Glossary |
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| Depth of field | The area in front of and behind a focused subject in which the photographed image appears sharp. In other words, the depth of sharpness to the front of sharpness to the front and rear of the subject where image blur in the film plane falls within the limits of the permissible circle of confusion. Depth of field varies according to the lens\' focal length, aperture value and shooting distance, so if these values are known, a rough estimate of the depth of field can be calculated using the following formulas:
Front depth of field = d x F x a2 / (f2 + d x F x a)
Rear depth of field = d x F x a2 / (f2 - d x F x a)
f: focal length
F: F number
d: minimum circle of confusion diameter
a: subject distance (distance from 1st principal point to subject)
If the hyperfocal distance is known, the following formulas can also be used:
Near Point limiting = Hyperfocal distance X shooting distance
Hyperfocal distance + shooting distance
Far Point limiting = Hyperfocal distance X shooting distance
Hyperfocal distance – shooting distance
(Shooting distance: Distance from film plane to subject)
In general photography, depth of field is characterized by the following attributes:
1. Depth of field is deep at short focal lengths, shallow at long focal lengths.
2. Depth of field is deep at small apertures, shallow at large apertures.
3. Depth of field is deep at far shooting distances, shallow at close shooting distances.
4. Front depth of field is shallower than rear depth of field. |
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| Depth of focus | The area in front of and behind the focal plane in which the image can be photographed as a sharp image. Depth of focus is the same on both sides of the image plane (film plane) and can be determined by multiplying the minimum circle of confusion by the F number, regardless of the lens focal length. With modern autofocus SLR cameras, focusing is performed by detecting the state of focus in the image plane (film plane) using a sensor which is both optically equivalent (1:1 magnification) and positioned out of the film plane, and automatically controlling the lens to bring the subject image within the depth of focus area |
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| Diffraction | A phenomenon in which light waves enter the shadow area of an object. With a photographic lens, exposure is often adjusted by varying the size of the lens\' diaphragm (aperture) to adjust the amount of light passing through the lens. Diffraction in a photographic lens occurs at small apertures where the diaphragm edges obstruct the straight-line path of advancing light waves, causing light rays passing near the edge of the diaphragm to bend around the edges as they pass through the diaphragm. |
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| Diffractive Optics | Diffractive Optics, a revolutionary new lens optical technology that permits super-telephoto lenses that are significantly shorter and lighter than previously possible, while simultaneously improving optical performance by reducing chromatic aberrations and even spherical aberrations. |
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| Diopter | The degree to which the light ray bundles leaving the viewfinder converge or disperse. The standard diopter of all EOS cameras is set at - 1 dpt. This setting is designed to allow the finder image to appear to be seen from a distance of 1m. Thus, if a person cannot see the viewfinder image clearly, the person should attach to the camera\'s eyepiece a dioptric adjustment lens having a power which, when added to the viewfinder\'s standard diopter, makes it possible to easily see an object at one meter. The numerical values printed on EOS dioptric adjustment lenses indicate the total diopter obtained when the dioptric adjustment lens is attached to the camera. |
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| Dispersion | A phenomenon whereby the optical properties of a medium vary according to the wavelength of light passing through the medium. When light enters a lens or prism, the dispersion characteristics of the lens or prism cause the index of refraction to vary depending on the wavelength thus dispersing the light. This is also sometimes referred to as color dispersion. |
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| Distance information | D-type and G-type NIKKOR lenses relay subject-to-camera distance information to AF Nikon camera bodies. This then makes possible advances like 3D Matrix Metering and 3D Multi-Sensor Balanced Fill-Flash.
Note: D-type and G-type NIKKOR lenses provide distance information to the following cameras: Auto exposure; F6, F5, F100, F90X, F80, F75, F70, F65, F60, F55, F50, PRONEA S, PRONEA 600i, D2 series, D1 series, D100 and D70s/D70.
Flash control; F6, F5, F100, F90X, F80, F75, F70, D2 series, D1 series, D100 and D70s/D70. |
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| Distance of incidence | Distance from the optical axis of a parallel ray entering a lens. |
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| DX | Compact and lightweight DX NIKKOR lenses featuring a smaller image circle are specially designed and optimized for Nikon D2-series, D1-series, D100 and D70s/D70 digital SLR cameras. These are ideal options for landscape photographers and others who need to shoot expansive scenes with Nikon DX-Format digital SLRs.
Note: We do not recommend use of DX NIKKOR with 35mm (135) or IX240 format cameras. |
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