Tuesday, October 22, 2013

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How to Determine Camera Focal Length

Focal length is defined as the distance from the middle of the lens to its focal point. It's the distance from the lens to the image pickup device (film in the old days and a sensor chip today). It's based on focusing at infinity. The image distance, which is the distance between the lens and the image pickup device is added to the object distance, which is the distance between the lens and the object. The distances change as you focus--lenses grow longer as you turn the focus ring--consequently that figure changes.

Instructions

    1

    Take a look at the lens barrel. The focal length will be displayed in millimeters (mm). Make a mental note of the one or two numbers you see. For example, 55mm or 28-105mm.

    2

    Apply the focal length multiplier to get the true focal length if you are using a film lens on a digital camera. The multiplier will be in your camera instructions. An image capture device's physical size determines the multiplier. If the image capture device is full-frame--the size of an old 35mm film then the multiplier is 1.

    3

    Refer to the following guide to determine the lens use for a film single lens reflex camera (SLR.) A focal length less than 50mm is a focal length for wide-angle use. The focal length is usually 18mm, 20mm, 28mm or 35mm. A normal lens is 50mm or 55mm and a telephoto lens is usually 90mm, 135mm, 200mm or 300mm.

    4

    Set up the camera. Use a long lens, a lens with a long focal length, to take a picture of a small subject at a great distance---say a 300mm lens. Use a short focal length lens to take a wide-angle shot, say an 18mm lens. And use a medium focal length lens---say 50mm for regular shots.


How to Determine Camera Focal Length

Focal length is defined as the distance from the middle of the lens to its focal point. It's the distance from the lens to the image pickup device (film in the old days and a sensor chip today). It's based on focusing at infinity. The image distance, which is the distance between the lens and the image pickup device is added to the object distance, which is the distance between the lens and the object. The distances change as you focus--lenses grow longer as you turn the focus ring--consequently that figure changes.

Instructions

    1

    Take a look at the lens barrel. The focal length will be displayed in millimeters (mm). Make a mental note of the one or two numbers you see. For example, 55mm or 28-105mm.

    2

    Apply the focal length multiplier to get the true focal length if you are using a film lens on a digital camera. The multiplier will be in your camera instructions. An image capture device's physical size determines the multiplier. If the image capture device is full-frame--the size of an old 35mm film then the multiplier is 1.

    3

    Refer to the following guide to determine the lens use for a film single lens reflex camera (SLR.) A focal length less than 50mm is a focal length for wide-angle use. The focal length is usually 18mm, 20mm, 28mm or 35mm. A normal lens is 50mm or 55mm and a telephoto lens is usually 90mm, 135mm, 200mm or 300mm.

    4

    Set up the camera. Use a long lens, a lens with a long focal length, to take a picture of a small subject at a great distance---say a 300mm lens. Use a short focal length lens to take a wide-angle shot, say an 18mm lens.

    Enhance your photography skill,The Top Secret Photography Techniques

    . And use a medium focal length lens---say 50mm for regular shots.



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