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

Additional Photography Flashcards

 


 

Cards

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
Reading an MTF Graph...
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
 
  1. 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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