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Additional parts for close-up photography .. Choosing and using materials .. Book of photography

Choosing and using materials
Additional parts for close-up photography

Close-up photography is the method we use when we photograph a subject that is at a distance that cannot be measured by the lens or by the normal mechanism of the machine. This concept is also defined according to the degree of magnification of the image. Let us say that the term (close-up image) is used especially for magnifications between × 0.10 and × 1, that is, when the image of the subject has a size between 1/10 and 1/1 of the size of the subject itself. The term (photomacrography) refers to magnifications between × 1 and × 10, while (photomicrography) refers to higher magnifications and applies to the image taken by a microscope.

There are several ways to obtain these magnifications or magnifications: using a special long-pulse lens or by placing zoom rings or a small bellows between the lens and the machine case or by using lenses that are mounted in front of the normal lens. The choice of method depends on the range of magnifications we want to reach and the machine we have. However, not all of these methods can be applied to all machines. Let us mention here that magnifying the image in the laboratory is also a means of (bringing closer) to the subject.

When the calibration has been done on something close to the lens, the depth of field is quite limited. However, if we open the pupil to its maximum, of course we can increase this depth, but at the expense of a long stop, which makes taking close-up pictures by hand difficult. For this reason, it is always preferable to work on a support with a flexible button. Moving the subject is another problem that can sometimes be solved by using a small air-tight wall (a picture of a flower, for example).

The distance between the lens and the film (i.e. the clouds) increases with magnification, which always requires an increase in exposure. The illumination of the film decreases like a cloud square. In a machine that does not include a light measuring device (bosomemeter), the (normal) exposure must be corrected (for a distance of several meters) by applying the exposure factor indicated by a table such as the one on page 215. As for the built-in bosonometer, there is no problem since the cell behind the lens measures the light that actually reaches the film. In this respect, the modern 24 x 36 reflex is better equipped than other close-up cameras.

In non-reflex machines (except for very large professional machines where the calibration is done on the opaque glass)

(The zoom bellows: It is placed between the lens and the case and is on the same principle as the extension rings but allows for more significant magnifications and more precise values)

(Photography with the aid of a microscope: Thanks to a special mount we can mount the machine on the microscope. And the magnifications exceed 10 x)

Parallax angle errors are a real problem. Some of these machines are equipped with a correction for the parallax angle either by the movable collimator frame or by a mark on the optical collimator.

- (Macro) lenses.
Most of the regular focal length lenses for the single-lens reflex machine have a minimum calibration of about 45 cm. However, there are special lenses called macro lenses whose fan frame is a large expansion which increases and allows calibration at very short distances. The magnification of the image lengths compared to the subject lengths is usually indicated on the lens frame and its maximum value is often 0.5 and sometimes × with a macro lens the pupil must be opened to obtain sufficient clarity.

- Zoom rings:
These rings of different lengths are placed between the case and the lens in single-lens reflex machines, of course if the lens is removable and reversible. They are usually sold in a series of two or three rings, each of which can be used separately or connected with different lenses, allowing for various magnifications (see table in 215). The longer the ring, the larger the image. The disadvantage of the ring is the time it takes to remove it and put another ring on to obtain a different magnification. The depth of field is limited because it is only related to magnification, here too it is necessary to work with a small aperture.

Lighting subjects photographed at a short distance sometimes poses some problems because the machine, the zoom ring and its lens are very close, stopping part of the subject in some way. This is why some specialists prefer to use a lens with a focal length greater than the normal 85 or even 135 mm 24 x 36. This way we can work from a greater distance and thanks to longer rings we get a sufficiently enlarged image of the subject.

- The portable collecting lens:

It is simply a collecting glass lens that is fixed to the objective lens in the manner of a filter: which allows calibration on close objects. It is used only in principle in machines with fixed objective lenses where neither connecting rings nor bellows can be used. The power of the collecting lens is expressed in diopters: the magnification increases as the power of the lens increases. We can never exceed a power of three diopters without modifying the image value.

We can use two superimposed collecting lenses to increase the total power. Thus, a collecting lens with a power of one diopter superimposed on a lens with a power of two diopters gives a total power of three diopters. The power of a lens in standard diopters is the inverse of its focal distance expressed in meters. Thus, a lens with a power of two units has a focal distance = 1/2 = 0.50 meters.

- Connection bellows:

The bellows are used like rings but with one difference, which is that their extension allows for adjusting the required amplification accurately and continuously, on the other hand we can get large amplifications. The size of the bellows is its only drawback.

- Photomicrography:
For very important amplifications, the photographic device can be mounted on a microscope and fixed on it. The lighting must be bright and constant so that the image capture time is not long. The pseudometer inside the reflex device helps determine the exposure time, otherwise prior experiments must be made to find the correct stop.

- Lens reversal

Unlike the normal machine lens, we work at a shorter distance and the image quality is better.

There are rings to reverse the lens.

- Macro lens
The lower macro lens differs from the upper normal lens in its frame that has a larger extension, which gives greater amplification of the subject.

- Zoom rings:
They are sold in a set of three and are used individually or together. They are placed between the lens and the machine body.

Converging lens: It is mounted on the lens in the manner of a filter and it shortens the focal point of the lens, resulting in greater magnification.

It is only used with fixed lens instruments.

- Zoom rings used with 35 mm resolution at 45 cm Ring 9.5 = 1 mm -
Ring 19 = 2 mm Ring 23.5 = 3 mm

- Zoom rings used with 55 mm resolution at 45 cm

' Zoom rings used with 135 mm resolution at 1.50 m

- Zoom bellows used with several lens burners Minimum elongation = 38 mm Maximum elongation = 178 mm

Amplification scale: With the help of the various additional parts mentioned above, we can reach various amplification series: The graph below indicates the limits of each type of instrument.