Enter OD value or transmission (%) to convert between them and find the attenuation factor.
ND Filter Reference
What is Optical Density (OD)?
OD = log₁₀(I₀ / I), where I₀ is incident intensity and I is transmitted intensity. Higher OD = less light passes through.
Transmission Formula
T = 10−OD = I / I₀. For OD 1.0, T = 10% (1/10 of incident light passes).
Stacking ND Filters
OD values are additive: ODtotal = OD1 + OD2 + ... Transmission multiplies: Ttotal = T1 × T2 × ...
Laser Power Attenuation
Pout = Pin × 10−OD. Use ND filters to safely reduce laser power for PL, Raman, or Kerr microscopy.
Common ND Filter Reference Values
| OD | Transmission | Attenuation |
|---|---|---|
| ND 0.1 | 79.4% | 1.26× |
| ND 0.3 | 50.1% | 2× |
| ND 0.5 | 31.6% | 3.16× |
| ND 0.6 | 25.1% | 4× |
| ND 1.0 | 10% | 10× |
| ND 2.0 | 1% | 100× |
| ND 3.0 | 0.1% | 1,000× |
| ND 4.0 | 0.01% | 10,000× |
| ND 5.0 | 0.001% | 100,000× |
Frequently Asked Questions
Why does OD 3.0 transmit only 0.1%?
Because T = 10−3 = 0.001 = 0.1%. Each OD unit reduces transmission by a factor of 10.
Can I add OD values when stacking filters?
Yes. OD values are directly additive: ND1.0 + ND2.0 = ND3.0. This is the main advantage of the logarithmic OD scale.
What ND filter do I need to reduce 100 mW to 1 µW?
Need to attenuate by 10⁵ (100,000×). OD = log₁₀(10⁵) = 5.0. Use an ND 5.0 filter or combine, e.g., ND2 + ND3.
Enter OD values of individual filters to compute their combined effect.
ND Filter Reference
Stacking ND Filters
OD values are additive: ODtotal = OD1 + OD2 + ... Transmission multiplies: Ttotal = T1 × T2 × ...
Example
ND1.0 + ND2.0 = ND3.0
Transmission: 10% × 1% = 0.1%
Common ND Filter Reference Values
| OD | Transmission | Attenuation |
|---|---|---|
| ND 1.0 | 10% | 10× |
| ND 2.0 | 1% | 100× |
| ND 3.0 | 0.1% | 1,000× |
| ND 4.0 | 0.01% | 10,000× |
Enter input laser power and OD value to compute the output power.
ND Filter Reference
Laser Power Attenuation
Pout = Pin × 10−OD. Use ND filters to safely reduce laser power for PL, Raman, or Kerr microscopy.
Examples (Pin = 10 mW)
ND1.0 → 1 mW
ND2.0 → 0.1 mW (100 µW)
ND3.0 → 0.01 mW (10 µW)
Common ND Filter Reference Values
| OD | Transmission | Attenuation |
|---|---|---|
| ND 1.0 | 10% | 10× |
| ND 2.0 | 1% | 100× |
| ND 3.0 | 0.1% | 1,000× |
| ND 4.0 | 0.01% | 10,000× |
| ND 5.0 | 0.001% | 100,000× |