This can be expressed in terms of the experimental parameters, Edcmax

and K where


 Edcmax = (Ro2 + So max2) (6.7)


and K = Ro2/So max2.


Edc max is the maximum average exposure and K, frequently called the

beam balance ratio, is the ratio of the reference to signal beam

intensities. In terms of Es and Ebs these become


 Edcmax = 1/2 (Es + Ebf) (6.8)

and

 K = [(Es1/2 + Ebf1/2)/(Es1/2 Ebfl/2)]2


Under these conditions, the maximum amplitude of the diffracted signal

is given by 1/4(Ts Tbf). For all values of s(p) less than smax the

diffracted signal will be proportional to s(p), as desired.

 The Hurter-Driffield model, although the most common in

photographic work, is not directly applicable to holography.

Transmittance, the ratio of transmitted amplitude to incident

amplitude, is the fundamental parameter in holographic filters.

Plotting the transmittance vs. exposure is more convenient than

inferring the information from the D-log(E) curve. The model as

expressed in equation 6.4 assumes the response is piece-wise linear

with two breakpoints. This neglects the smooth non-linearity which

exists throughout the film response. Although easier to analyze, the

piece-wise linear model does not predict the non-linear effects in the

regions near the breakpoints. To predict more accurately this non-