Signal-to-noise ratio (SNR)
How clean a night vision tube's picture is in very low light. Higher means less sparkle and grain on dark nights.
What it means
Every night vision picture contains some noise: a shifting sparkle or grain, sometimes called scintillation, that comes from the tube itself. Signal-to-noise ratio (SNR) compares the useful picture to that noise, measured at a set, very low light level. Current tubes commonly list figures from about 20 to 30 or a little above. Higher is better.
What it changes in the field
SNR matters most when light is scarce: a moonless night, deep shadow under trees, or a field with overcast skies. A high-SNR tube shows a calmer picture and lets you pick out a dark hog against dark brush. A low-SNR tube shows more sparkle, and fine detail drowns in it. Under a bright moon the difference shrinks.
Many experienced users weigh SNR above resolution for hunting, since most hunting happens in the low light where SNR does the work.
What to look for
- The SNR itself, not just the FOM. Two tubes with the same FOM can differ in SNR, and the higher-SNR one usually performs better on the darkest nights.
- Whether the figure is a minimum, typical value or range.
- Filmless and thin-filmed tubes, which are often designed for higher SNR.
Many tube sellers publish no SNR at all. When it is missing, a per-tube data sheet is the way to find it.
How we use it on this site
We record SNR as the maker publishes it, with its basis, or leave it blank.