Combined ambient and flash exposure for improved image quality

Abstract

A method for capturing an improved archival image using an electronic image capture device having a flash, comprising: capturing at least two preview images of a scene at different capture times using the image capture device; determining a scene brightness; using a processor to analyze the captured preview images to determine a motion velocity for the scene; determining a flash exposure setting and an ambient exposure setting responsive to a ratio between the determined scene brightness and the determined motion velocity; and capturing an archival image using the determined flash exposure setting and the determined ambient exposure setting.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Reference is made to commonly assigned, co-pending U.S. patent application Ser. No. 12 / 701,659 (Docket 95252) to Pillman et al., entitled “Capture condition selection from brightness and motion,” and to commonly assigned, co-pending U.S. patent application Ser. No. 12 / 943,328 (Docket 96183) to Stupak et al., entitled “Automatic engagement of image stabilization,” both of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]This invention pertains to the field of digital cameras and more particularly to the automatic use of flash and ambient illumination to capture and image with improved overall quality.BACKGROUND OF THE INVENTION[0003]Digital cameras with a multitude of operational features including but not limited to exposure control, white balance and auto focus, have been a consumer staple for decades. As camera complexity has increased, required actions by the user to operate digital cameras have also increased.[00...

AI Technical Summary

Benefits of technology

[0037]This invention has the advantage that the image quality of the captured archival image will be improved by providing a preferred balance between motion blur artifacts and image noise artifacts.

Problems solved by technology

As camera complexity has increased, required actions by the user to operate digital cameras have also increased.

None of the above-described methods are effective to reduce the effects of local motion blur.

High-grade optical elements with large apertures and image sensors with larger pixels are substantially more expensive, and are therefore not practical for many applications.

However, flashes are not effective in bright lighting and fast moving objects in bright lighting can still produce local motion blur.

In addition, flash photography is typically only useful if the distance between the flash and the scene being photographed is small.

Flash photography also tends to produce artifacts such as red eyes and very bright areas or dark areas in the captured image, which many people find objectionable.

Methods that can mitigate local motion blur are generally effective against global motion blur as well, but have the limitations described above.

However, the method of the typical camera control system 200 is prone to capture images with poor perceived image quality because the degree of brightness and motion in the scene can be highly variable and since motion is not taken into account, disappointing levels of motion blur or noise can be present in the images.

While this method does reduce motion blur in images, it does not address the combined effects of motion blur and noise in the image on the perceived image quality of the image in selecting capture conditions including exposure time and ISO.

However, the method of Rubner does not address motion related image quality issues in applications which require capturing only a single captured image.

The approach of Pozniansky et al. does not teach a method for continuously blending ambient and flash exposure for preferred exposure control.

However, no explicit motion information is used to improve scene capture, as motion estimation was not taught or used in this art.

Further, present cameras tend to switch over to only flash exposure if the scene brightness is below the threshold.

When the subject distance is large relative to the flash power available, a flash-only exposure will also be of poor quality.

Images