Reading a bulb involves understanding the codes and numbers printed on it, which describe its shape, size, and other key characteristics. These markings allow you to identify the correct bulb for your fixture and desired lighting needs.
Here's a breakdown of how to interpret the information typically found on a bulb:
1. Understanding Bulb Shape Codes
The letter in the bulb's designation indicates its shape. Here are some common shapes:
- A: Arbitrary (standard household bulb shape)
- B: Bullet-shaped
- C: Cone-shaped
- G: Globe-shaped
- MR: Multifaceted Reflector
- PAR: Parabolic Aluminized Reflector
- R: Reflector
- T: Tubular
2. Deciphering Bulb Size Designations
The number following the shape code indicates the bulb's diameter at its widest point, measured in eighths of an inch.
- For example, an "A19" bulb signifies:
- "A" indicates the standard household shape (Arbitrary).
- "19" means the bulb's diameter is 19/8 inches, or 2 3/8 inches.
3. Base Type Identification
The base of the bulb also has a code, which indicates the type of socket it fits into. Common base types include:
- E26: Standard medium screw base (most common in North America)
- E12: Candelabra base
- E17: Intermediate base
- E11: Mini-candelabra base
- GU10/GU5.3: Twist and lock bases used for spotlights
4. Other Important Markings
Besides shape, size, and base, other markings on a bulb provide important information:
- Wattage (W): Indicates the power consumption of the bulb.
- Voltage (V): Specifies the voltage required for the bulb to operate correctly.
- Lumens (lm): Indicates the brightness of the bulb (the higher the lumens, the brighter the bulb).
- Color Temperature (K): Measures the color appearance of the light emitted by the bulb. Lower temperatures (2700K - 3000K) produce warm, yellowish light, while higher temperatures (4000K - 6500K) produce cool, bluish light.
- Color Rendering Index (CRI): Measures how accurately the bulb renders colors compared to natural light. A higher CRI (80 or above) indicates better color accuracy.
- Lifespan (hours): Estimated time the bulb will last before burning out.
Example:
Let's say you see a bulb marked "A19 E26 60W 800lm 2700K." This tells you:
- A19: Standard household shape, approximately 2 3/8 inches in diameter.
- E26: Standard medium screw base.
- 60W: Uses 60 watts of power.
- 800lm: Produces 800 lumens of brightness.
- 2700K: Emits a warm white light.
By understanding these codes and markings, you can confidently choose the right bulb for your specific needs and fixtures.
