A digital camera is used to take photographs at a school sports event. (a) Describe how a digital camera captures an image. [3] (b) State two features of th...

(a) How a digital camera captures an image:

1. Light from the scene passes through the camera lens and is focused onto an image sensor (CCD or CMOS). [1]
2. The sensor is made up of millions of tiny light-sensitive elements (pixels), each of which detects the colour and intensity of light falling on it. [1]
3. The analogue data from the sensor is converted to digital data by an analogue-to-digital converter (ADC) and stored as a digital image file. [1]

The lens controls how light reaches the sensor, while the sensor performs the actual conversion of light into electrical signals. The ADC then digitises these signals so they can be processed and stored by the camera's processor.

(b) Two features affecting photograph quality:

1. Resolution (megapixels): A higher resolution means more pixels are used to capture the image, [1] producing sharper and more detailed photographs that can be printed at larger sizes without visible pixelation. [1]
2. Lens quality/aperture size: A larger aperture allows more light to reach the sensor, [1] producing brighter and clearer images, especially in low-light conditions such as an indoor sports hall. [1]

(c) One advantage of digital over film:

Photographs can be viewed immediately on the camera's screen, allowing the photographer to retake any poor shots straight away. [1] There is no cost per shot and no need to develop film.

(d) How photographs are stored:

The digital data is compressed and stored in a file format such as JPEG (lossy compression, smaller files) or RAW (uncompressed, larger but preserving maximum quality). [1] The files are saved to a removable storage medium such as an SD card or CompactFlash card inside the camera. [1] Each image file also stores metadata including the date, time, exposure settings and resolution. [1]

(e) Two factors when preparing images for the web:

1. File size/loading speed: Images should be compressed (e.g. using JPEG format) and reduced in resolution to ensure fast loading times on the website. Image dimensions should be resized to match the display area on the web page to avoid wasting bandwidth. [1] [1]
2. Image quality: The colour depth should remain at 24-bit for good visual quality on screen. The resolution should be at least 72 ppi for screen display, ensuring images appear sharp without being unnecessarily large. [1] [1]

(f) Comparing a digital camera with a smartphone camera:

Advantages of a smartphone:

• A smartphone is lightweight and portable, and the photographer is more likely to have it readily available at the event. [1]
• Photographs can be shared instantly via email, messaging apps or social media without needing to transfer files to a computer first. [1]

Disadvantages of a smartphone:

• A smartphone camera typically has a smaller sensor and lens than a dedicated digital camera, producing lower quality images especially in low light or at distance. [1]
• A smartphone may have limited storage capacity compared to a camera with interchangeable memory cards. [1]

(g) Why low-light images appear noisy or grainy:

The camera sensor must amplify the weak signal from each pixel to compensate for the low level of light, and this amplification also amplifies random electronic noise, making the image appear grainy. [1]