Quick answer: Resolution in night vision is measured in line pairs per millimeter (lp/mm) - how many distinct black-and-white line pairs a tube can still tell apart across one millimeter of its image. Higher is sharper, and 64+ lp/mm is strong Gen 2+ territory. But resolution is only half the story: signal-to-noise ratio (the low-light "snow") is the other half, and figure of merit (FOM = resolution x signal-to-noise) is the honest single number that captures both.
What does lp/mm actually mean?
A line pair is exactly what it sounds like: one black line next to one white line. Resolution asks how many of those pairs a tube can squeeze into a single millimeter of its image before they blur into gray. If a tube resolves 64 line pairs per millimeter, it can still show 64 distinct black-and-white transitions in that millimeter; push finer than that and the pattern smears together. So lp/mm is a direct measure of how much fine detail the tube preserves. It is the same idea as pixels on a screen or dots on a print, just expressed as pairs of lines per millimeter because that is how the test targets are drawn.
How is resolution measured on a real tube?
On a test station, not by eye. The tube is placed in front of a standardized chart - the USAF-1951 bar target is the classic one - printed with groups of parallel lines that get progressively finer. A technician records the finest group the tube can still resolve, and that group corresponds to a specific lp/mm figure. The industry workhorse for this is the Hoffman ANV-126 class of test station, the same equipment behind the numbers on a proper QC sheet. Because tubes off the same production line genuinely vary, this per-unit measurement is the only way to know what your specific serial number does, which is the whole argument for shipping the sheet with the tube.
The line-by-line walkthrough of everything else on that document, from the blemish map to the serial linkage, is in how to read a QC sheet.
What lp/mm numbers are actually good?
For a Gen 2+ tube, 64 lp/mm and up is genuinely strong, and the best examples climb higher. Lower figures are not automatically bad, but they mark a tube that will look softer on fine detail like distant branches, wire, or lettering. The trap is treating resolution as the whole scorecard. A tube can post a high lp/mm number and still disappoint on a dark night if it is noisy, because resolution is measured under controlled light while your real nights are not controlled at all. That is why the number to compare across listings is not raw lp/mm but figure of merit, which folds resolution together with the noise figure into one honest value - the reasoning behind pricing on measured numbers rather than generation labels is in Gen 2+ vs Gen 3.
Why is resolution only half the picture?
Because the other half is signal-to-noise ratio, and it is the half your eyes feel first. Signal-to-noise measures how much real scene the tube delivers versus how much random scintillation "snow" it adds when light gets scarce. A sharp but noisy tube resolves fine lines under bright test conditions yet turns grainy the moment you take it into a genuinely dark field, while a slightly softer tube with high signal-to-noise stays clean and usable. This is why the honest single number is figure of merit: FOM = resolution x signal-to-noise. Multiply the two and you get a value that punishes a tube for being weak in either dimension, which is exactly what you want from one number. When you compare tubes, compare FOM per dollar, and use the two factors underneath it to understand why a given FOM landed where it did. The three-question filter for getting those numbers out of a seller is in PVS-14 spec sheets compared.
Our pick: a PVS-14 with its measured resolution and signal-to-noise printed on the sheet in the box, so you buy the number, not the adjective - from $1,749.95. PVS-14 - from $1,749.95. Free G24 mount, 1-year warranty.
Frequently asked questions
What is a good lp/mm for a night vision tube?
For a Gen 2+ tube, 64 line pairs per millimeter and up is strong, and the best examples go higher. Lower figures look softer on fine detail. Just do not judge a tube on resolution alone, because a high lp/mm number can still hide a noisy image.
How is night vision resolution measured?
On a test station using a standardized bar chart, most often the USAF-1951 target on a Hoffman-class ANV-126 station. The tube views progressively finer line groups, and the finest group it can still separate sets its lp/mm figure. It is measured per unit because tubes genuinely vary.
Is higher resolution always better in night vision?
Sharper is better all else equal, but all else is rarely equal. A tube with high resolution and low signal-to-noise can look grainy on a dark night, while a slightly softer tube with clean signal-to-noise stays usable. That is why figure of merit, not raw resolution, is the number to compare.
What is the difference between resolution and FOM?
Resolution is one factor - fine detail in line pairs per millimeter. Figure of merit is resolution multiplied by signal-to-noise ratio, so it captures both sharpness and low-light cleanliness in a single value. FOM is the honest number to compare across tubes because it cannot be gamed by one strong figure.
Resolution tells you how sharp; signal-to-noise tells you how clean; figure of merit is the one number that respects both. Every Night Operators unit ships with the measured record of the tube in the box, a free G24 helmet mount, and a 1-year manufacturer warranty - 17,000+ orders since 2023, worldwide with duties pre-paid. The PVS-14 starts at $1,749.95.