Color High Dynamic Range Imaging
Luminance-Chrominance approach

Introduction

Recently, the problem of recovering a high dynamic range (HDR) image from multiple exposures of a low dynamic range (LDR) imaging device has gotten increasing attention from the digital imaging community. The methods currently employed date back to the first half of the 1990's and for gray-scale images they are essentially mature. As far as the issue of color is concerned, all known methods operate in RGB space. This however raises some problems, since when processing the three RGB channels independently one nearly always ends up distorting the colors, thus creating a need for white-balancing and possibly more corrective procedures. From another side, much of the processing in the imaging devices as well as final storage of the images is done in a luminance-chrominance space. This project presents a novel and efficient approach to color in high dynamic range (HDR) imaging. In contrast to state-of-the-art methods, we move the complete HDR imaging process from RGB to a luminance-chrominance color space. Our aim is to get a more computationally efficient technique and to avoid any possible color distortions originating from the three RGB color channels processed separately. To achieve this, we build a camera response function for the luminance channel only and weight and compose the HDR luminance accordingly, while for the chrominance channels we apply weighting in relation with the saturation level.

Experimental results

A source sequence of five images.

The five-image source sequence used in the HDR composition example.

tone-mapped image

The tone mapped result of our HDR imaging process.
Download losslessly compressed png image

Notes:

The images used in the composition are downsampled versions of the original sequence found in the Downloads section.
The original sequence was captured with a Nikon COOLPIX E4500 digital camera (4Mpixels, 1/1.8-in. CCD). The camera was clamped in a fixed vice, therefore the sequence does not require any registration. The exposure was controlled by varying the shutter speed (i.e., the exposure time) while holding all other parameters constant.
The exposure times (seconds) for the whole sequence were [2, 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000], where the shutter speeds shown in bold represent the images used for the composition of the HDR image.
We provide the full-resolution uncompressed TIFF-images as reference along with the downsampled sequence. We also provide the sequences artificially corrupted with Gaussian noise of three different levels.
For convenience, the sequences are packaged in separate zip files.

Downloads

Sequence description		Filesize
Full resolution original sequence	DOWNLOAD	42.7 MB
Downsamples sequence (complete)	DOWNLOAD	3.4 MB
Downsampled sequence (images used in composition)	DOWNLOAD	1.5 MB
Noisy sequence (standard deviation 5/255)	DOWNLOAD	2.7 MB
Noisy sequence (standard deviation 15/255)	DOWNLOAD	2.8 MB
Noisy sequence (standard deviation 25/255)	DOWNLOAD	2.9 MB
Full resolution original sequence, Nikon E4500, ISO 800	DOWNLOAD	35.0 MB
Downsamples sequence, Nikon E4500, ISO 800	DOWNLOAD	3.2 MB