Comparison Tamron 28-75mm f/2.8 RXD Di III vs Sony 18-105mm f/4.0 G E OSS

The result shown by the lens in the DxOMark rating.

DxOMark is one of the most popular and authoritative resources for expert testing of photography devices. According to the test results, the lens receives a certain number of points; The more points, the higher the final score.

Lens aperture is a characteristic that determines how much the lens attenuates the light flux passing through it. It depends on two main characteristics — the diameter of the active aperture of the lens and the focal length — and in the classical form is written as the ratio of the first to the second, while the diameter of the active aperture is taken as a unit: for example, 1 / 2.8. Often, when recording the characteristics of a lens, the unit is generally omitted, such a record looks, for example, like this: f / 1.8 or f/2.0. At the same time, the larger the number in the denominator, the smaller the aperture value: f / 4.0 lenses will produce a darker image than models with f / 1.4 aperture.

Zoom lenses usually have different aperture values for different focal lengths. In this case, the characteristics indicate two aperture values, for the minimum and maximum focal lengths, respectively, for example: f / 4.5-5.6

The larger the aperture of the lens, the shorter shutter speeds it allows you to use when shooting. This is especially important when shooting fast-moving subjects, shooting in low light, etc. And if necessary, the light stream transmitted by the lens can be weakened using a diaphragm (see below).

Another point that directly depends on this indicator is the depth o...f field (the depth of space that is in focus when shooting). The higher the aperture, the smaller the depth of field, and vice versa. Therefore, shooting with artistic background blur (bokeh) requires high-aperture optics, and for a large depth of field, you have to cover the aperture.

This parameter determines the size of the area of the scene being shot that falls into the frame. The wider the viewing angles, the larger the area the lens can capture in one shot. They are directly related to the focal length of the lens (see "Focal length"), and also depend on the size of the specific matrix with which the optics are used: for the same lens, the smaller the matrix, the smaller the viewing angles, and vice versa. On our website, in the characteristics of optics, viewing angles are usually indicated when used with the matrix for which the lens was originally designed (for more details, see "Matrix Size").

Aperture is a design of several blades-curtains, which allows, if necessary, to reduce the diameter of the active aperture of the lens, actually reducing its aperture (for more details, see "Aperture"). In addition to reducing the light output (which can be relevant, for example, in bright sunlight), closing the aperture has another effect — it increases the depth of field. In other words, “in focus” is a larger volume of space than with an open aperture.

The values on the aperture scale are usually selected from a standard range. The numbers in it actually indicate what aperture the lens will have when the aperture is closed to a given value: for example, an aperture value of 5.6 will correspond to f / 5.6 aperture. The larger the number indicating the minimum aperture value, the more options the photographer has and, accordingly, the possibilities for setting the shooting mode (ceteris paribus).

Minimum focus distance (m) - the smallest distance from which you can focus on an object and take a photo. Usually it ranges from 20 cm for wide-angle lenses to several metres for telephoto. In the macro mode of the camera or with the help of macro lenses, this distance can be less than 1 centimeter.

The degree of magnification of the object being shot when using a lens for macro shooting (that is, shooting small objects at the maximum possible approximation, when the distance to the subject is measured in millimetres). The degree of magnification in this case means the ratio of the size of the image of the object obtained on the matrix of the camera to the actual size of the object being shot. For example, with an object size of 15 mm and a magnification factor of 0.3, the image of this object on the matrix will have a size of 15x0.3=4.5 mm. With the same matrix size, the larger the magnification factor, the larger the image size of the object on the matrix, the more pixels fall on this object, respectively, the clearer the resulting image, the more details it can convey and the better the lens is suitable for macro photography. It is believed that in order to obtain macro shots of relatively acceptable quality, the magnification factor should be at least 0.25 – 0.3.

The size of the matrix for which the lens was originally designed.

The formats (and sizes) of modern matrices can be indicated diagonally in inches (1/1.8", 1/2.3" — in this case, the conditional "Visicon" inch is taken, which is about 17 mm), according to the actual dimensions (13.2x8.8 mm) or by symbol (APS-C, full frame). In general, the larger the sensor, the more advanced and expensive it is.

Among modern lenses, solutions for such matrix formats are most popular, in ascending order of size: 4/3(17.3x13 mm, used in cameras of the Four Thirds and Micro Four Thirds standards), APS-C(23x15 mm with slight variations, SLR and MILC cameras of the middle class), full frame(36x24 mm, the size of a standard film frame — advanced DSLRs), big frame(anything larger than full frame — high-end professional cameras). Optics for other formats is somewhat less common.

Note that it is technically allowed to use with “non-native” sensors, however, in such cases, the performance characteristics of the optics will differ from those claimed. So, when installed on a smaller matrix (for example, a full frame lens on an APS-C camera), only a part of the image created by the lens will fall on such a sensor. As a result, the space that gets into the frame will be narrower, and the details in the frame will be larger, as if the focal...length of the lens has increased (although it has remained unchanged, only the matrix has changed). And when installed on a larger sensor, the covered space will increase, the detail will decrease; in some cases, the size of the “picture” provided by the lens may simply not be enough for the entire area of the matrix, and the pictures will be obtained with black space around the edges.

A type of drive that ensures the movement of lens structural elements during automatic focus. Currently, the following types can be used:

— Ultrasonic motor. The most advanced type of drive to date. Ultrasonic motors are much faster than conventional motors, provide higher accuracy, consume less power and are virtually silent. However, their cost is quite high.

— Stepper motor. Drive control focal length and zoom (zoom). This type of motor is used for the most part only in full-size digital cameras. Among the advantages of a stepper motor, one can note: high reliability and accuracy of operation; in addition, it does not require power supply to maintain focus and zoom. Of course, stepper motors are not without drawbacks. Among the minuses can be identified: slow speed and increased noise. Additionally, a stepper motor is characterized by large dimensions and a rather large weight, which physically does not allow this type of drive to be integrated into the optics of mobile phones and ultra-compact cameras.

— Motor. In this case, an electric motor of a traditional design is meant. Such drives are simple and, as a result, inexpensive. Their disadvantages are the relatively low speed of operation, as well as the noise produced during this; the latter can sometimes be critical — for example, when shooting wildlife. Recently, designers have been us...ing various tricks to neutralize these shortcomings, but in general, the characteristics of conventional motors still remain relatively modest.

— Is absent. The complete absence of an autofocus motor in the lens. Focus such optics can be carried out either by the “screwdriver” system, or strictly manually (for more details on both options, see below).

The presence in the lens of its own image stabilization system. Such a system includes gyroscopes and movable lenses that compensate for small tremors of the lens and prevent the appearance of “shake”. Stabilization is especially relevant when shooting handheld, especially at slow shutter speeds and/or at long distances with high magnification: it is in such conditions that “shake” affects the quality of the image the most. At the same time, it should be taken into account that the presence of a stabilizer significantly affects the weight, dimensions and, above all, the price of optics; at the same time, some modern cameras have their own stabilization systems (due to matrix shift). Therefore, it makes sense to choose a lens with this function in the case when maximum protection against “shake” is of fundamental importance.