Stated range, real range: reading the figures
How many ranges are there?
Three, and confusing them falsifies any comparison: range by eye, which depends on the light; range with a detector, electronic and much longer; and the range of the remote control, which says nothing about the line. Comparing two instruments means comparing the same one of the three.
| Type | What it measures | Order of magnitude |
|---|---|---|
| By eye | Distance at which the line stays visible | A few to a few tens of metres |
| With a detector | Distance at which the beam is detectable | Two to three times further |
| Of the remote control | Operating distance, unrelated to the beam | Variable |
On our 16-line, the manufacturer states 20 m by eye and up to 50 m with the detector. It gives no range for the remote control: that is exactly the kind of figure we do not invent.
Why is the real range shorter?
Four factors, in order of weight: the ambient light, far and away the first, since a line visible at 20 m in a corridor disappears at 3 m on a sunlit terrace; the surface aimed at; the angle of incidence, which spreads the line; and the state of the optics, which scatters the beam.
- Ambient light. By far the first. The same line visible at 20 m in a corridor disappears at 3 m on a sunlit terrace.
- The surface you aim at. White matt plaster sends back a great deal; bare concrete, dark tiling or glass send back little.
- The angle of incidence. A line arriving at a steep angle on a wall stretches out and loses intensity per unit length.
- The state of the optics. A dusty or scratched exit window scatters the beam and cuts the contrast.
What does “up to” mean?
That the value is a maximum obtained in favourable conditions, not a guarantee. That is why our pages write “up to 30 m” explicitly rather than “30 m”: the qualifier is part of the figure, it does not fall away when the figure moves into a table.
The same logic applies to “about” on a run time, or to the “±” of a self-levelling range.
How do you compare two models honestly?
A model stated at 50 m with a detector and another at 30 m without one do not compare. That is the commonest mistake in any comparison. Check that the two figures are of the same kind, then compare accuracy, which depends neither on the light nor on the surface.
- Check that the two figures are of the same kind: two ranges with a detector, or two by eye.
- See whether the manufacturer states the conditions. “In typical conditions” is worth more than a bare number.
- Then compare the accuracy, which depends neither on the light nor on the surface, and is therefore far more comparable.
A model stated at 50 m with a detector and another at 30 m without one do not compare. That is the commonest mistake in any comparison.
Does accuracy vary with distance?
It scales in proportion to distance: an instrument stated at ±1.5 mm at 5 m drifts in theory by 1.2 mm at four metres, and by 6 mm at twenty. The 12-line and the 16-line therefore read on the same basis.
Unlike the range, that figure can be checked at home: the 180° reversal test takes five minutes.
What to take away before buying?
A stated range serves to place an instrument in a category, not to predict what will happen on your job. If you work outdoors, the only question that counts is the one about the detector. The full section is under laser levels.
See the 3D laser levels Distance meters read the same way: the 80 and 120 metres of both our distance meters are measured on a target plate, not on a pale wall in full sun.
- Three different ranges sit side by side on one product page.
- “Up to” marks a maximum in favourable conditions.
- Ambient light is the first thing that cuts the range.
- Accuracy compares better than range, and can be checked at home.