Linear light-sensing circuit required

Hi all.

I'm trying to make a circuit to sense the whiteness of a surface.
Like white = 5V, black = 0V, and linear between.

I bought an SFH2030 photodiode which gave about 20 mV difference measuring
the reflected light from a cheap red LED.

Googling the web for a good circuit, I found this one

http://www.megspace.com/science/stp/pmt/sfh2030f.html

which is a bit overkill, I don't need to measure starlight.

Corresponding with the author, he said he still wasn't getting the circuit
working satisfactorily.

Anyone got any good tips about working with photodiodes?
Like whether they are best run in current or voltage mode, good transistor
circuits, do they need particular op-amps (most circuits I see seem to
insist on high-impedance CMOS op-amps not popular ones like LM741/LF351 etc.

Cheers, K.


.

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