Certification
Letters
of certification are typically used
in legal proceedings. They authenticate the photo or photos in
question by explicitly stating many particulars,
usually including such information as the original photographer, date
the photo was taken, the approximate negative's scale, etc.
Also, a letter of certification often contains a statement that no
intentional alterations have been made to the print, signed by a
representative of the photography company. Normally, a letter of
certification will come attached to the photo
product (or, in the case of those sources that will also certify
DIGITAL IMAGEs, it may be attached to a printed representation of the
image).
Note: Due to the more easily-modifiable nature of DIGITAL IMAGES, many sources will not offer letters of certification for them.
Contact Print
A
contact print is the
equivalent of a proof, just like you might get from a portrait
photographer. Therefore the print is the same size as the original
NEGATIVE. Contact prints are made by putting the paper on the NEGATIVE
(i. e. in contact with the NEGATIVE) and exposing the image
directly, rather than projecting the image through a lens. Aerial
photography is typically shot using large cameras with 9 inch square
NEGATIVEs. Therefore a contact print is usually about 9"x9"
and is useful as a final product just like a portrait photographer's
8"x10" print. Due to the process required to make
photographic paper, contact prints cannot reproduce all the fine
details originally captured in the NEGATIVE and so it might be
necessary to enlarge or "blow up" the photo to see the
desired details.
Diapositive
A
"diapositive" is a photo that is chemically developed in
the same manner that a contact print is produced. It differs from a
contact print, however, in that it is printed on a transparent sheet of plastic
rather than photographic paper. It is the aerial photography
equivalent of a slide. It appears similar to a NEGATIVE, but the
image is normal, i. e. the colors aren't reversed. Because the
transparent sheet is made using almost the same technique used in
camera film, diapositives can almost exactly reproduce the fine
details originally captured in a NEGATIVE. They are typically used
for examination of sites, such as map making. They can also be used
with overhead projectors in presentations showing enlarged portions
of an image on a wall similar to conventional slides. Also called
"film positives" or "photo transparencies".
Digital Image
An increasing amount of aerial photography is being taken
with digital aerial cameras instead of traditional film cameras. Like standard consumer handheld
digital cameras, these cameras do not produce film-based NEGATIVEs, but
instead record the image as a computer file.
Also, NEGATIVEs taken with film-based cameras can be
scanned with special large format scanners
and recorded as a computer image file with results similar to (usually
superior
to) photos taken with digital cameras. Digital images can be
printed out on standard
computer printers or printed with a special process that produces
traditional chemically-produced prints. Digital images can also
be viewed on
a computer screen instead of or in addition to being printed.
Sometimes conditions such as lost or destroyed NEGATIVEs force digital
images to be produced from existing paper prints. Also called
"scans" or "digital scans".
Digital Print
Instead of a photo being developed from a
negative by a chemical process, a digital print is a photo produced
from a computer image file that has been made either by scanning a
negative
(or transparency), or by having been originally taken with a digital
camera. The quality of digital prints varies depending upon the
equipment used, the resolution the picture was scanned or
shot at, and the type of printing equipment.
When NAR produces
a digital print from a negative or
transparency, we can scan at resolutions from 1200 Dots Per Inch to
2000 DPI. The printing equipment we use has the ability to print
a 1:1 scale photo (i.e. at its original size, not an enlargement) on
photographic paper that can be viewed under magnifications up to 12X
without any appreciable "pixelation" (digital degradation). These
prints, therefore, are equal in quality to a standard,
chemically-developed print.
Duplicate Negative
A copy of the original NEGATIVE Production of NEGATIVEs is done
through standard chemical photographic processing methods. These
methods are not digital, but analog in nature and therefore can't
produce exact copies of the original NEGATIVE. Proper
duplication techniques, however, produce nearly exact copies of the
original NEGATIVE and are considered identical for all but the most
exacting
examinations.
Enlargement Print
A print made by magnifying portions of or the entire original image is
commonly known as a "blow-up" and more correctly referred to as an
"enlargement print" (or "enlargement" for short). Aerial
photography is taken with "large-format" cameras. The difference
between large formats and small or standard formats is the size of the
original image that is captured. In traditional,
chemically-produced photography, this is the difference in the size of
the NEGATIVEs. A standard small format camera typically takes
pictures using 35mm (approx. 1.4 inch) NEGATIVES. In contrast, a
large-format aerial photography camera typically takes pictures using
229mm (approx. 9 inch) NEGATIVES. It is due to the camera
lens' dense packing of imagery in the NEGATIVE that allows very
detailed images to be captured on such relatively small NEGATIVE sizes.
The size of the NEGATIVE tends to be somewhat hidden
to the small-format photography customer. Typically the customer
thinks of the standard print size as 4"X6" and a blow-up or enlargement
as a larger image, such as 8"X10". In reality,
any print
that is not the size of the NEGATIVE (say 35mm in size) is an
enlargement. Prints this size are not very useful in small-format
photography (approx. 1.4 inch). But, in large formats, such as
aerial photography, an unenlarged print is 229mm square (9"X9") and
appears to be similar to a small format camera's 8"X10" enlargement.
Since small-format, especially 35mm, photography is
more common than large format, the apparent similarity between 8"X10"
enlargements and 9"X9" "CONTACT PRINTs" often confuses customers into
thinking they have received an enlargement. In fact, just as a
35mm NEGATIVE can produce clear enlargements at up to 8 times (the
number of times an 8"X10" print is blown-up to) so to can the 229mm
negative of the aerial camera. In fact, it's possible to enlarge
the entire aerial photograph 5X to a size of approximately 4 feet
square. Smaller portions of an aerial photograph can commonly be
enlarged as much as 15 to 20 times.
