1. Lighting calculations

3. =Luminous Flux / area of the sphere surface
The Illuminance: (E) شدة الإضاءة
=Luminous Flux / area of the sphere surface
E=Φ/A
E= I/ r2
= lumen/ m2 = lux

4. The luminance (Luminous Intensity) (I)شدة الاستضاءة I= Φ/ω cd Where: ω = solid angle = (Φ/A)* r2 = E* r2 Candela

5. Inverse square law Inverse square law: Double the Radius:
Surface area bounded by a solid angle of 1 sr now increases to 4m2
Luminous flux remains Φ = 1lm
Illuminance E drops from 1 lux to ¼ lux

6. What can we do with this? It’s the basic building lighting
We can find the illuminance on a desk from a incandescent light bulb overhead:
Bulb: 60W * 20 lm/W = 1200 lm
1200/4π ≈ 100 cd if point source
Desk : E = 100/22 = 25 lux
LUMINOUS EFFICACY
Is the ratio of the luminous flux emitted by a lamp to the power taken by it. (unit: LUMENS PER WATT, lm/W)

7. Calculation of point illuminance level: Ep
Which are generated by individual light source:
E = I/r2
But, r = h/ cos (∞)
So,
Where,
Luminous Intensity(I)
Hieght (h)
Light Incidence Angle (∞)
E p = I /h2 cos3 ∞

8. Factors affected on illuminance calculations
Room Reflectance
The room is considered to consist of three main surfaces:
(a) the ceiling cavity,
(b) the walls, and
(c) the floor cavity (or the horizontal working plane).
The effective reflectances of the above three surfaces affect the quantity of reflected light received by the working plane.

9. Factors affected on illuminance calcuations
Luminaire maintenance factor (LMF) is the proportion of the initial light output from a luminaire after a set time to the initial light output from a lamp after a set time.
Three factors must be considered in its determination:
(a) the type of luminaire,
(b) atmospheric conditions, and
(c) maintenance interval.
Room surface maintenance factor (RSMF) is the proportion of the illuminance provided by a lighting installation in a room after a set time compared with that occurred when the room was clean.
Utilization factor (UF) is the proportion of the luminous flux emitted by the lamps which reaches the working plane. Factors that affect the value of UF are as follows:
(a) light output ratio of luminaire
(b) flux distribution of luminaire
(c) room proportions
(d) room reflectance
(e) spacing/mounting height ratio

10. Lumen Method Calculations

11. i.e. initial bare lamp luminous flux
Where:
E = average illuminance over the horizontal working plane
    n = number of lamps in each luminaire
    N = number of luminaire
    F = lighting design lumens per lamp,
i.e. initial bare lamp luminous flux
     UF = utilisation factor for the horizontal working plane
     LLF = light loss factor
     A = area of the horizontal working plane

12. The Luminous Flux (Φ)= EA/MU

13. The Luminous Flux (Φ)= EA
Calculate the utilization factor
Calculate the Room Factor:
K = 0.8W + 0.2L he
Where: W= width of the room
L = length of the room
From the table find “η”
The Luminous Flux (Φ)= EA η

14. Room Factor It depends on room dimension
is the proportion of the initial light output from a luminaire after a set time to the initial light output from a lamp after a set time.
It depends on room dimension