Barco K5960051-01 User Manual

Barco - RHDM-1701 - User manual    157

Video signal processing

5.4  Effective gamma

The Rec.709 encoding equation assumes a linear tail and a power function with an exponent 0.45.
However, because of the linear offset and scaling, it is not correct to state that the Rec.709
encoding equation is described by a gamma of 0.45. The Rec.709 encoding equation is best fitted
with a pure power function with an exponent 0.52 (see figure below). We call this “best fit” the
“effective gamma

”.

 Figure 55: The Rec.709 encoding equation fitted with a power function

⎪

⎪
⎩

⎪

⎪
⎨

⎧

≤

≤

<

≤

−

−

<

≤

−

−

−

−

−

=

33

.

1

018

.

0

018

.

0

004

.

0

004

.

0

25

.

0

099

.

0

099

.

1

5

.

4

4

099

.

0

)

4

(

099

.

1

'

45

.

0

45

.

0

1361