This question is not about how to make illuminance (in lux) a linear function of voltage! It's about linearly representing the human perception of brightness, which itself scales logarithmic to the unit lux and is not equal to lux.
TL;DR: How can you transform the resistance of a light dependent resistor (up to 2MΩ) to an analog signal, so that it reflects the logarithmic growth in resistance as a (more or less) linear output?
First of all: Although the relationship between Lux and LDR resistance is inversely proportional (see Figure 4 from datasheet), light intensity itself is perceived logarithmically.
- Night sky: ~0.1 lux (=1MΩ)
- Fullmoon: ~1 lux (=100kΩ)
- Dark indoors: ~80 lux (=10kΩ)
- Living room: ~600 lux (=2kΩ)
- Overcast sky: ~1.000 lux (=800Ω)
- Bright sunlight / clear sky: ~50.000 lux (=40Ω)
But so far the typical usage of an LDR in a voltage divider has served me well. I can measure quite a big range with a 10bit ADC. The only downside is that it has an "increased resolution" spot around resistances similar to the fixed RS value, while magnitudes further out are getting more and more inaccurate.
This kind of "focal length" property might even be useful in situations where you want to specialize in a certain lux range (e.g. window light dependent LED dimmer). But as an academic question, I would like to know how to turn this curved measurement into a more linear output.