# Shared Flashcard Set

## Details

Science and Theory Term 1 - 2016 Third Set
Fanshawe College - Photography- Level 1 Science and Theory
93
Photography
Not Applicable
12/27/2016

Term
 What Are The 3 Ways Light Interacts With Matter?
Definition
 Absorption   Reflection   Transmission
Term
 What is Absorption?
Definition
 When light strikes an object then disappears and takes on another form...   A black object such as a T-Shirt will absorb the light and turn it into heat. That's why you will feel hotter in a black shirt in the summer versus a white t-shirt, which will reflect the light.
Term
 What Are The Two Types of Reflection?
Definition
 Direct    Diffused
Term
 What is Direct Reflection?
Definition
 No scattering of the light. An example is a reflection in a mirror. Sometimes called “specular reflection”. Angle of incident equals the angle of reflection.
Term
 What is Diffused Reflection?
Definition
 Incident light is reflected from every part of a surface in many directions.
Term
 What is Transmission?
Definition
 When light passes completely through a material. For example, glass and water.
Term
 How Does Light Interact With Matter?
Definition
 Refraction    Deviation
Term
 What is Refraction?
Definition
 When a ray of light travels from one medium into another, its direction changes. This “bending” of the light is refraction. [image]
Term
 What are the Angles of Incident and Refraction?
Definition
 Angle of Incident is the angle at which light enters an object (like a glass of water) and Angle of Refraction is the angle at which the light bends once it has entered the object...   [image]
Term
 What Causes Refraction?
Definition
 It is the change in the speed of light when it passes from one medium to another.
Term
 What Does Normal Mean in Refraction?
Definition
 It is the path that is perpindicular to the surface.     [image]
Term
 What is the Refractive Index?
Definition
 This is how much the speed of light is reduced as it enters another medium. It tells you how much bending power a medium has.   Crown Glass : Refractive Index of 1.50    Flint Glass : Refractive Index of 1.60
Term
 What is Snell's Law?
Definition
 It is used to calculate the amount of bending that will take place.   (n1 sin i = n2 sin r)
Term
 What is Deviation?
Definition
 Angular change in direction of the emerging light ray compared to the incident light ray. OR How much the light changes direction once it leaves the medium.
Term
 What is the Difference Between Parallel and Non-Parallel Mediums With Regards to Deviation?
Definition
 With parallel sides (like a glass) there will be displacement but no deviation.   With Non-Parallel sides (such as a prism) there will be deviation.
Term
 What is Dispersion?
Definition
 When light splits up into its component parts as when light travels through a prism, and the different wavelengths separate to form a   spectrum. [image]
Term
 What is a Lens?
Definition
 A lens is a system of one or more pieces of glass with spherical surfaces, all of whose centres are on a common “optical axis”. [image]
Term
 What is a Simple Lens?
Definition
 It consists of a single piece of glass.
Term
 What is a Compound Lens?
Definition
 Consists of several glass components or lens elements, some of which are cemented together. [image]
Term
 What is a Positive Lens?
Definition
 Takes diverging light rays from a point source and uses refraction to bend the light toward a “focus point” forming a “real” image. Convex lenses (double and plano) are positive. Convergent (meniscus) lenses are positive. [image]
Term
 What is a Negative Lens?
Definition
 Incident light rays are diverged even more by refraction so that the light appears to originate from a virtual focus point. Concave lenses (double and plano) are negative lenses. Divergent (meniscus) are negative lenses. [image]
Term
 What are the 4 Lens Shapes?
Definition
 Convex   Concave   Plane   Meniscus
Term
 What is a Meniscus Lens?
Definition
 It is a lens that is concave on one side and convex on the other.
Term
 What are Retrofocal Lenses?
Definition
 They are sometimes called reversed telephoto.   They allow for a longer back focus distance.   Extra lens elements may reduce sharpness.   Extra glass is between the lens and the camera body.   [image]
Term
 What is a Telephoto Lens?
Definition
 Extra glass is in front of the lens.   Allows for longer focal distance.    Gives a narrow field of view and a magnified image.   [image]
Term
 What are Ray Drawings?
