Using a Digital Camera to Photograph Texts

Taking photos of documents requires some skill and practice. In this section you will learn how to set up your camera so that you can get document photos suitable for OCR. For more detailed information about the settings of your particular camera, please refer to the documentation supplied with the camera.

Before taking shots...

1. Make sure that the page fits entirely within the frame and no unwanted objects are visible.
2. Make sure that lighting is evenly distributed across the page and there are no dark areas or shadows.
3. Straighten out the page if required and position the camera parallel to the plane of the document so that the lens looks to the center of the text being photographed.

Click on the topics below to read about the required camera specifications and shooting modes.

• Digital Camera Specifications

• How to Photograph Texts

• Lighting

• Positioning the Camera

• Flash

• Shooting Mode

• Aperture

• ISO Speed

• Focus

• White Balance

• Additional Recommendations

• What do I do if...

Digital Camera Requirements

Minimum Requirements

• 2-megapixel sensor
• Variable focus lens (fixed-focus cameras, common in cellphones and hand-held devices, will usually produce images unsuitable for OCR)

Recommended Requirements

• 5-megapixel sensor
• Flash Disable mode
• Manual aperture control or aperture priority mode
• Manual focusing
• An anti-shake system, otherwise the use of a tripod is recommended
• Optical zoom

How to Photograph Texts

Lighting

Make sure there is enough light - daylight is recommended. In the case of artificial lighting, use two light sources positioned so as to avoid shadows.

Positioning the Camera

The use of a tripod is highly recommended. The best results are obtained when shooting at the maximum optical zoom. The lens must be positioned parallel to the plane of the document and look towards the center of the text.

At full optical zoom, the distance between the camera and the document must be sufficient to fit the entire document into the frame. Usually this distance will be 50-60 cm.

Flash

If there is enough light, turn off the flash to avoid the glare of the page and sharp shadows. In poor lighting conditions, try using the flash from a distance of about 50 cm, but even then using additional illumination is recommended.

Important! Using the flash for documents printed on glossy paper will cause the worst glare.

Shooting Mode

Aperture

In poor lighting conditions the recommended aperture is ~2.3 - 4.5, i.e. the maximum allowed by the camera. In bright daylight, smaller apertures will produce sharper images.

ISO Speed

In poor lighting conditions, be sure to select a higher ISO setting.

Focus

Autofocus may not work properly in poor lighting conditions. If this is the case, focus the camera manually.

White Balance

If your camera allows, use a white sheet of paper to set white balance. Otherwise, select the white balance mode which best suits the current lighting conditions.

Additional Recommendations

Insufficient lighting will cause the camera to increase expositions, which may have an adverse effect on the sharpness of the resulting picture. Try the following:

• Enable the anti-shake system, if available.
• Use autorelease to prevent the shaking of the camera caused by pressing the shutter release button.

What do I do if...

The picture is not sharp enough

The flash causes a glare in the center of the picture