These slides contain some important and fundamentals ideas about Aerial Photographic Flims...

1. AERIAL PHOTOGRAPHIC FILM
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2. INTRODUCTION
Film is usually exposed in camera mounted in an aircraft that is moving
rapidly fast. Fortunately, films made especially for aerial photography can
stop action and yield high-quality aerial photography if,,
1.The proper film/filter combination is used
2.The aperture opening is appropriate
3.The length of the exposure is correct.
In film photography, the resulting image can be either black and white or
colour, depending on the film used
Black and white photographs are typically exposed on negative film from
which positive paper prints are made.
Colour image are typically recoded directly on film, which is processed to a
positive transparency.

3. Silver Halide Crystal Grain Size, density and shape
Silver Halide Crystal is the main properties of photographic film. Generalized the cross section
of photographic film has three layers:
1.Emulsion layer: this layer is sensitive to light. And it’s composed of Silver Halide
Grain, it’s determine how much is it sensitive of light. The Emulsion properties is
depends on the numbers, size and density of silver halide crystal.
If we compare between two films: film “A” has 10 crystals and film “B” has 7 crystal.
As grain size increase, the total number of grains in the per unit distance decrease.
Therefore film “B” is faster than film “A”, because it requires less light for proper
exposure.
As sensitivity and grain size increase the resulting image becomes more courser and
resolution may be reduced.
The faster films is used when the object are moving rapidly across the film plane.

4. 2. Base:
Remaining light reach this layer.
3. Anti-halation layer:
last total remaining light absorbed this layer.
Plate: negative photographic films

5. For example, a non turbid ocean water and a sandy
beach with no vegetation.
We know that, the film silver halide crystals are
sensitive to blue, green and red light.
The non turbid ocean water would absorbed much or
the incident light of visible range. Conversely, the
sandy beach reflect most of the radiant flux. This
energy collected by the optics of the camera lens and
exposed the film.
In this example there was sufficient energy to expose
the silver halide crystal on the left side of the film but
the insufficient energy to expose the crystal on the
right side of the film. And formed latent image. To
turn the latent image on the emulsion into a
negative, it must be developed.
Fig: A diagrammatic presentation of how a black-
white negative of an ocean beach scene is exposed
and developed.

6. A white light is transmitted through the negative,
passed through the enlarger lens and onto
photographic paper that has its own silver halide
crystal sensitivity.
In this case, the dense(dark) beach area on the
negative allows very little radiant flux to pass through
the negative while the clear(ocean) area on the
negative allows a lot of radiant flux to pass through it.
And this energy is focused through the lens onto the
undeveloped photographic paper. And forming a
latent image on the photographic paper.
After development, the exposed ocean area become
dark and sand beach area becomes light on the paper
print.
Fig: how a positive black-white print of the ocean beach scene is
produced from a developed negative.
(source: Jensen,2004)

7. Radiometric Characteristics of Black-White Films
1. Transmittance
Transmittance is the ability of a portion of a developed film to
pass light.
A black portion of the film may transmit no light, while a clear
portion of the film may transmit almost 100% of the incident
light
Tij=light passing through the film/total incident light
2. Opacity
There is an inverse relationship between
transmittance and Opacity
Oij=1/Tij
Where,
1=total incident light
Tij=transmittance

8. 3. Density
Density is proportional to Opacity, if the opacity is high then
the density is also high, and low transmitted.
Dij=log10 Oij=log(1/Tij)
Table: relationship between Transmittance, opacity and Density.

9. Characteristics of curve
In this characteristics curves represents two
hypothetical black-white negative films, X and Y are
shown in these D log E curves. Where the film density
is plotted on the Y axis and total exposure of the film is
plotted on the x axis
In these curve consisting of three part like; toe,
straight line or linear section and shoulder.
The curve is provide a important information about
film emulsion.
In these films a part has no exposure but there is some
density already present, this area is called “fog”. And
the unexposed density area is called “Gross fog”. The
gross fog is located in the lower position of the toe
and labeled Dmin.
Fig: characteristics curve of two hypothetical black-
white films. (source: Jensen,2004)

