) That the lens is originally prepared for this purpose, by deliberately not correcting the defect of spherical aberration, and thus every point of light emanating from the object is represented on the image as a point also surrounded by a light halo, so the sum of these light halos spreads over the entire area of ​​the image forming a curtain In this case, the use of soft-focus lenses differs from the case of
Shooting without adjusting the distance accurately.

In order for this desired soft effect to be clear, and to facilitate the achievement of this gross aberration, it is always better for the aperture of the diaphragm to be wide at its maximum.

(b) A so-called Diffusion disc should be placed in front of the lens, which is a piece of glass with narrow or wide circular protrusions (Fig. 60) placed in front of the lens in the same way as any optical filter. This protrusion may be rather than circular, but the latter is always preferred.

(C) It is easy for the photographer to come up with a way to achieve this purpose, for example by using a piece of plastic or glass with circular holes on it. It is also possible to do so by putting any thin transparent fabric (such as a piece of nylon stockings that women use).