Photography Goals Angle Of View Object

Photography Goals Angle Of View Object

The second is related to a possible circular polarization filter that we have mounted in front of our goal we will have to go to readjust every time we act on focus. Not really comfortable.

We pass to the problem of chromatic aberrations. As already described in the chapter of the aberrations, the different wavelengths corresponding to the different colors have different speeds.

The short-wave (blue) are slower of long waves (colors toward red), and then arrive in delay on the sensor The more slow-wave will suffer a greater refraction in the transition from the lens (and all the other passages of material) than the longer waves. It follows that the optics will not be able to focus all the colors perfectly if we assume to focus the green, the optical focus the red after the sensor and the blue first of the sensor. This problem is precisely the chromatic aberration.

What to check when buying a lens We must determine whether it is a traditional objective, achromatic or apochromatic. In the case of an achromatic objective, it means that this is able, thanks to the combination of different optical elements (to glass and other low dispersion, for example), to focus two primary colors. In the case of apochromatic lenses (whose cost is very high), the same is capable of focusing all three primary colors.

Also eye the longitudinal chromatic aberration. It ‘similar chromatic aberration described before but, because of the always different speed, the light rays which affect the lens in an oblique manner will be to focus at different points of the sensor (higher and lower, as shown in the figure above ). As in the case of the first, assuming properly focus the green, we will have the blue (slower moving) focused upwards while the red more downward. This aberration is corrected only in expensive apochromatic objectives, the same that correct chromatic aberration seen before. Infrared Warning Apochromat are built to correct the visible light, so sull’infrarosso behave as if they were traditional targets. Also remember that the longitudinal aberration is also corrected simply by reducing the lens aperture.

The spherical aberration is the third aberration to be taken into account during the purchase of a goal. This type of aberration is the inability of a single lens to focus more parallel rays in the same punto.I rays which strike the edges of the lens, because of the greater path to take to reach the sensor, first focus of the same sensor, as well as the rays that pass through the center of the focus lens after the sensor.

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