Microfilm, Microform, Types and Techniques
Not to be confused with photomicrography,
Microphotography involves taking photographs on very small film to produce
small images that can only be viewed when magnified. Whereas photomicrography simply
involves taking pictures (photographs) using a microscope, Microphotography is
the process through which the size of a photograph is reduced so that it can
only be viewed using a microscope. Because of the technique allows for a
significant reduction in size of photographs, it has proved to be particularly
beneficial for many libraries that are today using it for documentation.
In microphotography, the photographer uses a
special negative known as a microfilm to preserve the images. Here, the subject
to be photographed (documents etc) may be photographed in one of two ways; a
linear array or a two dimensional array.
Microphotography - Linear Array
The ordinary microfilm roll is a good example of
linear array micrograph. The standard film measure 16mm, 35, 70mm or 105mm in
width and may be perforated on one
or either edges.
Whereas the 35mm perforated film can be used in 35mm cameras,
the unperforated one can only be used in special cameras that have no sprocket
wheels. The 35mm film is particularly preferred not only because it's
economical, but also because it has been shown to be easier to use.
Typically, the photographer photographs
consecutive pages of the document by capturing a single or a pair of pages (two
pages of open books). In this case, the microfilm frame will either take a
single page or two pages. This process allows the photographer to capture
images of an entire book in a microfilm roll, which can then be saved for
copying when needed.
Given that microfilm rolls tend to be of greater lengths,
microfilm strips which are composed of six frames can also be used. For reading
purposes, microfilm strips have been shown to be more suitable compared to
microfilm rolls. This is largely due to the fact that it's easier to find a
specific page in a strip that contains six frames. However, microfilm rolls are
more convenient when it comes to continuous copying compared to the strips.
Microphotography Two Dimensional Arrays
Two dimensional array micrographs tend to carry
more pages compared to the microfilm and the microfilm strip. This makes the
two dimensional array more convenient for library applications given that their
size allows for many more documents to be photographed and saved.
Microphotography is also known as microfilming.
Essentially, a microfilm is a photographic
record used in microphotography.
There are different types of microfilm
*Other than the roll film, documents are
sometimes copied onto a sheet known as a microfiche which can reduce a
document to about 0.25 percent of its normal size.
Silver Halide Film
Silver halide film is a type of film that uses silver halide a chemical compound that had been used in the photograph industry for the past 150 years. The film has been shown to be the most light sensitive films making ideal for recording greater variance of density and contrast present in the material of interest.
This property also provides an advantage in that it allows the film to record high level of detail and consequently provides rich tonal variance. When used in microphotography, silver halide film provides clear images of the highest resolution and thus high quality images when copied and reproduced. This also makes it the film of choice when longevity and quality are intended.
Types of Silver Halide films:
The vesicular film is commonly referred to as
vesicular because the images formed are composed of vesicles (small bubbles).
That is to say that the images formed on the film are made up of small
bubbles that are inside the body of the film itself.
When in use, heat causes
the vesicles to harden as the film is processed. One of the major strengths of vesicular films is that they are fairly resistant to stretching. However, they
can be damaged under high heat given that high heat causes the bubbles to
deform, which affects the quality of the image(s).
Some of the other
advantages of vesicular film include:
- The image can be reversed
(positive to negative)
- They can withstand daylight
- Dry thermal process can be
used for processing
- Cost less
With regards to the image, the quality of the
image produced using vesicular film is similar to that of Silver Halide film.
Because of its capacity to withstand tougher conditions compared to other
films, vesicular film has been shown to be ideal for high-use applications.
The Diazo films are a type of films that are
made up of light-sensitive diazonium. Compared to the other films, Diazo films
are inferior and thus used for dispensable material. For this film, the
mechanism involves using ammonia fumes for the chemical processing of exposed
diazonium salts which in turn produces Azo dyes.
The issue with the film is
that this dye has the tendency to fade off, which results in the loss of the
image. While they tend to be less costly compared to the other types of films,
the other two (Vesicular Film and Silver Halide Film) are recommended given
that they produce clear, high quality images that can last longer.
Cameras and Equipment
Essentially, A microform is a micrographic
reproduction on a film. To create microforms, special cameras and equipment are
required. Planetary and rotary cameras are some of the cameras used to capture
This is a manually operated camera that is positioned
above the document (stationary) to capture images. With a planetary camera, one
of the biggest advantages is that it's possible to film various types of
permanently bound documents including books and large-sized documents without
causing damage The camera is also capable of higher resolution which makes it
ideal for documents that are finely-detailed.
Also referred to as the flow camera, the rotary
camera is an automatic camera. For this camera, the film and documents move
synchronously in opposite directions as the images are captured.
captured at a faster rate compared to the planetary camera (30,000 images an
hour). In addition, a majority of rotary cameras place numbers and blips at the
edge of the film, which helps with numbering.
Some of the other equipment used includes:
- Overhead lamps
- Voltage control device and
voltage readout device
A microfilm reader (or reader printer) is used
to determine whether the microfilm is ready to be used for reading purposes by users.
Using a microfilm reader, it becomes possible to observe and evaluate the
crispiness of the images as well as the order in which they have been filmed.
This is an important process in quality control as it ensures that the
films are as they should be before being stored or released for use.
the features to consider when purchasing the reader or reader printer include:
- Exposure control
- The magnification of the
- Image rotation
- Connection to PC
- Ease of use
Apart from a microfilm reader, it's possible to
capture images of the film using a camera. This can easily be achieved by
removing the binocular eyepiece of a microscope and attaching a digital lens
reflex camera or attaching the camera onto the trinocular eyepiece.
recent advancements, there are many cameras that can be used for these purposes
including the Nikon D300 and D3, Olympus C2000/C2020/C3030/C4040Z digital
cameras or any suitable DSLR camera.
Benefits of Microphotography
- Durability - Durability is one of the
biggest advantages of microphotography. Given that microfilms (made of
polyester) tend to be stronger compared to the traditional film they can last
for a long time (about 500 years) keeping documents safe. In this case, the
documents are kept as permanent records.
- Saves space - Microphotography is a
process through which documents are significantly reduced in size so that they
can only be read when magnified. This therefore means that large volumes of
documents can be increasingly compressed not only saving them for long term
use, but also saving space (books/papers consume more space)
- Security - Books and other types of
documents cannot maintain their quality because of how they are handled (undergoing tear and
wear over time) however, microphotography keeps them safe and available for a
long period of time.
Limitations of Microphotography
Such microfilms as the vesicular film and Diazo
can be damaged through heat and humidity which can result in loss of data.
It can be time consuming to retrieve data with
open reel microfilm given that users have to go through the reel sequentially.
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Micrography - The Making of Microscopic Size
Photographs by N G Groom. Microscopy, 1986, 35 (6), pp.445-450. A modern
practical guide to making microphotographs on microscope slides.
Stevens, G. W. W., Microphotography: Photography
and Photo-Fabrication at
Extreme Resulation; 2nd ed.; John Wiley &
Sons, NY, 1968, pp 2-4.
LUTHER, F. Microjilm: a history 1839-1900.
Annapolis (Maryland), 1959.