Pixel

What is a Pixel?

A pixel (short for "picture element") is the smallest addressable element in a digital display. It's the fundamental building block of all digital images and screens. Each pixel can display different colors by varying the intensity of its three subpixels: red, green, and blue (RGB).

Pixel Structure

Subpixels

Every pixel consists of three subpixels:

• Red subpixel - Controls red color intensity
• Green subpixel - Controls green color intensity
• Blue subpixel - Controls blue color intensity

By combining these three primary colors at different intensities, a pixel can display millions of colors.

Color Creation

• White: All three subpixels at maximum brightness
• Black: All three subpixels turned off
• Red: Only red subpixel on
• Yellow: Red + Green subpixels on
• Cyan: Green + Blue subpixels on
• Magenta: Red + Blue subpixels on

Pixel Counts by Resolution

Pixel Density (PPI)

PPI (Pixels Per Inch) measures how many pixels fit in one inch of screen space.

Common PPI Values

• 72-90 PPI: Older desktop monitors
• 96-110 PPI: Standard desktop monitors
• 110-140 PPI: Modern desktop monitors
• 140-220 PPI: Laptops and high-end monitors
• 220-400+ PPI: Smartphones and tablets (Retina displays)

Calculating PPI

PPI = √(width² + height²) / diagonal screen size in inches

For a 27" 4K monitor:

PPI = √(3840² + 2160²) / 27 = 163 PPI

Pixel Pitch

Pixel pitch is the distance from the center of one pixel to the center of the adjacent pixel, measured in millimeters.

• Smaller pitch = Higher pixel density = Sharper image
• Larger pitch = Lower pixel density = Visible pixels

How Pixels Work

LCD Pixels

1. Backlight shines through the pixel
2. Liquid crystals twist to control light passage
3. Color filters create RGB subpixels
4. Varying intensity creates different colors

OLED Pixels

1. Organic compounds emit light directly
2. No backlight needed
3. Each subpixel lights up independently
4. True blacks when pixels are off

Pixel Defects

Dead Pixel

• Permanently black
• Transistor completely failed
• Cannot be fixed
• Most visible on light backgrounds

Stuck Pixel

• Permanently showing one color
• Subpixel stuck on or off
• Sometimes fixable
• Most visible on dark backgrounds

Hot Pixel

• Permanently white (all subpixels stuck on)
• Type of stuck pixel
• Very noticeable on dark content

Pixel Response Time

Response time measures how quickly a pixel can change from one color to another, typically measured in milliseconds (ms).

• 1-2ms: Excellent for gaming (TN panels)
• 4-5ms: Good for gaming (IPS panels)
• 8-10ms: Acceptable for general use
• 16ms+: May show ghosting in fast motion

Types of Response Time

• GtG (Gray to Gray): Most common measurement
• BtW (Black to White): Less commonly used
• MPRT (Moving Picture Response Time): Perceived motion clarity

Pixel Refresh Rate

Refresh rate is how many times per second the display updates all pixels, measured in Hertz (Hz).

• 60Hz: Standard for most displays
• 75Hz: Entry-level gaming
• 120-144Hz: Popular for gaming
• 240Hz: High-end gaming
• 360Hz+: Professional esports

Pixel Aspect Ratio

Common pixel aspect ratios:

• 1:1: Square pixels (most modern displays)
• Non-square: Some older or specialized displays

Testing Pixels

To test for pixel defects:

1. Use solid colors - Display black, white, red, green, blue
2. Check all areas - Scan the entire screen systematically
3. Dark environment - Better visibility of defects
4. Use tools - Dead pixel test tools provide comprehensive testing

Pixel Technologies

Traditional RGB

• Standard arrangement
• Equal-sized subpixels
• Most common layout

PenTile (OLED)

• RGBG arrangement (two green subpixels)
• Smaller effective resolution
• Used in many OLED displays
• Better longevity for blue pixels

Quantum Dot

• Enhanced color accuracy
• Wider color gamut
• Used with LED backlighting