BPB and TRITC filter spectra

Two data sets:

BPB absorbance — Nanodrop UV-Vis spectrum of bromophenol blue dye at the concentration used for the stepped-height channel measurements (0.1 mm path length).
TRITC filter transmission — raw transmitted intensity through the TRITC bandpass filter measured by an Ocean Optics spectrometer.

BPB absorbance spectrum (Nanodrop, 0.1 mm path)

TRITC filter transmission spectrum

Overlay — BPB absorbance and TRITC passband

Effective ϵc through the TRITC filter

The camera integrates light across the TRITC passband, not at a single wavelength. The effective transmittance is the filter-weighted average of the BPB transmittance:

$$T_\text{eff} = \frac{\int S(\lambda)\,10^{-A(\lambda)}\,d\lambda}{\int S(\lambda)\,d\lambda}$$

where $S(\lambda)$ is the TRITC transmitted intensity and $A(\lambda)$ is the BPB absorbance at the Nanodrop path length $l_\text{ref} = 0.1\,\text{mm}$. Applying Beer–Lambert gives the effective $(\varepsilon c)$ product:

$$A_\text{eff} = -\log_{10}(T_\text{eff}) = (\varepsilon c)_\text{eff}\,l_\text{ref} \quad\Rightarrow\quad (\varepsilon c)_\text{eff} = \frac{A_\text{eff}}{l_\text{ref}}$$

This value applies directly to the stepped-height channel measurements because the camera sees the same filter-weighted signal.

Quantity	Value
Wavelength overlap	220–748 nm
T_eff	0.26916
A_eff (at l = 0.1 mm)	0.56999 AU
(ϵc)_eff	5.6999 AU/mm