Canon Patent For Star Tracking in Astrophotography

Egami (translated) spotted another patent filed by Canon.

The patent refers to a technique for the generation of sharp images without star trails when taking photos of the night sky with long exposures. The purpose is to generate an image where a landscape and a star are made bright and a track of the star is prevented from appearing when a star and landscape photograph is taken.

How does this work? A first detection process concerns the landscape in the test image, first detection data is produced. A second detection process detects the star from the test image in accordance with the first detection data and obtains second detection data. The exposure condition setting section obtains a first image by the imaging section with a first exposure condition which is set in accordance with the first detection data, controls the imaging section with a second exposure condition which is set in accordance with the second detection data, and obtains a second image. A first synthesis corrects a luminance value of the star to a prescribed luminance value in the second image data, and sets it to be a first synthesized image. A second synthesis synthesizes the first synthesized image and the first image, and generates a second synthesized image.

Canon patent

• Low sensitivity, I will test taken at the proper exposure
• Place the time, to test shooting with the same settings
• From the difference of the two test images to detect a movement of the star, and also to calculate the proper exposure time from the mobile width
• The production shot with appropriate exposure to the subject of non-star
• The production shot with appropriate exposure to star
• To obtain the final output image by synthesizing two images production

[via Egami]