Low-Light Performance Calculator Compare light gain, perceived brightness, and overall low-light performance in relation to objective lens diameter, magnification, exit pupil diameter, light transmission, approximate exit pupil diffraction, and eye pupil diameter.      For Fixed & Variable Power Scopes  Your Eye Pupil Diameter at Night: mm     How to Measure?     Click for Quick Estimate  Number of Scopes to Compare: 1 Scope2 Scopes3 Scopes4 Scopes5 Scopes6 Scopes7 Scopes8 Scopes9 Scopes10 Scopes Enter only two of the three scope properties for each line below: Use only the first line for fixed-power scopes, or both lines for variable-power scopes  Scope #1   Optional Title:   Light Transmission: %      Fixed or Minimum Magnification:      Magnification: x   Objective Lens Diameter: mm   Exit Pupil Diameter: mm   Optional Maximum Magnification:      Magnification: x   Objective Lens Diameter: mm   Exit Pupil Diameter: mm  TIP: Resolution, contrast, and realistic light transmission greatly affect the low-light performance. Because these properties are not available for most scopes, this calculation is best used for comparing scopes among the same brand and scope line. If you are unsure of the utilized benchmarks for Light Transmission, it may be best to leave Light Transmission fields empty.  Perceived Brightness Calculation Method:  Stevens' Power Law  Weber-Fechner Law     How To Choose?

CORRECTION: Please enter two of the three scope properties for each line for Scope #1. Enter positive values only.