First, I might suggest printing off the target :) The camera might not be reacting well to the backlighting on the monitor. Good lighting is always important in AR, but we're typically talking ambient lighting.
To find the resolution of the camera image, use the following code snippet anywhere you have the State object:
QCAR::State state = QCAR::Renderer::getInstance().begin();
QCAR::Frame frame = state.getFrame();
for (int i = 0; i < frame.getNumImages(); i++)
const QCAR::Image* image = frame.getImage(i);
int width = image->getWidth();
int height = image->getHeight();
LOG("rgb565 %dx%d", width, height);
LOG("rgb888 %dx%d", width, height);
LOG("grayscale %dx%d", width, height);
LOG("yuv %dx%d", width, height);
The rgb565 camera image is rendered to the background, and the grayscale image is used for tracking. I'm getting 400x240 for the grayscale image on my HTC desire.
I'm not sure if you're going to be able to add auto-focus functionality on your own, but I'm asking around. I'll let you know what I find.