Its been almost 2 years I think the great video experimenter shield need an upgrade with improved on board image processing ,color overly and color output etc in other words full feature frame grabber/processor for arduino 🙂
And how would you propose accomplishing all of that on an ATmega328 microcontroller? The reason it can’t do more than it does is because there is only 2K of memory in the Arduino, and you can’t generate the composite video color burst with a 16MHz clock speed. There’s only so much you can do with an Arduino.
I think you could use an external pot connected to A2. If you make a voltage divider using another resistor, then the resistance of the pot will determine a smaller voltage range.
For example: connect the 5V source to 30K or 40K of resistance, then to the left lead of the pot. The middle lead of the pot goes to A2. The rightmost lead of the pot goes to GND. This way, the full range of the pot will provide 0V – 1V to A2 and this will allow finer adjustment.