We often hear about the optical construction of objectives, the lenses that compose them and the groups in which the internal elements are organized, aspects that determine their optical quality, but we do not have much opportunity to know how they are. really inside. In this article, find out everything you need to know about your goal structure.
Unlike other manufacturers, DZO presents on its website the construction of its lenses and for the first time, the manufacturer reveals that of three of them: the 8mm, 24mm and 85mm. This makes it easier to appreciate the arrangement of elements and groups inside, key factors in achieving the brightness and image quality characteristic of the South Korean brand.
We will quickly review what elements like internal goal groups are, what role they play, as well as the aberrations they prevent to achieve optimal results. We will also explain the characteristics of the UMC coating present on most of these lenses and those of the NCS, the new high-tech coating integrated into the brand’s latest launches, to better understand the functions and advantages they offer.
Early photo lenses only had a single lens capable of converging approximately all of the light beams to a single point, so that they imprinted the image on a photosensitive material. It is the principle of the focal length which is defined as being the space between the objective and the zone where the light rays cross. This simple system, composed of a single optical element called a meniscus, causes countless problems of aberrations and sharpness since it cannot allow the rays to converge on exactly the same point.
The solution: the elements and groups of a goal
Lenses exhibit seven types of aberrations: aspherical, chromatic, lateral chromatic, coma, astigmatism, field curvature and curved distortion. To correct them and achieve better optical performance that gives the lens greater image quality and enhances contrast, the engineers who design each focal length incorporate more lenses so that they can correct these side effects.
Currently, an objective is composed of a series of polished lenses with different radii of curvature and produced with special glasses of great homogeneity, and with specific chemical treatments.
The lenses of an objective are in turn gathered into specific groups to combat each of the aberrations more effectively. These groups combine convergent lenses (wider in the center than at the edges) and aspherical (non-circular) and divergent (wider at the ends) lenses.
These sets of lenses have the property of gradually redirecting the light beam in a more precise manner, so that a well-constructed, many-element optic will eventually pass light in the same way as a single lens, but with l ‘advantage of having corrected all the aberrations and reinforced the sharpness of the whole.
The quality of the lenses used and the number of integrated lenses are the two factors that determine the quality of a lens, as well as its price. This is the reason why it is customary to say that objectives with a greater number of elements and groups, the difference in weight of which can be appreciated just by holding them in the hand, are those which display the higher optical quality. This is the case with DZO lenses which incorporate a large number of high quality lenses and which benefit from specific chemical treatments.
Another aspect to take into account in the construction of the lenses is the coating they include in some of their elements to improve the optical quality.
DZO incorporates in most of its lenses the UMC coating on all its elements, a multilayer anti-reflective coating, which guarantees optimal light transmission. For cinema lenses, the data is arranged parallel to the optical axis of the lens to make it easier to read the focus and the aperture scale.
For its latest launches (12 mm and 10 mm), the brand has introduced a new coating: NCS or coating of nanocrystals , which has a lower reflection factor than UMC and which provides better light transmission and more marked contrast.