Focus Problem with SmartPhones or HandHeld Digital Cameras
Even under the best of conditions, it can be difficult to produce good quality document scans from a handheld digital camera or smartphone.
You need to balance a combination of zoom, f-stop, aperture settings, shutter speed and camera positioning to get an acceptable image.
It generally takes quite a bit of trial and error, and of course under the less than ideal conditions it becomes even more difficult to get a good quality scan.
In addition, at low shutter speeds, even the tiniest imperceptible shaking of the camera will create a blurry out of focus image. In addition, many lower end smartphones and digital cameras do not offer a good depth of field at the close distances necessary for document scanning. As a result, the document will appear blurry around the edges.
The image segment below is from a handheld 8 MP Smartphone with a shutter speed of 1/100 sec.
The image segment below is from the TopOCR Personal Reading Assistant, notice the improved sharpness that produces a vast improvement in OCR performance!