Light vs Camera and the Human Eye

eye vs camera

Light vs Camera Lenses

When it comes to light and photography, it’s helpful to understand some of the basic physics and relationship between light and camera lenses. The word “photography” was created from the Greek roots (phōtos, phōs, and graphé), which together means “drawing with light”. It is important to remember that light is the primary working tool of any photographer.

Light Rays

light prism color.

Light is the visible portion of the electromagnetic spectrum that starts from red (the weakest of rays) to violet (the strongest rays). Light rays from the sun are considered white because they contain all the colors of the spectrum.

Black is simply the absence of any color. When we place a prism in front of a white light ray, the prism will diffract (or separate) the ray into all the colors of the spectrum.

We have different labels for describing the rays we see. Here are a few basic ones:

  • Transmitted Rays: When you look at a stoplight, the top light is red, the middle is yellow, and the bottom light is green. That light is transmitted by putting a light source behind a colored filter.
  • Direct Rays: When you look directly into the sun, a camera’s flash unit, or a flashlight you are looking at direct light. The light you see is coming directly from the source.
  • Reflected Rays: When you look at anything, you can see that object because direct light is shining on it and being reflected back into your eyes.
  • Ambient Light: Think of ambient light as stray light – light rays that are being bounced around from all sorts of sources. If direct or reflected light on the subject is stronger your subject will appear clearer and less hazy.
  • Available Light: Available light simply means whatever light is present when not using a flash or other sources of light.

Light Refraction through a Prism

When we place a LENS in front of any ray, that lens will refract (bend) that ray.

animation of light through a prism.
Stop for a minute and watch this animation.
Light refraction through a prism.

Camera Lens

A camera lens is ground or molded transparent material (glass or plastic) that refracts light rays to form an image. A lens focuses light onto the sensor of a digital camera to create an image. It is also known as an optical or photographic lens.

Creating an Image

As a light ray enters the lens, it is refracted and exits the lens refracted in the same manner. Because of the geometric shape of the lens, light rays are refracted, so they form images. So when we place a lens in front of any light ray, the lens will refract or bend that ray.

the movement of rays from subject, lens, aperture, and film plane.

Being in focus involves moving the lens elements forward or backward until all the rays coming toward the camera from the subject meet at one point; the camera sensor. In the illustration above, you will see a point where the rays meet. That point is also called the film plane. At that point, all light rays of the subject must meet to accomplish sharp, focused pictures.


Light and the Human Eye

the structure of a human eye.

The human eye looks basically like the illustration. The lens at the left side of the eye focuses light rays onto the retina at the right. The retina converts light rays into electrical impulses that are sent to the brain. Our brain then tells us we are seeing a bit of light.

Cornea

The cornea is smooth and is clear as glass. It’s strong and it helps shield the rest of the eye from germs, dust, and other harmful matter (along with your eyelids, eye socket, tears, and sclera; the white part of the eye). The cornea is the eye’s outermost lens and it controls the amount of light into the eye. The Cornea behaves like the front of a camera lens. When light strikes the cornea, it bends (or refracts) incoming light onto the lens. The lens refocuses that light onto the retina.

Pupil

The pupil is the round opening in the center of the eye. The Iris and Pupil act work just like the aperture of a camera. The iris is a muscle which, when contracted, covers all but a small central portion of the lens, allows adjustable control of the quantity of light entering the eye so that the eye can work well in a wide range of viewing conditions, from dim to very bright light.

Retina

The Retina is the sensory layer that lines the very back of our eyes and it works similar to digital sensor in your camera. The retina has photoreceptor nerve cells that help change the light rays into electrical impulses and send them through the optic nerve to the brain where an image (of what we see) is finally received and perceived. Because of this reception and perception function, retina is, perhaps, the most important component of our eyes.

How the Human Eye Works – Animation Video

Just like the human eye, cameras have a lens in front of the sensor to capture light rays. Light rays enter through the lens to the digital sensor; which is sensitive to light.

Human Eye vs Camera

We found a great video that explains the difference and relationship between human eye and the camera. It runs just under 2 minutes.


The Characteristics of Light

Photographers are constantly talking about the quality of light (both good and bad). Light can be hard or soft, direct or indirect, natural or flash, and come from different angles. As you learn the Art of Photography, you will undoubtedly hear photographers refer to using “good light” in their photos. So what is good light?

There is no one good answer because it’s subjective. Good Light is just the right amount, quality, color, and angle of light a photographer needs to produce the desired image. For landscape photographers shooting in the early evening, it’s all about timing for the best light. The Golden Hour is the hour between sunset and nighttime when the light is diffused, soft, and colors can be vivid. This is in comparison to daylight which is harsh, leaving subjects looking flat and unflattering.

Light and The Photographer.

Types of Light

There are generally three types of light sources in photography;

  • Natural Light
  • Camera Flash Light
  • Studio Flash

Quality of Light

When photographers talk about the quality of light, they’re referring to the intensity of light;

  • Soft Light
  • Hard Light
  • Direct Light
  • Indirect Light

Angles of Light

The angle of light is the direction of your light source;

  • Front
  • Backlight
  • Sidelight
  • Reflected
  • Diffused (or dispersed)
  • Night (or twilight)

Read our detailed guide on 11 types of lighting and how to use them.

A Photographer’s Guide to Light

If you’re interested in learning more about light in photography, check out the following courses:

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