Mechanical Shutters
In photography, the sensor (or film in the past) is responsible for capturing light, but an external mechanism is required to initiate and terminate this process, which is where the shutter comes in. Mechanical shutter systems exist in various forms, with the most common being the two-curtain system that starts and ends the exposure.
There are technically two sets of curtains with multiple blades in each set, known as the first and second curtain shutters, respectively. These are present in about 99% of current mechanical shutter systems.
The curtains in mechanical shutter systems move swiftly and halt abruptly, leading to a major issue of camera shake. Due to the lightweight of their components, the force generated by them is limited, and this problem often goes unnoticed.
However, when using a telephoto lens in combination with modern sensors having high megapixel counts, even the slightest camera shake becomes noticeable. Delaying the shutter release doesn’t alleviate the problem because the impact of the curtain shutters takes place at the start of the exposure (and again at the end, which is of no consequence).
When it comes to using Flash and very fast shutter speeds, there is another issue with mechanical shutters. Although the curtains may be fast, they have their limitations. At extremely high shutter speeds, such as 1/4000s, the first curtain opens and exposes the sensor, but the second curtain doesn’t wait for the first one to close. Instead, it opens after a brief pause while the sensor is still covered.
Combining this process with Flash can lead to an issue where there isn’t enough time for the Flash to fully activate. As a result, only the recently exposed area of the sensor receives the Flash’s illumination, leaving the remaining area in darkness.
Special flash programs exist to address this problem, but they are not always available and may not be very effective. While this issue affects other types of shutters as well, we won’t delve into it further in this article. Future innovations may offer solutions to this problem.
The movement of shutters imposes a constraint on the number of frames per second that a camera can capture. In other words, mechanical systems have limitations in their speed of operation.
Additionally, mechanical shutters have a finite lifespan and may require servicing when they fail. The duration of their lifespan is subject to change, with some shutters failing after just 100,000 shots while others remain functional for millions of exposures.