10. a to b in this portion is called “toe”.
And the b to c portion where is the length of the exposure increases and density also increase this
portion is called linear or straight line part. High quality aerial photography may be obtained if the
exposure is made in the linear portion.
Length of the exposure time increase from c to d and the density increase but decreasing the
curvilinear rate, this part is called ‘shoulder’.
The maximum density labeled of this curve is called Dmax. This is the overexposed area.
The slope of the linear section in this curve is called gumma, the greater slope is indicate the
higher value of gumma and the higher contrast of the film.
In this two X Y curve have significantly different gummas value. Film X have a greater range of
density(2.2) and film Y would only yield a density approxly 0.5 at this same exposure. So the film X
is provide a full range of grey tone and the film Y not provide a full range of grey tone.
Film X is the faster film, it requires a shorter exposure time. Larger silver halide crystal and low
spatial resolution.
And film Y is the slower film, it requires a longer exposure time, smaller silver halide crystal and
high spatial resolution with subtle greyscale information.

11. Film Resolution
The film Resolution measured by the two process, these are discuss below:
1. Measure the film resolving power by standard test chart
It consists of groups of three parallel lines
separated by space equal to the width of lines.
The resolving power is expressed in units of lines
per millimetre and some times referred to in
unites of “line pairs” per millimetre.
The “line pair” refers to a line (white) and
space(black) of equal width.
Resolving power is specified at a particular
contrast ratio between the lines and their
background. Resolution is very strongly
influenced by contrast.
Fig:USAF resolving power test chart.
Source: Lillesand and kiefer,2014.

12. 2. Film’s modulation transfer function
In this method a scanning densitometer is used to scan across
the image of a series of “square wave” test patterns..
An ideal film would exactly record not only the brightness
variation (modulation) but also the distinct edges in the
pattern.
Fig: film’s modulation transfer function
(source: Lillesand and kiefer,2014)

13. Ground resolution distance
Example:
A photograph at a scale of 1:50,000 taken with a system having a
dynamic resolution of 40lines/mm. would have a ground resolution
distance of:
GRD=reciprocal of image scale/system resolution
GRD=50,000/40
=1250mm. Or, 1.25m.
Fig: modulation transfer function curve
Source: Lillesand and kiefer,2014.

14. Filters
Filter are used to reduced/minimize/removed the unwanted
scattering/reflection/radiation from a scene before the light reaches the
film in the camera.
Types:
1. Haze filter
Removed the haze, clouds and fog etc.
2. Band pass filter
For use a particular band
i) Low pass filter
Passing only the short/low wave length
ii) High pass filter
Passing only the long wave length.
3. Interference filter
Removed of the any one particular
band.
4.Antivirnattive filter
Used to equality of light of any
image
5. Yellow/blue blocking filter
For remove the blue colour

15. Colour Mixing Theory
Additive color is a method to create color by mixing a number of
different light colors, with shades of red, green, and blue being the most
common primary colors used in additive color system.
GREEN+RED=YELLOW
BLUE+GREEN=CYAN
BLUE+RED=MEGENTA
BLUE+ GREEN+RED=WHITE
 BLACK light is the absence of all these colours
 Yellow, magenta and cyan are refers to as
complementary colour
Additively combination: Fig: additive colour process

16. Subtractive colour theory is based on the use of the complementary colour dyes–
Yellow, Magenta and Cyan.
Magenta & Cyan dyes filter=only perceived Blue light
Yellow & Cyan dyes filter=only perceived the Green light
Yellow & Magenta dyes filter=only perceived Red light
Yellow, Magenta, Cyan dyes filter=not perceive any colour=appear Black
Yellow dye filter subtract Blue light and passing the Green and Red light
Magenta dye filter subtract Green light and passing the Blue and Red light
Cyan dye filter subtract Red light and passing the Blue and green light
Projected the white light onto a translucent filter:
Superimposition:

17. Colour Film
Fig: cross section of colour
film
Fig: colour formation with colour film (adopted from Eastman Kodak
Company,1992
Source: Lillesand and kiefer,2014.

18. Fig: cross section of colour
infrared film
Fig: colour formation with colour infrared film
(adopted from Eastman Kodak Company,1992)
Source: Lillesand and kiefer,2014.
Colour Infrared Film

19. References:

20. Thank You