1 The Director of Photography – an overview

122 Practical Cinematography
Figure 14.1 Mired values of
colour temperature from
2000 to 6900°K
Figure 14.2 Mired shift
values of Wratten lightbalancing
or LB filters
°K 0 �100 �200 �300 �400 �500 �600 �700 �800 �900
2000 500 476 455 435 417 400 385 370 357 345
3000 333 323 312 303 294 286 278 270 263 256
4000 250 244 238 233 227 222 217 213 208 204
5000 200 196 192 189 185 182 179 175 172 169
6000 167 164 161 159 156 154 152 149 147 145
Positive – towards yellow Negative – towards blue
Filter Mired Filter
shift factor
81 – �9
81A – �18
81B – �27
81C – �35
81D – �42
81EF – �52
85C – �99
85 – �112
85B – �131
1
⁄ 3
1
⁄ 3
1
⁄ 3
1
⁄ 3
2
⁄ 3
2
⁄ 3
1
⁄ 3
2
⁄ 3
2
⁄ 3
Each filter can therefore be categorized as having a particular
Mired shift value irrespective of the light source it is affecting.
The value of this Mired shift can be expressed as:
Mired shift value
Filter Mired Filter
shift factor
82 – �10
82A – �21
82B – �32
82C – �45
80D – �56
80C – �81 1
6 6
10
� �
T2
10
T1
where T1 represents the colour temperature of the original light
source and T2 represents the colour temperature of the light after
passing through the filter.
The Mired shift value can be either positive or negative. If filters
deal with changes in the blue or red part of the spectrum they are
called light-balancing filters (LB filters). Brown or reddish filters, shown
in the left-hand column of Figure 14.2, lower colour temperature but
the Mired value will, being a reciprocal function, be increased. Such
filters, therefore, have a positive value. Bluish filters, shown in the
right-hand column of Figure 14.2, have a negative value.
Filters that deal with green, or its complementary colour magenta,
are known as colour-compensating filters (CC filters). They work in
exactly the same way as light-balancing filters in that the value is
always added, allowing for its mathematical sign. Figure 14.3 shows
the shift and filter factors for CC filters.
1
⁄ 3
1
⁄ 3
2
⁄ 3
2
⁄ 3
1
⁄ 3
80B – �112 1 2
⁄ 3