Lecture 7

Question 1

Apeature or f-stop

Answer 1

determines the amount of light that hits the sensor

• ration of camera lens focal length (f) to the diameter of the lens opening (d) is known as f-stop (f/d)
• shutter speed or exposure time determines the duration for which light hits the sensor
• the two together determine the totoal light that reaches the sensor

Question 2

Camera components compared with the eye

Answer 2

see slide

Question 3

Film resolution

Answer 3

defined as lines per mm
* resolution depends on target contrast
* high target contrast --> large density difference between bright and dark, and vice versa 
* Kodak panchromatic films
=high contrast -- 400 lines/mm
=low contrast -- 125 lines/mm

Question 4

Ground resolution

Answer 4

Rg = Rsf/H

Rg = ground resolution
Rs = system resolution (film-camera-lens)
f = focal length (mm)
H= altitude

Question 5

Conventional lenses have a short-wave cutoff at 350 nm–why?

Answer 5

Because we don’t want a saturation in blue

Question 6

How does color film work?

Answer 6

• Records energy in the visible region of EM
• UV radiation is cut by haze filter (e.g. Kodak HF3)
• At least 3 photosensitive layers
• Also a yellow filter (filters out yellow so it doesn’t reach lower levels)

Haze filter
Blue-sensitive layer
Yellow filter
Green-sensitive layer
Red-sensitive layer
Base
Backing

Question 7

Blue-sensitive film

Answer 7

• affected by x-rays, gamma rays, UV, violet, and blue radiation
• insensitive to other wavelengths

Question 8

Orthochromatic film

Answer 8

blue and green sensitive (to ~600 nm)

Question 9

Panchromatic film

Answer 9

sensitive to red, green and blue

extended red sensitivity to reduce atmospheric haze

Question 10

Infrared film

Answer 10

• originally developed during WWII to increase sensitivity of films
• sensitivity in addition to panchromatic is extended to 900 nm

Question 11

newton (1666) sptrum

Answer 11

found that white can be dispersed into a spectrum, red,, oranges, yellow, green, blue, indigo, violet

Question 12

Types of filters

Answer 12

filters out certain region of EMR before reaches film plane
Examples:
* yellow filter=filters UV and blue, decreases atmospheric haze
* red filters, absorbs UV, blue, and green
* Absorbs UV, blue, green red. only NIR will be recorded, true infrared

Question 13

Additive colors

Answer 13

• refers to the combination of light from multiple sources at specific wavelengths
• used in remote sensing, and on computer monitors, etc

Study additive diagram–yellow means blue absorbed, and red and green reflected

Very important for understanding false color, where colors are assigned to bands

Question 14

Additive color theory

Answer 14

• blue green and red are primary colors

* yellow magenta and cyan are the complementary colors

Question 15

Subtractive colors

Answer 15

referes to the removal of light from a source

• mixing paints
• filters
• based on complementary colors (yellow, magenta, cyan)

Question 16

visual interpretation advantages

Answer 16

• low investment
• simple method
• uses brightness and spatial content of the image
• builds upon photo interpretation experience
• includes a wide variety of criteria

Question 17

Visual interpretation disadvantages

Answer 17

influenced by interpreter’s subjectivity

Question 18

Learn hierarchical organization of visual interpretation

Answer 18

see slide