Lens Focal Length: Normal, Short, Long, Special Lenses

  Lens focal length is the most important characteristic of a lens. One of the prime advantages of a single·lens reflex camera or a view camera is the interchangeability of its lenses; the reason photographers own more than one lens is so that they can change lens focal length. … PDF: Lens Focal Length, The Basic Difference Between Lenses   Normal Focal Length The Most Like Human Vision A lens of normal focal length, as you might expect from the name,  produces an image on film that seems normal when compared with human vision. The image includes about the same angle of view as the human eye Read more

Single-Lens Reflex (SLR) Camera

The 35mm Single Lens Reflex (SLR) camera is fundamentally a 45° hinged mirror set behind a lens which reflects the image up to a focusing screen on the camera top. As the shutter release is pressed the mirror flips up to: i) Form a seal under the focusing screen to prevent light from entering the camera through the viewing lens. ii) Move out of the way of the lens and film. When the mirror reaches the horizontal position it fires a focal plane shutter just in front of the film to make an exposure. Distances are arranged so that the Read more