1. Check the resistor. ResistorVision currently only works on 4-band beige axial resistors. Blue and 5-band resistors are not currently supported, nor are surface-mount resistors.
2. Check the background. ResistorVision needs a colorless background (preferably white or gray) to be able to detect a resistor. A white sheet of paper or index card works fine.
3. Check the image size. Move the iPhone until the resistor almost fills the rectangle in the center of the screen.
3. Check the focus. If the on-screen image of the resistor is blurry, ResistorVision will have trouble decoding it. Try to resetting the focus by moving the phone closer or further from the resistor. Or point the camera at a far-away object momentarily, then point it back to the resistor.
Send us a Screenshot
If you still can't get ResistorVision to read a resistor, please help us out by taking a screen shot of it. To do this, hold down the power and home buttons at the same time until the screen flashes. Then go into the Photos app, and email the screen shot to the address listed in the on-screen help. Please mention what model iPhone you are using, and what the lighting conditions were. Your screen shot will be added to our test data, and help make future versions of ResistorVision even better.