The advent of digital photography into the aerial
photography field has broadened the number of methods, product types,
and levels of quality available to the customer. For purposes of
discussion, we classify the clarity of detail which can
be seen in a given enlargement print into 3 grades:
Presentation, Review, and Examination.
An
individual photo is often called a "frame".
Identification Bar
A
line of data, usually printed along an outer edge of a photo, which
lists information that is used to identify the photo. The
identification bar will usually list the photo's roll and frame
number, and will often times also include other useful data, such as
the original project code of the company that shot or commissioned
the taking of the photos, and even the photo's scale.
This information can be very important when trying to locate the
current owner of a given photo or to re-order a new copy of a photo
already known to exist. Many times the data listed on an
identification bar is all that is required to locate and order a new
copy of a given photo.
Monoscopic Photography
Monoscopic photography is the opposite of stereo photography. Instead
of taking pictures with a high degree of STEREO OVERLAP, as with STEREO
PHOTOGRAPHY, monoscopic
photos are taken far enough apart that there is almost no amount of
shared ground area (STEREO OVERLAP)
between one photo and the next along the same FLIGHT LINE.
Monoscopic
coverage, therefore, cannot be used to see areas in 3-dimensions,
because it lacks the two different perspectives that combine to create
the illusion of depth which the STEREO OVERLAP of STEREO PHOTOGRAPHY
provides.
SEE Stereo
Photography for a more detailed explanation of how stereoscopic
photography works.
Negative
Briefly stated, a negative is the original
print made in traditional photography on a transparency as a reversed
version of the image. A more detailed description requires a
little background first.
Traditional photography, as opposed to digital
photography, uses a chemical process to capture images and store them
on a specially-coated surface. The chemicals respond to light by
absorbing it, becoming dark as a result. The brighter the light
the chemical is exposed to, the darker the chemicals in the coating
become. Therefore, the captured image looks exactly the opposite
from the original source (i. e. shadows are light, and light sources
are dark). The original image is called a "positive" image and
the opposite image is called a "negative" image, just like in
arithmetic where a negative number is the opposite of the positive
number. Photographers want to show what the real world looked
like at the time the picture was taken and so the positive image is the
important one. The negative image proved to be a useful method of
achieving this when making multiple copies of the photo. If a
transparent surface, such as glass or plastic, was used to capture the
negative image, passing light through the negative image onto another
chemically-coated surface, such as a piece of paper, would produce a
positive image (i. e. the light shadows of the negative image are now
dark again.) Most traditional photography, and therefore
virtually all historical aerial photography, was taken in negative
form.
Negative Scale
SEE Scale, Photo Scale, Print Scale, or Negative Scale for a full explanation.
Photo Scale
SEE Scale, Photo Scale, Print Scale, or Negative Scale for a full explanation.
Photo Transparency
Another term used for a
DIAPOSITIVE.
Print Scale
SEE Scale, Photo Scale, Print Scale, or Negative Scale for a full explanation.
Scale, Photo Scale, Print Scale, or Negative Scale
Photo scale (often simply referred to as
"scale") is a general term used to refer to the size of objects
depicted in a photo image compared to the actual size of the object in
the real world. Scales are normally listed in either a standard
ratio such as 1:20,000 (meaning 1 unit measured on the photo represents
20,000 units in the real world) or in inches-to-feet form such as
1"=1600' (meaning 1 inch measured on the photo represents 1600 feet in
the real world). Therefore, a standard 9" x 9" square aerial photo at a
scale of 1"=2000' shows an area
18,000' (about 3.40
miles) wide by 18,000' long.
As an
example of how to use scales, if a building is 500 feet long and the scale of the photo is listed as 1"=2000',
then the building depicted in this photo would
be 1/4 of an inch long because 500' is 1/4 of 2000', so the depiction is 1/4 of 1 inch.
Photo scales are also called "print scales" or
"negative scales" when a particular photo image is being referred to in
order to be more specific. A negative scale
means the scale the photo was originally taken at. So, the scale
is the measure of objects in the image's NEGATIVE compared to the real
world. This differs from the print scale at times when the print is a blow-up (see ENLARGEMENT PRINT). It
is almost always possible to have enlargements, or "blow-ups", made
that will make objects in the photo larger and easier to see.
When an enlargement is made, the scale of the photo changes based on how
much the photo was enlarged. Because of this, the print scale is the measure of objects in a print made from the image's NEGATIVE compared to the real world.
So if a 10X enlargement
was made from the NEGATIVE in our above example with the 500 foot long
building, the print scale would become 1"=200', and the depiction
of the building would become 2 1/2 inches long.
Stereo Mate
A single photo which shares a portion
of STEREO OVERLAP with
another photo to produce a STEREO PAIR.
SEE Stereo
Photography for a more detailed explanation.
Stereo Overlap
The portion of coverage shared by a pair of
stereoscopic photos, in which each portion covers the same area of
ground from slightly different angles.
SEE Stereo
Photography for a more
detailed explanation.
Stereo Pair
A set of two stereoscopic photos that share
the same portion of STEREO OVERLAP.
SEE Stereo
Photography for a more
detailed explanation.
Stereo Photography
Stereoscopic photography, or "stereo
photography", is photography that is taken so that each photo shares a
portion of coverage with the next photo along a FLIGHT LINE. In
this way, the
area which one photo shares with the next is taken from a slightly
different angle. When properly viewed, the two different angles combine
to create an illusion of depth in the photography.
Stereoscopic Photography
SEE Stereo
Photography for a full explanation.
Stereo
Viewer
A device that is used to assist in
properly
viewing the 3-D effect of the STEREO OVERLAP of a STEREO PAIR.
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