Definition
 They are a simple way to make predictions about an image formation.   [image]
Term
 What Does Lens Aberration Mean?
Definition
 Any problem that causes the failure of light rays to converge at one focus point or focal plane.
Term
 What is Chromatic Aberration?
Definition
 The inability of a lens to bring all the colours to a common focus. [image]
Term
 Which Wavelengths Refract More?
Definition
 Blue and Violet   They also focus closer to the lens.
Term
 What are Axial Chromatic Aberrations?
Definition
 When different wavelengths are focused at different distances from the lens along the lens axis.   [image]
Term
 What are Lateral Chromatic Aberrations?
Definition
 When wavelengths are focused at different positions in the focal plane...usually the corners.   [image]
Term
 What Happens If You Have Two Lens Elements Made of Two Different Types of Glass?
Definition
 Oner aberration will cancel out the other.
Term
 What is Achromatic Doublet?
Definition
 It uses Crown glass for the convergent lens and Flint glass for the divergent lens. (If the lens only uses one type of glass it cannot be achromatic)   [image]
Term
 What Else Can Be Used to Fix Chromatic Aberrations?
Definition
 Low dispersion glass.   Other materials with a lower refractive index   Flourite is one example.   It is very expensive.
Term
 What is an Achromatic Lens?
Definition
 It brings 2 colour regions to a common focus point.    Usually red and blue.
Term
 What is an Apochromatic Lens?
Definition
 A lens that is corrected to bring 3 colour regions to a common focus point.
Term
 What is a Spherical Aberration?
Definition
 When parallel rays of light do not focus on the same plane. A lens with a spherical surface causes the blurring of a point because it cannot bring all the light gathered from a single point to focus at a single point. The effect is worse further away from the optical axis ie. lenses with large diameters. [image]
Term
 Which Lenses are Especially Affected by Spherical Aberrations?
Definition
 Usually lenses with large apertures (fast lenses - small numbers for f#) and wide angle lenses.   The problem can be reduced by limiting the maximum aperture to 5.6
Term
 What Type of Lens Must be Used to Make Lenses With Large Apertures?
Definition
 Aspherical lenses must be used.   They are expensive to make.
Term
 What are Aspherical Lenses?
Definition
 A Lens having a free-curved surface which is not spherical. Can allow a larger useable aperture. [image]
Term
 What is a Floating Lens Element?
Definition
 Some lenses incorporate a set of floating elements that greatly improve close-up focusing. [image]
Term
 What is Coma?
Definition
 A type of spherical aberration. Occurs when rays strike the lens at an oblique angle and image points of the lens axis appear comet shaped. Soft focus further away from the axis. [image]
Term
 What is Astigmatism?
Definition
 A defect where horizontal lines and  vertical lines have different focal planes.   Not an issue along the lens axis. Gets worse further from the lens axis.   Larger apertures increase the effects of  this problem. [image]
Term
 Are Distortions and Diffraction Aberrrations?
Definition
 NO!!
Term
 Name Two Types of Distortion...
Definition
 Barrel   Pincushion
Term
 What is Barrel Distortion?
Definition
 Usually associated with wide angle lenses. Causes a bulgin in the image.   [image]
Term
 What is Pincushion Distortion?
Definition
 Often associated with telephoto zoom lenses.   Causes the image to look pinched.    [image]
Term
 What is Rectilinear Distortion?
Definition
 Caused by lenses designed to prevent barrel distortion. Keeps vertical lines straight, but in extreme wide-angle, the edges of the image appear unnaturally stretched. Also not an aberration. [image]
Term
 What is Diffraction?
Definition
 Refers to the bending, spreading and interference of waves passing through an aperture. In our case, light waves. [image]
Term
 What is An Airy Disc?
Definition
 An image of a “point source” is not a point but a circle of light.   The Airy disc is a finite size. [image]
Term
 What Makes an Airy Disc Diameter Smaller?
Definition
 Shorter wavelengths make the diameters smaller.
Term
 What Increases the Size of an Airy Disc Diameter?
