LENS Flashcards
___ is a system of one or more pieces of glass bounded by spherical surfaces which is at a common axis. Common Axis is also known as ___.
Lens
Lens Axis
What are the 2 main types of lens according to shape
Convex/ Positive/ Convergent Lens
Concave/ Negative/Biconcave Lens
CONVEX LENS
a. BENDING OF LIGHT:
b. LENS:
c. IMAGE PRODUCED:
d. Used/Not used in Police or Forensic Photography
a. Towards each other
b. Thicker center and Thinner sides
c. Real Image
d. Used in Police Photography
CONCAVE LENS
a. BENDING OF LIGHT:
b. LENS:
c. IMAGE PRODUCED:
d. Used/Not used in Police or Forensic Photography
a. Away from each other
b. Thinner center while Thicker sides
c. Virtual image
d. Not used
What is the picture angle of the human eye that is similar to the normal lens of camera (35mm to 70 mm)?
45 degrees to 75 degrees
One with a focal length equal to the diagonal measure of the image area. It is usually standard equipment on a camera.
Normal Lens
Normal Lens, Wide Angle Lens, and Telephoto lens is used in what instances?
Normal Lens- mug shots
Wide Angle Lens- confined or restricted spaces
Telephoto Lens- surveillance or casing
It has a SHORTER focal length than the normal lens and as a result, it covers a picture angle 60° wider than normal lens. It enables photographing a widely extended scene from a close proximity or within a confined area.
Wide angle lens
It has a longer focal length and provides a close-up image of a distant subject. In contrast to the wide angle lens, the telephoto covers a SMALLER FOV and SHALLOW DOF.
Telephoto lens
This is usually found in simple or box camera comprises a single piece of glass with one side convex and other side concave. It is uncorrected lens and therefore suffers from inherent defects of lenses.
Simple Miniscus Lens
Simple Miniscus Lens came from the Greek word meaning ___.
“a little crescent moon”
It is a COMBINATION OF TWO ACHROMATIC LENS with almost the same focal length producing neutral colors. This is corrected from some kind of lens defect but not an astigmatism defect.
Rapid Rectilinear Lens
Rapid Rectilinear lens is also known as ___ and was invented by ____.
APLANAT Lens- John Henry Dallmayer
A lens which is free from astigmatism or other types of lens defect.
Anastigmatic Lens
A lens which is partly corrected from chromatic aberration.
Achromatic Lens
A saucer-corrected lens for astigmatism. It has a better color correction and has the ability to produce the best definition of image in the photographs.
Process Lens
______ lens used in all fixed focus camera. Basically, it has a SHORT FOCAL LENGTH and GREATER DOF. It is used in __ photography.
Fixed Focus Lens - indoor sports photography
What are the 2 special types of lens?
Macro Lens
Zoom Lens
Macro Lens came from the Greek word __ meaning ___.
Macro- “enlarge”
Designed with EXTENDED FOCUSING CAPABILITIES to shoot few inches from a subject.
Macro Lens
Allows quick adjustment to give a WIDE or NARROW FOV.
It can be moved back and forth while other elements stay in place which gives the same effect as if the camera itself was moving towards or away from the subject.
The subject is close to the lens.
Zoom Lens
These are lens defects or problems.
Optical Aberrations
It is termed as without color or the inability to transmit light rays to spectrum of colors.
chromatic
This is a defect that causes images to be blurred.
Astigmatism
____ is the focusing at different points of rays passing through different parts of spherical lens.
Cause:
Result:
Spherical Aberration
Cause: light hitting the lens’ outer part is BENT MORE SHARPLY which FOCUSED SOONER
Result: Blurred Image
The failure of different colored light rays to focus after passing through a lens, focusing of light of different colors at different points resulting in a blurred image. In ___, COLORED FRINGES surround the image because light of different colors is brought to different focal points by a lens.
e.g. prints in a newspaper
Chromatic Aberration
Cause: Light rays passed through the lens didn’t focus causing color fringes
Result: Blurred Image
The ability of the lens to bring horizontal and vertical lines in the subject to the same plane of focus in the image. It occurs at the EDGE OF IMAGE, the image appears elliptical or cone-shaped because of an irregularity in the curvature of the lens.
Astigmatism
It occurs when LIGHT FALLING OBLIQUELY on the lens and passing through different circular zones is brought to a focus at different distances from the film plane.
A spot of light appears to HAVE TAIL RATHER LIKE A COMET.
Coma
A curved, concave or saucer shaped image of an object which has a flat surface. The image distance is different for different points of the object due to their DIFFERENT DISTANCE FROM THE AXIS.
Curvature of Field
Inability to produce the SAME ENLARGEMENT in the image formed by the edges of the lens as in that part formed by the center of the lens.
Distortion
This is the type of distortion where the outer edges is wide while the center is narrow.
Concave or Pincushion Distortion
This is a type of distortion where the outer edges is bulged while the center is wide.
Convex or Barrel Distortion
A result of DOUBLE REFLECTION FROM INNER LENS SURFACE. It exhibits self as a misty, hazy or cloudy semi-circular path of light.
Flare or Optical flare
Bright spot on the film from WORN SHINY PARTS of the lens such as the stops, shutter, lens mount or from inside the camera itself.
Mechanical Flare
Most corrected lenses are coated with a substance which will reduce one type of flare and which will also increase the optics inability to transmit light.
Light loss
____ is actually a process helpful in diminishing flares but when used excessively will lead to ___.
Coating - light loss
It can be reduced or eliminated by using the PROPER LENS SHADE placed on the front of the lens or shield.
Stray light
This is a concept that enables how much light to see in the lens and it is DEPENDENT TO FOCAL LENGTH.
Field of View (FOV)
This is where light rays meet.
Focal Point or Focus
This is the distance between the center of the lens and the focal point. It determines how long.
Focal length
