On 25 Feb 2007 19:01:05 -0800, "Weatherlawyer"
wrote:

They have a self levelling one for £37 49 and a Rotary one for
the same price. Yet the bumph says that they are both self levelling.

There are two sorts: line generators and flying spot rotaries.

Line generators have a lens system that projects a line. Usually it has
two of them, at right angles. Rotaries have a single whirling mirror
that projects a single spot quickly enough to look constant. For much
more money you can also find twin spot rotaries.

They're both self levelling, owing to a pendulum. Usually line
generators are much more accomodating of tilt.

Both have an apparent brightness that varies with the angle of the
surface they shine on, so the "centre" of the projected line is usually
brightest and it tails off to the sides. The line generators are also
significantly brighter in the centre of the line, so their side
performance is relatively poor. Spot brightness is effectively
independent of range, until its diameter gets bigger -- it's the side
slant direction that limits their use, not the straight-on spot.

So for indoor use, such as tiling, get a line generator. They're cheap
and wonderful

For other uses, you ought to get a rotary, but you can't afford it
(still £200+). Cheapie rotaries are neither one thing nor the other.


The tripods are all far too short and basically worthless. You need an
adapter (cheap from a camera shop) to use them on a photographic
tripod.