CCD Sensors, Pixels, and Digital Image Fundamentals

Incident light produces a weak electrical signal in the camera's receiver. This signal is amplified and converted into digital data, represented as strings of binary digits, forming individual color squares called pixels.

CCD Sensor Types

Different camera formats utilize CCD sensors with varying numbers of light-sensitive cells:

1. 35mm Camera: Features fewer light-sensitive cells, resulting in a lower-resolution image.
2. Medium Format Camera (6x6): Contains more light-sensitive cells than 35mm cameras.
3. Large Format Camera (9x12): Features significantly more sensitive cells for higher resolution.

CCD Sensor Characteristics

A CCD sensor inherently captures only the intensity (brightness) of light from the scene, not the color itself.

Color Capture with Filters

To produce a color image, a color filter array (typically red, green, and blue - RGB) is placed over the CCD sensor. Each pixel then records the brightness of the light corresponding to its specific filter color, blocking other colors. For example, a blue filter allows only blue light to pass to the underlying pixel, a green filter allows green light, and a red filter allows red light.

Understanding Pixels

Pixel Definition

Pixel is short for 'picture element' and represents the smallest individual component of a digital image. A digital image is formed by a large grid of these pixels. Each pixel typically represents a specific color, often determined by combining values for red, green, and blue (RGB).

Image Resolution

Image resolution determines the density of pixels within a given area, influencing perceived size and detail. Higher resolution means more pixels packed into the same area (smaller effective pixel size), resulting in greater image sharpness and detail.

Resolution is often expressed in pixels per inch (PPI) for digital displays or dots per inch (DPI) for printing. The total number of pixels (pixel dimensions) is calculated by multiplying the image width by its height in pixels (e.g., 1920x1080).

Digital Storage Units

• Bit: The smallest unit of digital data (binary digit: 0 or 1).
• Byte: Typically consists of 8 bits (also known as an octet).
• Kilobyte (KB): 1024 Bytes.
• Megabyte (MB): 1024 Kilobytes (or sometimes 1,000,000 Bytes in storage contexts).
• Gigabyte (GB): 1024 Megabytes (or 1000 MB).
• Terabyte (TB): 1024 Gigabytes (or 1000 GB).
• Note: 1 inch equals 25.4 mm (relevant for PPI/DPI calculations).

Types of Digital Images

Vector Images

Vector images are composed of lines, curves, and shapes defined by mathematical equations (vectors). They require relatively little storage space and can be scaled infinitely without losing quality.

Bitmap Images

Bitmap images (also called raster images) consist of a grid of pixels, typically generated by scanners and digital cameras. They lose quality (become pixelated) when significantly enlarged.

Understanding Bit Depth

Bit depth measures the amount of color information available for each pixel in an image. A higher bit depth allows for more available colors per pixel, enabling more precise color representation and smoother gradients.

Since each bit can be either 0 or 1, the total number of possible colors is calculated using the formula: Number of Colors = 2ⁿ, where 'n' is the bit depth.