Mastering Photography: Techniques and Film Development

Posted on Dec 18, 2024 in Physics

Depth of Field

Depth of field refers to the area in front of and behind the subject that appears sharp in a photograph. In other words, it is the zone of acceptable sharpness within a photo that will appear in focus. Several factors influence the depth of field:

  • Aperture: The aperture controls the amount of light reaching the film or sensor.
    • A more open aperture (smaller f-number) results in less depth of field.
    • A more closed aperture (larger f-number) results in more depth of field.
  • Focal Length:
    • A longer focal length results in less depth of field.
    • A shorter focal length results in more depth of field.
  • Camera-Subject Distance:
    • The depth of field reduces as the camera-subject distance decreases.

Depth of field is particularly pronounced in landscape photography and macrophotography, where it can sometimes be limited to just a few millimeters.

Scanning

Scanning, also known as panning, is a technique where you follow a moving subject with your camera. The camera movement is typically limited to horizontal rotation on its axis.

  • Camera-to-Subject Distance: The closer the subject, the faster the panning speed required. For example, a plane moving at 900 km/h can be easily frozen with a relatively slow shutter speed if it’s far away.
  • Speed and Direction of the Subject: If the subject’s motion is parallel to the film plane, the relative speed is greater than if it’s perpendicular.
  • Lens Choice: Telephoto lenses are often preferred for panning because their narrow field of view and shallow depth of field help isolate the subject.
  • Ambient Light and Film: When panning, prioritize shutter speed over aperture to minimize the depth of field.

Freezing Motion

To freeze motion, you need to use a fast enough shutter speed to capture the subject sharply, even if it’s moving quickly.

  • Shutter Speed: For example, 1/250s might be sufficient to photograph children playing, but faster speeds are needed for closer or faster-moving subjects.
  • Subject’s Path: When the subject is moving towards the camera, its apparent motion is less, and it can be frozen with slower shutter speeds.

Shutter Curtains

Shutter curtains are two elastic curtains that create a slit between them. The width of this slit determines the exposure time.

  • Advantages:
    • They are independent of the lens, being located in the camera body.
    • They can provide very short exposure times, up to 1/8000s.
  • Drawbacks:
    • The inertia of the curtains can lead to uneven film exposure, although this is usually minimal.
    • Fast-moving objects can appear distorted due to the movement of the curtains during exposure.

Film Development

Dilution

Diluting the developer offers several advantages:

  • Easier time management.
  • Reduced grain size.
  • Increased negative definition.
  • Decreased loss of film sensitivity.

Temperature

The temperature of the developer affects the development process:

  • The recommended temperature is 20°C, with 18°C being considered normal.
  • Higher temperatures increase film sensitivity, but also increase the base fog and grain size.

Agitation

Proper agitation during development is crucial:

  • It prevents the buildup of exhausted developer on the emulsion surface.
  • Simple up-and-down movement of the spiral is insufficient.
  • In small tanks, agitation is typically done by inverting the tank several times.
  • Lack of agitation leads to low density, low contrast, uneven development, and increased base fog.
  • Excessive agitation can have a similar effect to increasing development time.
  • Fixer requires less agitation than developer.

State of the Bath

Developer oxidation is caused by oxygen in the air. Regeneration involves using liquids with a formula similar to the main bath, but with adjusted component ratios to compensate for losses during development.

Film Characteristics

When light strikes the film, the photosensitive silver salts undergo a change, forming a faint latent image. The intensity of the light and the duration of the exposure determine the strength of this effect. A film that has been exposed to light is considered to be”expose”.

Format

The most common film format is 135 film, also known as 35mm film. It is 35mm wide and has perforations on both edges. It typically comes in rolls of 12, 24, or 36 exposures.

Type

Film can be for color or black and white negatives, or for slides, which are used for projection or printing.

Sensitivity

Film sensitivity, measured in ISO, indicates how reactive the film is to light:

  • Higher ISO values indicate greater sensitivity.
  • ISO 100 is considered medium sensitivity.
  • ISO 200 is twice as sensitive as ISO 100.
  • ISO 50 is less sensitive than ISO 100.