Definition
 A smaller aperture makes the Airy Disc diameter larger.
Term
 At What F-Stops Does Diffraction Become a Noticeable Problem?
Definition
 At f-16, f-22, f-32 etc.
Term
 What Does MTF Stand For?
Definition
 Modulation Transfer Function (MTF)
Term
 What is the Importance of MTF?
Definition
 Indicates how well the lens can reproduce a likeness of a subject on on a sensor or film. Sometimes referred to as its resolving power.
Term
 What is Modulation?
Definition
 The reduction of contrast. A line pair pattern undergoes degradation as the spatial frequency increases. In other words the image pattern is degraded in contrast until the pattern cannot be distinguished. [image] The lines disappear and become a grey patch.
Term
 What are MTF Graphs?
Definition
 They show the sharpness of an imaging system or component. 1. Horizontal axis is the distance (mm) from the centre of the image towards one of the corners Vertical axis is contrast. (1=no contrast reduction)  2. Black lines: Max Aperture Blue lines: f/8 3. Solid Line: Sagittal target (S) Broken LIne: Meridional (M) (Tangential) 4. Bold Lines 10 lines/mm spatial frequency Thin Lines: 30 lines/mm spatial frequency [image]
Term
Definition
 Closer to "1" the better the contrast and resolving power.  -if 10 lines/mm (Bold) are.8 or higher, great lens -if 10 lines/mm (Bold) are .6 to .8 then considered good quality. -the closer the sagittal (solid) and meridional (broken) curves match, the lower the astigmatism and the better the background blur. [image]
Term
 When Should MTF Curves be Compared?
Definition
 Only to a lens with an identical or similar focal length.
Term
 What is an Entrance Pupil?
Definition
 This is the “image” of the aperture, as it appears when one looks through the front of the lens.
Term
 How do You Find the Entrance Pupil?
Definition
 By pivoting the lens at different pivot points while looking through the lens, or an image created by the lens. If the image does not appear to move, then you have found it.
Term
 What is the Signifigance of Finding the Entrance Pupil?
Definition
 No Parallax Point (NPP)
Term
 What is Parallax Error?
Definition
 If the camera is rotated along the axis of the tripod mount, then the images are taken with lens being at slightly different positions.
Term
 What is Considered a Normal Angle of View?
Definition
 52 degrees.   Meaning, it is an angle of view that appears natural to humans. It is also approximately the angle of view given by a “standard lens”.
Term
 What is a Standard Lens?
Definition
 A standard lens is one whose focal length is the same as the diagonal of the sensor or film frame.
Term
 How do You Find the Diagonal of a Lens?
Definition
 Trigonometry...Pythagorean theorem A(2)+B(2)=C(2) eg: 24mm by 36mm 24(2)+36(2)=C(2) 576+1296=C(2) 576+1296=1872 Sqare root of 1872 = 43  so 43mm Closest to 43mm is the normal lens...45mm or 50mm
Term
 What is Vignetting?
Definition
 Darkening of the edges of an image.
Term
 What is Optical Vignetting?
Definition
 Light from objects progressively off-axis will encounter more obstructions in the lens. This results in less “pencil rays” coming from a point source, the further off-axis, the less light travels through the lens from that source.
Term
 What Can Reduce Optical Vignetting?
Definition
 Stopping Down
Term
 What is Flare?
Definition
 When stray light (non-imageforming light) enters the lens.
Term
 What Does Flare Do?
Definition
 Degrades image clarity by reducing contrast.
Term
 What is Flare Caused By External Light?
Definition
 Light from outside the field of view that hits the front surface of the lens. This light bounces off the lens barrel and internal lens elements and eventually reaches the sensor. This is exposure from non image forming light.
Term
 What is Solar Flare?
Definition
 An obvious flare pattern that occurs when the sun is within or just outside the field of view. Creates repeating pattern of a ghost image of the lens aperture or diaphragm. (flare spots)
Term
 What are Solutions to Flare?
Definition
 Lens Shades   Lens Hoods   Bellows Lens Hood    Your Hand   A Card   Flare Buster
Term
 What is Image Forming Flare?
