Pentax Camera-Body Terminology

Pentax Camera-Body Terminology

  • Aperture priority (Av): exposure program where the photographer sets the aperture-value and the camera adjusts the shutter-speed so that a well-exposed image is be produced.
  • Bulb (B): shutter operational mode where the shutter opens when the shutter release-button is pressed and closes when shutter release-button is released. Usefull for exposures of one second or longer. Cameras with an electrical shutter consume lots of energy to keep the shutter open.
  • CdS: light-meter material (Cadmium Sulfide) also known as LDR (Light-Dependent Resistor). Requires very simple circuits for operation, but is not very sensitive to low light and needs up to a second or more to achieve a stable reading in low light. Typically used in cameras in the 1960’s and mid 1970’s.
  • DOF-preview: an operational mode where at the press of a button the aperture is closed to the actual position as if a picture is being taken. In this way the photographer can visially evaluate the depth-of-field before taking the image.
  • Flash-sync speed (X): the shortest shutter speed at which a flash photograph can be taken. Shutters consist of two moving curtains — the first curtain opens, the film or sensor gets exposed, then the second curtain closes. If the shutter speed is long enough, there is a long period of time between the opening of the first curtain and closing of the second curtain; if the shuter speed is very short, the first curtain is still opening while the second curtain starts closing. The X-speed is the shortest speed at which the first curtain completely opens before the second curtain starts closing.
  • GPD: light-meter material (Gallium-arsenide Photo Diode). More sensitive to visible and less senstive to infra-red light than silicium, but rarer and more expensive. Used in some Pentax cameras from the mid-1980’s.
  • Hyper manual (HyM): A combination of P and M. Pressing a specially designated button selects a combination of aperture-value and shutter-speed, as if in Program-mode. Turning one wheel activates M and changes the shutter-speed without changing the aperture-value. Turning another wheel also activates M and changes the aperture-value without changing the shutter-speed. Pressing that special button at any time returns you to an aperture-value and shutter-speed according to the P-mode and the current lighting conditions. The light-meter in the body is active at all times and shows you how the currently-selected exposure-value differs from the one that the body would select in some program mode.
  • Hyper program (HyP): A combination of P, Tv and Av. Pressing the shutter-button half-way sets the aperture-value and the shutter-speed, as if in Program-mode. Turning one wheel activates Tv — the photographer chooses the shutter-speed, the camera responds by adjusting the aperture-value. Turning another wheel activates Av — the photographer chooses the aperture-value, the camera responds by adjusting the shutter-speed. Pressing a specially designated button returns you to P, and the camera sets both the aperture-value and the shutter-speed. This sounds complicated, but is very easy to use.
  • Manual exposure (M): Exposure mode in which the photographer sets both the aperture-value and the shutter-speed.
  • Mirror lock-up: Feature of some cameras which allows the mirror to be locked in its up position before taking an image. This reduces the vibrations during exposure and contributes to the sharpness of the images, especially at shutter speeds around 1/30 sec.
  • Program (P): Exposure mode in which the camera determines both the aperture-value and the shutter-speed.
  • Sensitivity priority (Sv): exposure program just like Program, but the rear dial adjusts the ISO value.
  • Shutter priority (Tv): exposure program where the photographer set the shutter-speed and the camera adjusts the aperture-value so that a well-exposed image will be produced
  • Shutter-Aperture priority (TAv): exposure program where the photographer sets the shutter-speed and aperture-value the camera adjusts the ISO value.
  • SPD: light-meter material (Silicium Photo Diode). Ideal for light-meters, very fast and sensitive, good enough for flash metering, cheap to produce. On the other hand it is sensitive to infra-red, so light-meters typically incorporate a blue filter and a signal amplifier. Used in bodies from 1975 till today.