The photograph (above) illustrates 3 different types of cameras used by the ‘pigeon squad’.
History of Aerial Photography and the Resolution of Glass Plate Cameras
Prepared by Emeritus Professor John Fryer.
A Short History of Photography
The principles of a perspective projection were understood from the late 1400s and exploited by artists such as Leonardo da Vinci and Albrecht Duerer.
By the 1830s various people experimented to find a method for capturing images using chemical preparations, prototype cameras and lenses.
Niepce and Daguerre
From 1830, Joseph Niepce’s method worked, but it took 8 hours for a positive exposure. The most successful experimenter was Frenchman Jacques Daguerre in 1837 who developed the process known as the ‘daguerreotype’ image.
Wet Colloidal Process
By the late 1840s a wet colloidal process which captured an image onto a glass plate allowed scientists involved with photography to develop scientific processes known as photogrammetry.
Photogrammetry
Photogrammetry is a technique which allows measurements in the real world to be extracted from one or more images.
Literally, photogrammetry means ‘light drawn to measure’.
Frenchman Aime Laussedat became known as the ‘Father of Photogrammetry’ when in 1849 he climbed church steeples across Paris and took glass plate photographs. He measured distances on those images and combined them to produce a map.
The Birth of Aerial Photography
“Nadar” – The Father of Aerial Photography
An extremely colourful character in France from the 1850s was Gaspard Felix Tournachon, always referred to as ‘Nadar’.
Always a ‘showman’, the late 1850s studio-based portrait of ‘Nadar’ (above) illustrates how he went aloft over Paris to take the first aerial photographs, made by the use of a ‘mask’ which slid across the negative glass plate to expose 8 separate images.
He realised the enormous potential for aerial photography (and photogrammetry) and ascended 80 metres in a hot air balloon over Paris to take the first aerial photographs in 1858.
Military Potential
The military soon saw the potential. Reconnaissance photography from balloons (and kites) was used by the Americans in their Civil War (1862) and by the French in campaigns against Spain and Prussia by the 1870s.
The Use of Kites
Unbelievably, up until the development of the aeroplane, kites were used in aerial photography as the main technology to get a photographer airborne.
Lawrence Hargrave in Australia had experimented with man-lifting box-kites since 1885.
Captain Baden-Powell had invented and perfected his ‘Levitor’ kite in England by 1894 and it was taken to South Africa for use in the Boer War, but arrived there too late to be used.
The ‘Man-Lifter War Kite’
Samuel Francis Cody patented his ‘Man-lifter War Kite’ in 1901. This was an improved version of Hargrave’s design and was large enough to comfortably support a man. They were kept air-borne by being released from the decks of ships which steamed along at a steady rate. The photographer was raised up to 500 metres in the air to allow coastal defences to be photographed for later analysis.
The Invention of Roll Film
Roll film for cameras was developed by George Eastman in 1884. This saw the development of the Eastman Kodak company and the general public could join in the photography ‘craze’ after the early mass-produced Brownie box-cameras became available.
Note that although there were usually 8 photographs on the reel of film, in the early days from the 1890s, the entire camera had to be returned to a Kodak agency for it to be extracted from the camera, developed and printed and a new roll of film installed!
Use of Pigeons During World War 1
One of the more bizarre episodes in the history of aerial photography was that during World War I “squadrons” of homing pigeons, each equipped with a single shot camera on a time-fuse, were used to shoot photographs from the air.
The photograph (above) illustrates 3 different types of cameras used by the ‘pigeon squad’.
Needless-to-say, the enemy soon trained birds of prey to attack these intrepid, but defenceless, aerial photographers.
World War I saw the accelerated development of cameras, film, lenses and aeroplanes … a trend which hasn’t slowed down since … think spy-planes, geo-synchronous satellites, drones, video cameras, digital devices, etc. etc.
Aerial Photography in Australia
By 1930, there was an aerial survey company known as Adastra Aerial Surveys which ‘flew’ out of Mascot Aerodrome in Sydney. By the time it was sold up in the mid-1970s, there were several aerial photography companies throughout Australia, mostly responding to the demand of the ‘Mining Exploration Boom’. These companies took the photographs and made the subsequent measurements and maps for the planning of roads, railways, mining leases, etc.
Aerial Photography During World War 2
During World War II there was a fairly accurate set of aerial photographs taken of the whole of the Sydney region by Adastra as a contract worth 612 pounds ($1,224) for the Department of Main Roads.
About 15 years ago, this 1943 set of photography re-emerged due to the efforts of staff in the photogrammetric section of the Dept of Main Roads in Sydney.
This set of aerial photography was neatly catalogued, put onto a CD and given a ‘user friendly’ interface with search capabilities. Until recently the CD was available for purchase for $39.95 but now it appears to be part of the NSW SIXMAPS system and freely downloadable in a number of formats.
It is hugely useful for family history and other researchers wanting to locate housing and development in Sydney in 1943.
Shortly afterwards, a 1944 set of aerial photography was flown of Newcastle and the coastal strip. It was a topic of conversation at the HLH meeting on 12 October 2021.
A preview of this 1944 Newcastle imagery is on the new Heritage Air Photo Enhancement (HAPE) facility set up by NSW Spatial Services, at Historical Imagery (nsw.gov.au)
What is the Resolution of Old Glass Plate Photos?
A question from 11 October 2021 Hunter Living Histories meeting concerned the accuracy of old glass plate photographs.
People marvel at the fact that they seem to be able to be enlarged and enlarged and yet still appear to show clear detail. Why is this so?
A Simple Explanation
Let us try to offer a simple explanation by comparing a typical 10-inch by 8-inch glass plate image with a modern digital camera.
(I am taking some liberties here by trying to make this explanation as simple and as understandable as possible.)
The glass plate photograph probably had a relatively slow exposure time and this meant the size of the individual grains of silver (which make up the photograph) were probably of a size between 1 to 3 micrometres (that is, a single grain of black/white on the photograph was 0.001 to 0.003mm).
To get such a photograph digitised into a computer, it would typically be scanned into pixels (little squares of information) at a resolution of 10 micrometres.
In other words, one mm by one mm of the photograph would contain 100 by 100 pixels (=10,000 pixels).
A glass plate photograph of 10 by 8 inches equates to 250 by 200 mm, or 50,000 square mm in area.
If each square mm contains 10,000 pixels from the digitisation process of a scanner, the entire photograph would contain 500,000,000 pixels (or 500 Megapixels).
The Digital Camera
About 20 years ago a regular digital camera was ONE Megapixel. And now in 2021, cameras have from 10 to 20 Megapixels on their sensing array, as do phone cameras.
Put simply, the 150 year-old glass plate image may contain 50 times as much information. And, be capable of much greater enlargement than your modern digital camera.
I have simplified this discussion and understand that lens distortions, ease of use, weight and size of camera, compatibility with computer processes and other factors have seen the demise of glass-plate and later film photography.
BUT DON’T THROW AWAY YOUR OLD GLASS PLATES!!
Emeritus Professor John Fryer
October 2021
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