For a given subject framing and camera position, the DOF is controlled by the lens aperture diameter, which is usually specified as the f-number, the ratio of lens focal length to aperture diameter.
22.
These were early attempts by Nippon Kogaku to provide shutter priority autoexposure by having an electric servomotor automatically turn the lens aperture ring in response to the set shutter speed and light meter reading.
23.
The FT can also operate the later Canon FD series lenses in stop-down mode, but the earlier R series has a different lens aperture mechanism and cannot be used, although the bayonet fitting is similar.
24.
Contemporary photographic convention denotes lens apertures with a slash, such as 22 or 64, but in its writings the group always used a dot or period instead ( as in " f . 64 " ).
25.
The photographer would adjust the shutter speed to freeze or blur motion and / or the lens aperture f-stop to control depth of field ( focus ) until the needle was centered between two pincer-like brackets.
26.
It is called " subjective " because the detailed structure of the speckle pattern depends on the viewing system parameters; for instance, if the size of the lens aperture changes, the size of the speckles change.
27.
The dial above the shutter button will adjust the shutter speed in shutter priority Tv / Time value mode, but in aperture priority Av / Aperture value mode this same dial will adjust the lens aperture.
28.
Preset aperture controls have taken several forms; the most common has been the use of essentially two lens aperture rings, with one ring setting the aperture and the other serving as a limit stop when switching to working aperture.
29.
The " Follin ophthalmoscope " was an early model of ophthalmoscope & mdash; it contained four correcting lenses mounted in a revolving disk so that each lens may be rotated in front of the lens aperture of the device.
30.
Exposure metering is through-the-lens ( SLR lenses, where the diaphragm controlling lens aperture is generally closed only at the time of shutter release, rangefinder camera lenses close or open the diaphragm directly as the aperture control is applied ).
