Image Resolution W4 Flashcards
(12 cards)
What is the commonly accepted value for human visual acuity in radians?
3 × 10⁻⁴ radians (or 1/60th of a degree).
What is the formula for a small angle in radians?
θ ≈ H / D (where H is separation and D is distance to the eye).
At a viewing distance of 25 cm, what is the maximum pixel size for a smooth image?
0.0075 cm (75 microns).
For an 18 cm x 26 cm photo, how many pixels are needed to appear smooth?
Approximately 8.32 million pixels.
How many bytes are needed for that image using 24-bit color?
About 25 million bytes.
What is the required resolution in dpi (dots per inch) for the above image?
340 dpi.
What resolution does an XGA projector use?
1024 × 768 pixels.
What frame rate is typically required for smooth video?
20–25 frames per second.
How many bytes are needed to store a 2-hour movie at XGA resolution and 25 fps (uncompressed)?
Approximately 425 billion bytes.
Why is compression necessary for images and videos?
Because uncompressed data sizes are huge and inefficient to store or transmit.
How can a simple image like a 250 × 400 solid color image be efficiently stored?
By saving the dimensions and one color value (e.g., 65280), instead of storing each pixel.
What’s the big takeaway about image resolution and data size?
Higher resolution = more detail but much larger file size, so compression is essential.
