Exposure time estimation for high dynamic range imaging with hand held camera
Vaclav Hlavaÿc · 2006
The limited dynamic range of a camera may be extended by composing differently exposed images of the same scene. The nonlinear camera has to be calibrated ra- diometrically first. We show that the calibration process can be difficult for real cameras. The improvement can be achieved if linear 12-bit RAW images are used as of- fered by modern mid-class and professional cameras. The knowledge of exposure time positively affects the radiomet- ric quality of the composed high dynamic range (HDR) im- age. This knowledge also helps in registration of differently exposed hand held shots. This contribution presents a new method for estimating exposure times from the histograms of images captured using a linear response camera or gen- erated from a RAW image. The presented method does not require spatially aligned images. The actual process of HDR image composition needs perfectly aligned images on its in- put. We present a method for registering differently exposed images captured with a hand held camera. The presented registration method enables capture of HDR images without the need of mounting a camera on the tripod. The methods are implemented in Matlab and tested on real data.