1. Lumen is the physical unit to describe the luminous flux, which is interpreted in physics as a candlelight (cd, candela, luminous intensity unit, equivalent to the luminous intensity of an ordinary candle) at a solid angle (on a unit sphere with a radius of 1 meter, the angle represented by the cone corresponding to a spherical cap of 1 square meter, which corresponds to the central angle of the middle section of the circle about 65 °) The total luminous flux generated on the.
 2. Considering that the solid angle of the whole sphere is 4 π, the total luminous flux emitted by one candle is 4 π (about 12.56) lumens.
 3. The total solid angle of a sphere of any size is 4 π, so the total luminous flux of the candlelight is fixed at 4 π, which does not change with distance. Therefore, "the total luminous flux emitted by a candlelight at a position about 0.28m around it is 1 lumen" is a false statement.
 The basic details of lumen value in this article have been explained, and I hope it will be helpful to everyone.