Camera vs Eyes: Similarities
To better understand the answer to this question, let’s first have a quick comparison of various similarities and differences found in the working of the human eye and a photo camera.
Image focusing: Human and camera lenses both focus an inverted image onto light-sensitive surface. In the case of a camera, it’s focused onto film or a sensor chip. In your eyes, the light-sensitive surface is the retina on the inside of your eyeball.
Light adjustment: Both the eye and a camera can adjust quantity of light entering. On a camera, it’s done with the aperture control built into your lens, whilst in your eye, it’s done by having a larger or smaller iris.
Camera vs Eyes: Differences
Absolute versus subjective measuring of light: Simply speaking, the human eye is a subjective device. This means that your eyes work in harmony with your brain to create the images you perceive: Your eyes are adjusting the focus (by bending the light through the lens in your eyeballs) and translating photons (light) into an electrical impulse your brain can process. From there onwards, it’s all about your brain: It is continuously readjusting its colour balance according to the lighting context. In other words, our eyes know what must be seen as red or white or black etc.
A camera, on the other hand, is an absolute measurement device — It is measuring the light that hits a series of sensor, but the sensor is ‘dumb’, and the signals recorded need to be adjusted to suit the color temperature of the light illuminating the scene, for example
Lens focus: In camera, the lens moves closer/further from the film to focus. In your eyes, the lens changes shape to focus: The muscles in your eyes change the actual shape of the lens inside your eyes.
Sensitivity to light: A film in a camera is uniformly sensitive to light. The human retina is not. Therefore, with respect to quality of image and capturing power, our eyes have a greater sensitivity in dark locations than a typical camera.
There are lighting situations that a current digital cameras cannot capture easily: The photos will come out blurry, or in a barrage of digital noise. As an example, when observing a fluorescence image of cells under a microscope, the image you can see with your eyes would be nigh-on impossible to capture for an ordinary camera. This is mainly because of the fact that the amount of light entering the camera (and your eyes) is so low.
Your eye as a camera
So, as a quick re-cap, let’s take a look at how each of the components in your eyes are similar to that in a camera: