Autodynamic exposure control
Auto Dynamic exposure control (also autodynamic metering or autodynamic measurement control called) is a mid-1970s by Olympus developed metering system for SLR that when shooting with flash light has and long exposures advantages over the formerly standard metering modes. A special feature of this method is the detection of the light diffusely reflected from the film ("off the film", OTF) during the recording.
The Olympus OM-2 was the first camera to be equipped with autodynamic exposure control.
functionality
Autodynamic exposure control is a through-the-lens (TTL) method, which means that the light is captured by the photo lens.
Before triggering: As long as the partially transparent main mirror is not folded up, the light falls through it onto a mirror placed behind it. This is designed similar to a Fresnel lens and bundles the light so that the light beam falls on the measuring cell on the bottom of the camera.
When the shutter is released : While the shutter is released, the camera saves the measured value and releases the first shutter curtain. This process takes approx. 60 ms. Depending on whether the shutter speed is below or above 1/60 second, the procedure is different:
1. When the shutter speed is less than 1/60 second
- The camera performs the exact shutter speed of the stored reading. This corresponds to a conventional TTL exposure measurement.
2. When the shutter speed is over 1/60 second without the flash
- The camera measures the light reflected from the film during the exposure process and then closes the shutter when there is enough light - for a correct exposure - on the film. The method is also suitable for night shots and reacts correctly to changes in brightness during the recording.
When shooting with the flash: The light reflected from the film is detected. As soon as enough light has reached the film, the flash tube is switched off very quickly, as with conventional computer flashes. The autodynamic exposure control is therefore a TTL flash measurement that does not require a pre-flash to determine the optimal amount of light.
Individual evidence
- ↑ 1975: Olympus OM-2. kleinbildkamera.ch, accessed on April 27, 2017 .
- ↑ Olympus OM Flash Photography - Part 1. Archived from the original on January 3, 2014 ; accessed on April 27, 2017 (English).