LED "capacitance" won't get lower

[flotulopex]

Hello,

I've been reading some threads about the LED's capacity feature and that they can be used as "sensors".

Now, I made a short program where I involve 3 LEDs to be discharged and measured in time like this:
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=1583&stc=1&d=117804885 4">

The shema is simple: one port connected to all Anodes (through a 330 ohms resistor) and three ports connected each to one Kathode. I use a 16F88 @ 20MHz.

I reduced the code as much as I could and here it is:

LOOP:
    for Counter = 1 to 3                                                 
        PORTB.0 = 0 : PORTB.0(counter) = 1 'reverse power to the LED to "charge" it
        TRISB.0(counter) = 1               'make the last HIGH port an Input and...
        while PORTB.0(counter) = 1         '...read it. As long as port is 1, increment "Discharge"
            discharge = discharge + 1
        wend
        discharge(counter) = discharge     'store Discharge's value for later comparision
        discharge = 0
    next
    gosub display
    TRISB = 0
    goto loop
end

I know I can reduce the overall process time by modifying the program but this is currently not the problem since I want to reduce the discharge time of each LED.

I thought I would be able to lower the LED's capacitance by reducing the voltage applied to it. So I put a 10K instead of the 330ohms one.

I even added a 10Mohms resistor in parallel with the LED to make a kind of load.

Result: no change(!?). The time values never change.

What am I doing wrong here? Should I use a 40MHz PIC instead?