What does focal length scale mean?
Focal length, usually represented in millimeters (mm), is the basic description of a photographic lens. The longer the focal length, the narrower the angle of view and the higher the magnification. The shorter the focal length, the wider the angle of view and the lower the magnification.
How is focal length measured?
The primary measurement of a lens is its focal length. The focal length of a lens, expressed in millimeters, is the distance from the lens’s optical center (or nodal point) to the image plane in the camera (often illustrated by a “Φ” on the top plate of a camera body) when the lens is focused at infinity.
How do I determine the scale of a photo?
Calculating Distance and Area You simply measure the distance on the photo (photo distance) and multiply the distance by the scale factor. Remember that scale is always equal to the ratio of the photo distance to the ground distance. Example: The scale of an aerial photograph is 1:15,000.
What does 50mm focal length mean?
The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters (e.g., 28 mm, 50 mm, or 100 mm). The shorter the focal length (e.g. 18 mm), the wider the angle of view and the greater the area captured.
How do you find the focal length of a scale?
You can calculate the average scale of an unrectified air photo by solving the equation Sp = f / (H-havg), where f is the focal length of the camera, H is the flying height of the aircraft above mean sea level, and havg is the average elevation of the terrain.
How to calculate the scale of a photo?
You can also calculate air photo scale at a particular point by solving the equation Sp = f / (H-h), where f is the focal length of the camera, H is the flying height of the aircraft above mean sea level, and h is the elevation of the terrain at a given point.
What does the focal length of a camera tell you?
Lens focal length tells us the angle of view —how much of the scene will be captured—and the magnification —how large individual elements will be. The longer the focal length, the narrower the angle of view and the higher the magnification.
How is the scale used in digital cameras?
In digital cameras, the scale does not play any role in defining the image quality, as is the case with film-based camera. In digital cameras, we use the Ground Sampling Distance (GSD) to describe the resolution quality of the image while in film-based cameras we use the film scale.
Why does the air photo scale change with altitude?
Assuming that the aircraft carrying the camera maintains a constant flying height (which pilots of such aircraft try very hard to do), the distance between the camera and the ground varies along each flight path. This causes air photo scale to be larger where the terrain is higher and smaller where the terrain is lower.