What factor primarily influences the resolution in a photograph?

The primary factor influencing the resolution in a photograph is the sensor size. A larger sensor can capture more light and detail, providing higher resolution images. It can gather more information from the scene due to its increased surface area, resulting in better image quality and detail. When a digital camera's sensor is larger, it can also facilitate the production of larger photos with more pixels, which directly correlates to higher resolution.

While other factors, such as shutter speed and aperture size, play significant roles in exposure and depth of field, they do not directly affect the resolution of an image. The quality of the lens is also important, as it can influence sharpness and clarity, but even the best lens will not produce high resolution images if used with a smaller sensor. Thus, sensor size is the key determinant for resolution in photography.