Lenses

Videography Overview

• Presented by Dr. Khaled Gamal

Lenses

• Definition: A lens is the fundamental component of a camera.

• Function: Collects reflected light and focuses it on the digital sensor.

• Types:

  • Fixed lenses (e.g., in amateur pocket cameras)

  • Interchangeable lenses (e.g., in professional cameras)

• Key Variations:

  • Focal length

  • Maximum aperture

Focal Length

• Definition: Distance between the lens center and the focal point where light converges on the sensor.

• Importance: Must align exact distance for a focused photo.

• Measurement: Expressed in millimeters (mm).

Relationship Between Focal Length and Field of View

• Smaller Focal Length: Offers a wider angle of view.

• Larger Focal Length: Provides a narrower field of view.

• Examples of Focal Lengths:

  • 18mm, 24mm, 35mm, 55mm, 85mm,

  • 105mm, 135mm, 200mm, 300mm

Types of Lenses Based on Focal Length

• Categories:

  1. Prime Lenses

  2. Zoom Lenses

• Specific Examples:

  • Zoom Lens: EF 24-70mm

  • Prime Lens examples: 24mm, 50mm, 85mm

Prime Lenses

• Characteristics: Fixed focal length; shows one specific field of view.

• Advantages:

  • Faster with wider apertures (f/1.4, f/2.8)

  • Lightweight and sharper image quality

  • Cost-effective and portable

  • Suitable for low light and 'Bokeh' effect

• Disadvantages:

  • Less flexibility (requires movement for different angles)

  • Increased dust exposure on sensor with lens changes

Zoom Lenses

• Definition: Variable focal length enabling multiple angles of view.

• Standard Zoom Range: Typically 24-105mm or 24-70mm.

• Advantages:

  • Flexibility saves time and effort

  • Variety of framing options available

• Disadvantages:

  • Usually have narrower apertures

  • Less ideal for portrait photography

  • More expensive and heavier

  • Lower image sharpness, especially in superzoom lenses

Maximum Aperture

• Definition: Indicates the widest opening a lens aperture can achieve, noted on the lens barrel.

• Importance:

  • Wider maximum apertures facilitate better performance in low light and enhance control of depth of field (DoF).

• Descriptor:

  • A lens can be classified as "faster" or "slower" based on its f-number (e.g., f/3.5 is faster than f/5.6).

Variable Maximum Aperture in Zoom Lenses

• Example: 18-55mm f/3.5-5.6 zoom lens.

  • Aperture at 18mm: f/3.5

  • Aperture at 55mm: f/5.6

Types of Lenses Based on Focal Ranges

1. Wide-angle Lenses

2. Normal Lenses

3. Telephoto Lenses

• Optical Characteristics: Different categories serve specific photography needs.

Wide-angle Lenses

• Focal Length: Usually below 35mm.

• Characteristics:

  • Wider field of vision for landscapes, architecture.

  • Great depth of field (sharp images throughout).

  • Distortion of images (especially at edges).

• Sub-categories:

  1. Ultra Wide-Angle Lenses: Below 24mm

  2. Fish-eye Lenses: Curved, exaggerated images, usually below 14mm.

Normal (Standard) Lenses

• Focal Length: Typically between 35mm and 70mm; normal prime lens is usually 50mm.

• Characteristics:

  • Mimics human vision, versatile for different photography types.

  • Offers large maximum apertures for shallow DoF.

  • Minimal perspective distortion.

Telephoto Lenses

• Focal Length: Usually from 85mm up to 300mm for standard telephotos.

• Characteristics:

  • Narrower angle of vision, ideal for distant subjects.

  • Provides shallow depth of field for portraits.

  • Common in sports and wildlife photography.

• Super-Telephoto Lenses: Over 300mm, used for very distant subjects like the moon.

Macro Lenses

• Function: Specializes in close-up photography of small subjects (e.g., flowers, insects, and jewelry).