Lens 104

You might hear the term “focal length” thrown about. What is focal length?

“The focal length of a lens determines the size of the image of your subject that the lens forms on the camera’s sensor or film.”


“The focal length is the distance from the optical center of the lens to the imaging sensor when the lens if focused at infinity. “


If you what a more detail explanation, or the math behind focal length calculations, you can head over to wikipedia

Simply put, the longer your focal length, the larger the image of the subject will be. A 400mm lens will produce and image 4x higher and wider than a 100mm lens.

When you throw in aperture you really start to get the “picture”…sorry, bad pun.

Remember, we aren’t just interested in how much light enters the camera, but also, how much light actually reaches the sensor. The closer the lens is to the sensor, the more intense the light; the farther the lens is from the sensor, the less intense the light reaching it will be.

So, wrapping up, the focal length of a lens determines how much or how little of a scene you can capture. A longer focal length produces a larger image. Using a lens with a long focal point may require you to move away to capture more of the image; or change to a lens with a shorter focal length.


Thanks for reading, keep on shooting, and, as always I look forward to your continued support.

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