Taking photos of documents

Scanning isn't the only way to acquire images of your documents. You can photograph documents with a camera or a mobile phone and then open the photographs in ABBYY FineReader 14 and recognize them.

When taking pictures of documents, a number of factors should be kept in mind to make the photo better suited for OCR. These factors are described in detail in the sections that follow:

Camera requirements

Your camera should meet the following requirements in order to obtain document images that can be reliably recognized.

Recommended camera characteristics

  • Image sensor: 5 million pixels for A4 pages. Smaller sensors may be sufficient for taking pictures of smaller documents such as business cards.
  • Flash disable feature
  • Manual aperture control, i.e. availability of Av or full manual mode
  • Manual focusing
  • An anti-shake (image stabilization) feature or ability to use a tripod
  • Optical zoom

Minimum requirements

  • Image sensor: 2 million pixels for A4 pages
  • Variable focal distance

For detailed information about your camera, please refer to the documentation supplied with your device.

Lighting

Lighting greatly affects the quality of the resulting photo.

Best results can be achieved with bright and evenly distributed light, preferably daylight. On a bright sunny day, you can increase the aperture number to get a sharper picture.

Using a flash and additional lighting sources

  • When using artificial lighting, use two light sources positioned so as to avoid shadows or glare.
  • If there is enough light, turn the flash off to prevent sharp highlights and shadows. When using the flash in poor lighting conditions, be sure to take photos from a distance of approximately 50 cm.

We advise against using the flash when taking pictures of documents printed on glossy paper. Compare an image with glare and a good quality image:  

If the image is too dark

  • Set a lower aperture value to open up the aperture.
  • Set a higher ISO value.
  • Use manual focus, as automatic focus may fail in poor lighting conditions.

Compare an image that is too dark with a good quality image:

Taking photos

To obtain good quality photos of documents, be sure to position the camera correctly and follow these simple recommendations.

  • Use a tripod whenever possible.
  • The lens should be positioned parallel to the page. The distance between the camera and the document should be selected so that the entire page fits within the frame when you zoom in. In most cases, this distance will be between 50 and 60 cm.
  • Even out the paper document or book pages (especially in the case of thick books). The text lines should not be skewed by more than 20 degrees, otherwise the text may not be converted properly.
  • To get sharper images, focus on the center of the image.
  • Enable the anti-shake feature, as longer exposures in poor lighting conditions may cause blur.
  • Use the automatic shutter release feature. This will prevent the camera from moving when you press the shutter release button. The use of automatic shutter release is recommended even if you use a tripod.

How to improve an image if:

  • The image is too dark or its contrast is too low.
    Solution: Try using brighter lighting. If that is not an option, try setting a lower aperture value.
  • The image is not sharp enough.
    Solution: Autofocus may not work properly in poor lighting or when taking pictures from a close distance. Try using brighter lighting. Use a tripod and self-timer to avoid moving the camera when taking the picture.

If an image is only slightly blurry, the Photo Correction tool in the Image Editor of the OCR Editor may help get better results. See also: If your document image has defects and OCR accuracy is low.

  • A part of the image is not sharp enough.
    Solution: Try setting a higher aperture value. Take pictures from a greater distance at maximum optical zoom. Focus on a point between the center and the edge of the image.
  • The flash causes glare.
    Solution: Disable the flash or try using other light sources and increasing the distance between the camera and the document.

02.11.2018 16:19:18


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