Camera lens, essentially Crossword Clue

 The answer to the crossword clue "Camera lens, essentially" is aperture. 

The aperture is an opening in the lens of a camera that allows light to pass through. The size of the aperture is measured in f-stops. A larger f-stop number means a smaller aperture opening, which lets in less light. A smaller f-stop number means a larger aperture opening, which lets in more light.

The aperture is one of the three main controls of a camera, along with shutter speed and ISO. The aperture controls the amount of light that reaches the camera sensor, which affects the brightness of the image. It also affects the depth of field, which is the amount of the scene that is in focus.

A wider aperture (larger f-stop number) will let in more light and create a shallow depth of field, which means that only a small part of the scene will be in focus. A narrower aperture (smaller f-stop number) will let in less light and create a deeper depth of field, which means that more of the scene will be in focus.

The aperture is an important tool for photographers to control the look of their images. By adjusting the aperture, photographers can create different effects, such as blurring the background or bringing the foreground into focus.