Aerial photography - Commercial

Aerial Photography
Steve Allen

Most photographers who are involved in commercial work will, sooner or later, be asked to undertake aerial photography. The type of work most often requested is photography of buildings, industrial sites, construction sites, etc. Aerial survey work & mapping, and air-to-air photography are the work of a specialist few and not usually for the general photographer.

If you are about to take on some aerial work for the fist time, it will help to know some of the problems and restrictions associated with aerial photography in advance.

The aircraft
My preferred option is a four-seater helicopter with the left side rear door removed. I will normally sit in the left rear seat, behind the pilot, so we both have the same field of view. I wear a safety harness to allow me to sit with my legs out of the door with my feet on the landing skids. This gives me an uninterrupted 180 degree field of vision.

Helicopters are very noisy at the best of times, even more so with the door off, so to have any chance of conversation with the pilot you will need to wear a 2-way radio headset.

The helicopter is my preferred option, being able to hover and give a stationary platform and maybe get into positions a fixed wing aircraft would find difficult. However, most of my aerial work is undertaken using a fixed wing aircraft, usually a Cessna 172. The reason for this is the relative cost. You can hire a fixed wing light aircraft and pilot from around £140 per hour, but a helicopter will cost from about £375 per hour. Add to these prices the landing fees and you can see that aerial photography is not cheap!

The Cessna 172 is a good aircraft for aerial work, being able to operate from small grass landing strips, being able to fly relatively slowly and having a high wing, giving good visibility. A pilot who is experienced in aerial photographic work is worth his/her weight in gold!

CAA Restrictions
The Civil Aviation Authority control all civil flights within The United Kingdom. It is only legal to undertake commercial aerial photography from an aircraft flown by a licenced commercial pilot.

A commercial pilot will have several million pounds worth of insurance to cover you, people and property on the ground, himself and the aircraft in the event of an accident. This is very important because your own life insurance will be void when undertaking aerial work.

Height restrictions play an important roll in aerial photography. All aircraft, fixed wing and helicopters have to maintain a minimum altitude of 1500ft if flying over built-up areas. Over the sea or open country aircraft can fly as low as 500ft. Helicopters can sometimes get special permission to fly lower, but this has to be requested and granted by the CAA.

If you are photographing a ship at sea or oil platform within UK airspace you can fly as low as 500ft above the sea but no closer than 500ft to the ship or platform. If you want to take shots from directly above such a subject then the minimum hight within the 500ft radius is again 1500ft.

There are also other restriction to keep in mind, such as the controlled airspace around airports, military establishments such as air bases and gunnery ranges, and other specified places like say Sellafield Nuclear Reprocessing plant.

The Weather
I undertake the majority of my aerial photography during the Spring and summer months, roughly from April to October.

Good visability is a prime requirement. Sunny days with little or no cloud and, most importantly, no haze, are best. Early morning or late afternoon are very often the best times for aerial work as the longer shadows often help to define the features on the ground.

Finding your subject
Often, not as easy as you may think! Imagine you are commissioned to photograph a small factory building and compound from the air. The factory is not in an area that you know well, it's in the middle of many similar units on a large industrial estate in a large city. Finding this from the air can be difficult.

A bit of forward planning, before take-off will help a great deal. Go over OS maps with the pilot, look for local landmarks that will be easy to spot from the air. Look for large roads like duel carriageways, or railway lines that will lead you into the area of your factory. When in the air, your pilot will be able to get you into the general area, then follow your road or rail line to a point close to your target, then look for other landmarks that will help you pin-point the factory.

Film and equipment
For general (non-specialist) aerial photography no special equipment or film is required. I simply use a Mamiya 645 for medium format (or sometimes my Mamiya RZ if a larger negative is required) or a Nikon F4S for 35mm.

On my Mamiya 645 I use a 55 - 110mm Zoom lens for most subjects and occasionaly, a 105-210mm Zoom lens for smaller subjects. Remember to use a 1A UV 'haze' filter on your lens, they really do help.
It is advisable to use a safety line to tether your camera to the aircraft, just in case you drop it. A camera falling from 1500ft can do an awful lot of damage to people and property!

On sunny days I use 160 ISO colour negative film or 100 ISO colour transparency. In overcast conditions I will generally only shoot on negative material, and I switch to 400 or even 800 ISO stock.

In aerial photography a fast shutter speed is much more important than a small aperture and I regard 1/400 second as the slowest speed I would want to use. The aircraft will be moving very fast, may be jostled about in turbulence, and you and your camera may be in the slipstream of the propeller or downdraft of a helicopter's rotor making a fast shutter speed essential.

Balloons
Because of height restrictions over built-up areas it may not be possible to get the viewpoint you want from a light aircraft or helicopter. The use of a 'tethered balloon' could be the solution.

This is a small, un-manned, helium filled balloon. A medium format camera with a video link are suspended under the balloon which is tethered to a cable that can be winched out to the required height. Heights from 50ft up to a maximum of around 500ft are possible. (Heights over 200ft require CAA approval). In the control van the camera can be adjusted using the video link to view the composition on a monitor prior to making the exposure by remote control. Several companies around the UK offer this facility.

A Recent Aerial Photography Commission
This photograph is one of a series of montages produced for The Highways Agency to show proposed changes to the A64 in North Yorkshire.

To make the montage individual overlapping photographs were taken flying along an imaginary line, at 1200ft (special CAA permission granted). On this, the Rillington Bypass section, some 32 overlapping photographs were taken. These were then scanned at 300 DPI and joined in the computer.

Each image had a file size of 36mb and the final high resolution montage file was 365mb. This would give a maximum print size (for display at the public meeting) of 8 ft wide without any loss of detail.

If the area of the montage had been photographed in one shot it would have required the photograph to have been taken from about 5000 ft. The extra haze from that height, together with the lower resolving power of a single frame of film, would have resulted in an unacceptable loss of ground detail.

To help in flying along an imaginary line accurately, I used a pilot with a great deal of experiance flying for photographers and one who also has a Satellite GPS (ground positioning system) fitted to his aircraft.

Fujicolor NPH 400 ISO colour negative film was used as the client also wanted a set of 10"x8" colour prints of the individual shots. The negatives were scanned using a Polaroid Sprintscan 45 and the images combined in an Apple PowerMac G4 running Adobe Photoshop 6.

The 8 ft wide print was produced by a professional lab as an "LED" photographic quality glossy print on Kodak paper from the CD I supplied.

A very interesting and profitable job! Aerial Photography is not for the faint hearted, you may need a strong stomach and a fear of heights is not recommended. You will also need a strong enough cashflow to cover what can be quite large bills from the aircraft hire. Having said all that aerial photography can be both interesting and exciting to do AND very profitable.

By Steve Allen FBIPP, FMPA, QEP, ARPS