focal length & angle of view

'The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more strongly, bringing them to a focus in a shorter distance.'-Wikipedia.

Contrary to common belief, focal length isn’t a measure of how long or short a lens is physically, but the distance in millimetres from the optical centre of a lens to the imaging sensor when the lens is focused at infinity.

Rather than being fazed by the physics, it’s easier to think of the way in which focal length affects image size.

For a camera with a full-frame sensor, for example, a standard lens (one that gives a similar perspective to the human eye) is 50mm.

Lenses with focal lengths less than 50mm are referred to as wide-angles – simply because they have a wider angle of view. Lenses with focal lengths greater than 50mm are known as telephotos, and these offer greater magnification thanks to their much narrower angle of view.

Angle of view? What’s that?


Essentially, the angle of view is the amount of a scene that a lens can take in, measured in degrees. For instance, a fisheye lens may offer an extremely wide 180° angle of view, meaning that it can capture everything in front of it (and to each side).
A 200mm lens, on the other hand, will offer a much narrower angle of view of 12.3°. This allows you to fill the frame with a considerably smaller amount of the scene that you’re trying to photograph.

lens based image making.

  I had to adapt alot of camera features whilst taking my series of photos for the 'Psychogeography' project. Apature settings, ISO, shutter speed and general settings.
  Because my area to shoot was a tunnel, depending on whether i was inside it or out, all the camera features would need to change and be ajusted to the dark or light situation. I also used the DSLR flash system when inside the tunnel as it was needed due to lack of sunlight inside.

Q and A on negative cleaning?

What is a proper way to clean a 35mm negative film stripe before scanning?

What chemicals can remove fingerprints, dust that does not come off by blowing, or strains of glue? What type of cloth does minimal damage when rubbing off dirt?

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For fingerprints and light dust you can use a microfibre cloth. If you have stubborn dirt, dust (or glue!) then you may scratch the emulsion if you rub with a cloth.

In that case you could try film emulsion cleaners, but I would just soak them in lukewarm water, perhaps with a single drop of dishwashing detergent to prevent streaking, then use a soft squeegee and hang to dry.

Dark Room health and saftey

Darkroom General Safety Rules:

• Limit access to the darkroom. Only approved persons should be allowed to work in the room.
• Practice good housekeeping. Keep the work area clean and uncluttered to prevent tripping over hazardous chemical bottles.
• Separate the wet and dry areas.
• Always segregate chemicals. (Don’t store acids near reducer).
• Use the least toxic chemicals available. Avoid cyanides, heavy metals and developers containing pyrocatechol or pyrogallol when possible.
• Do not store chemicals on the floor.
• Do not eat, drink or smoke in the darkroom.
• The darkroom should be well ventilated.
• Wear appropriate protective equipment whenever possible, such as gloves, goggles, etc.)
• Always wash hands with soap and warm water after working with chemicals.
• Know how to use emergency equipment prior to an actual emergency.
• Always Add Acid to water, never water to acid. (Remember ‘AAA’)
• Keep a spill kit in the darkroom.
• Do not use paper towels or saw dust to clean up acid spills as this may cause a fire.
• Pregnant women should not be exposed to powdered developer.
• Store all chemicals in locations that will minimize the chance of breakage and splashing.
• Label all containers.
• Keep all containers and trays closed or covered when not in use to prevent the release of toxic gases.
• Do not wash any chemicals down the sink (exceptions noted below).
  • All spent chemicals should be placed into an appropriate waste container. (A container the same as the one the chemical was originally shipped in is best).