Definition
 Light that strikes a lens (or any surface) can be reflected, absorbed or refracted.
Term
 How Does Refracted Light Affect the Image?
Definition
 It forms the image, as it should.
Term
 What Effect Does Absorbed Light Have?
Definition
 It has no effect. It never reaches the sensor.
Term
 How Does Reflected Light Affect The Image?
Definition
 Some light is reflected away from the lens. No problem there. (minor light loss) Some light is reflected at each lens/air surface. This reflected light can create non-image flare. This flare can bring non-image forming light to the entire sensor. This results in a lower luminance range, or reduced contrast especially affecting the shadows in the image.
Term
 What is Bokeh?
Definition
 bo·keh bōˈkā/ noun PHOTOGRAPHY   the visual quality of the out-of-focus areas of a photographic image, especially as rendered by a particular lens. "a quick, visual survey of the foreground and background bokeh of a variety of lenses"
Term
 What Affects The Quality of Bokeh?
Definition
 The shape of the aperture.   -Better lenses often have more aperture blades, and those blades are often curved to give an aperture that's more circular. They produce a better bokeh -Very cheap cameras may use four- or even three-blade apertures resulting in square or triangular out-of-focus highlight-- not good bokeh.
Term
 What Are Mirror Lenses?
Definition
 A telephoto that is made with internal mirrors to achieve a long focal length in a smaller (shorter) physical sized lens. Incoming light is reflected forward by the first mirror, then a second mirror reflects it back towards the camera’s sensor.
Term
 What Are Ultravoilet (UV) Filters?
Definition
 Protects the front element of a lens from dust, dirt, moisture and potential scratches. High quality UV filters can be permanently mounted on lenses with a minimum impact on image quality.
Term
 What Are Neutral Density Filters?
Definition
 Used to reduce the illuminance by a known factor in cameras Useful when the brightness of the subject is still too high for the fastest shutter speed and the smallest aperture.
Term
 What Are The Characteristics of a Neutral Density Filter?
Definition
 • Used to reduce the amount of light reaching the sensor • Neutral means that it allows equal amounts RGB wavelengths to get through, (or equal amounts filtered out) • In other words… no colour balance shift. (Neutral) • Known “factors” 1 stop, 2 stops, 4 stops, 8 stops etc.
Term
 What Do Neutral Density Filters Allow You To Do?
Definition
 • Allow for wider apertures when there is too much light, helps decrease depth of field • Allow for slower shutter speeds when trying to capture a moving subject and you want to show that movement. (waterfall, cars, traffic, trees etc.)
Term
 What Are Filter Factors?
Definition
 A multiplying number that specifies the change in exposure necessary to compensate for the light loss caused by the filter.
Term
 When Do You Use a Gradient Filter?
Definition
 This filter is used outdoors when the  dynamic range between the sky and the ground is greater than the dynamic range of the sensor or film
Term
 What Are Advantages to Large Format Cameras?
Definition
 •All the parts move independent of each other, so you can move the lens and the film plane separately •These movements allow for more control of focus, distortion and perspective.
Term
 What Are the Disadvantages to a Large Format Camera?
Definition
 •Requires a tripod •Bulky, heavy •slow to set-up •The image on the ground glass is dark so you need a way to use a focusing cloth (dark cloth) •There is no pentaprism, so the image on the ground glass is upside down and reversed left to right
Term
 What Are The Movements of Large Format Cameras?
Definition
 •Rise and Fall •Shift left and right •Tilts up and down •Swing toward left and right
Term
 What is The Scheimpflug Principle?
Definition
 If the camera’s lens plane and film plane are not parallel, then the plane of focus will meet those two planes in a line
Term
 What Problems Can Large Format Cameras Correct?
Definition
 •Correcting for converging lines •Keeping lines vertical (especially in architecture and commercial subjects)
Term
 How Are Tilt Shift Lenses Similar To Large Format Cameras?
Definition
 They mimic the movements   •Rise and Fall •Shift left and right •Tilts up and down •Swing toward left and right
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