What impacts the resolution and light-gathering ability in optical systems?

The aperture of the optical system plays a crucial role in determining both the resolution and light-gathering ability. The aperture refers to the opening that allows light to enter the optical system, and its diameter directly influences how much light is collected from the scene being observed. A larger aperture can gather more light, which is particularly beneficial in low-light conditions, allowing for better image quality and enhanced resolution by capturing finer details.

In addition to improving light-gathering capacity, a larger aperture also affects depth of field, which is the range of distance within a photo that appears acceptably sharp. It enables the optical system to achieve better separation of subjects from the background, further enhancing visual clarity and resolution.

The other options may relate to the optical performance, but they do not directly impact both resolution and light-gathering ability in the same way that the aperture does. The type of lens used can affect image quality and distortion, as well as how the lens interacts with light; however, the lens type doesn't inherently define the amount of light gathered. Similarly, the total light output is more about the system’s overall light performance rather than a specific characteristic like aperture size. The size of the sensor influences the image detail and quality once the light is captured,