Flash Guide Number Film

Until Mount used the thread (two types), which has been preserved in some cells to date. Bayonet compared with thread has many advantages, the main ones – the possibility of more rapid replacement of optics and more exact adjustment of the lens (unlike the bayonet thread has a fixed position), as well as ease of transferring information from the body to the lens. Hood – a fixture in the form of a hollow truncated cone or truncated pyramid of plastic that is worn on the camera lens. Hood prevented from entering the lens of the light rays that are not involved in the formation of an image, preventing glare in the picture. Size is determined by the blend characteristics of the lens.

Mistakes in choosing a blend can lead to vignetting images (shading peripheral areas of the picture). Bracketing – an automatic burst mode, in which each frame withdrawn at different offsets relative to each other exposure settings (with different and diaphragm), with underexposure and overexposure. This mode is usually used in complex lighting conditions, when heavy accurately determine the required aperture and shutter speed. Flash Guide Number: The maximum distance (in meters or feet) at which the flash can illuminate the subject for correct exposure at aperture f / 1 and the film is ISO100. For example: flash with guide number of 56, when shooting on film ISO100 and f/5.6 aperture properly illuminate the object at a distance of 10m, while shooting the film ISO400 – 20m. The general formula relating the number of leads to the diaphragm and the distance: Distance = vc / F / number for the film ISO100.

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