Formulae!

Question 1

Formulae for calculating necessary illumination

Answer 1

fc = 25xf^2/t x EI

Lux = 269 x f^2/t x EI

For calculating T stop
(Square root)(fc x t x EI)/25
(Square root)(lux x t x EI)/269

Question 2

Calculating depth of field

Answer 2

H = F^2/f x CoC

ND= H x S/H + (S-F)

FD= H x S/H - (S-F)

Question 3

Storage per frame in bytes

Storage per second

Effect of compression

Answer 3

Per frame = resolution x 3 x bit depth/8
(NB 3 colours, and 8 bits in 1 byte)

Per second = storage per frame x frame rate
- multiply by 60 for minutes, 60 again for hours etc.

Effect of compression = uncompressed storage/compression ratio
(NB if compression ratio is 27:1, divide by 27)

Question 4

Inverse square rule for calculating falloff light

Answer 4

fc = cd/ft^2

lux = cd/m^2

Level of incident illumination is inversely proportional to the square of the distance from the source

ft = (square root)cd/fc
m =(square root)cd/lux

Question 5

Calculating MIRED shift

Answer 5

MIRED SHIFT = 1,000,000/target temp - 1,000,000/current temp

Question 6

Calculating transmission of light with gels

Answer 6

Required illumination = target illumination/gel transmission

Question 7

Calculating voltage drop

Answer 7

VD = 2 x R x I x L/Cmil

Question 8

Balancing the load

Answer 8

Total load = Total wattage of all fixtures/voltage of supply

Question 9

Power equations

Answer 9

Power = amperage x voltage

P = I x E

I = P/E

E = P/I

Amperage = voltage/resistance

I = E/R

E = I x R

R = E/I