A simplified HDR image processing pipeline for digital photography

High Dynamic Range (HDR) imaging has revolutionized the digital imaging. It allows capture, storage, manipulation, and display of full dynamic range of the captured scene. As a result, it has spawned whole new possibilities for digital photography, from photorealistic to hyper-real. With all these advantages, the technique is expected to replace the conventional 8-bit Low Dynamic Range (LDR) imaging in the future. However, HDR results in an even more complex imaging pipeline including new techniques for capturing, encoding, and displaying images. The goal of this thesis is to bridge the gap between conventional imaging pipeline to the HDR’s in as simple a way as possible. We make three contributions. First we show that a simple extension of gamma encoding suffices as a representation to store HDR images. Second, gamma as a control for image contrast can be ‘optimally’ tuned on a per image basis. Lastly, we show a general tone curve, with detail preservation, suffices to tone map an image (there is only a limited need for the expensive spatially varying tone mappers). All three of our contributions are evaluated psychophysically. Together they support our general thesis that an HDR workflow, similar to that already used in photography, might be used. This said, we believe the adoption of HDR into photography is, perhaps, less difficult than it is sometimes posed to be

Digital hologram recording systems: some performance improvements

The work presented in this thesis was performed under the EU's Framework 7 (FP7) project, 'REAL3D'. The aim of this project is to develop methods based on digital holography for real time capture and display of 3D objects. This thesis forms a small subset of all the work done in this project. Much of the research work was aimed towards fullling our part of the requirements of the REAL3D project. The central theme of the research presented in this thesis is that of improving the performance of the digital holographic imaging system for its use in 3D display. This encompasses research into speed up of reconstruction algorithms, understanding the in uence of noise and developing techniques to increase resolution and angular perspective range in reconstructions. The main original contributions of this research work presented in this thesis are: A computer-interfaced automatic digital holographic imaging system employing `phase shifting' has been built. This system is capable of recording high-quality digital holograms of a real world 3D object. The object can be rotated on a rotational stage and a full 360 range of perspectives can be recorded. Speckle reduction using moving diusers can be performed to improve the image quality of the reconstructed images. A LabView based user friendly interface has been developed. Novel methods based on space-time tradeo and xed point arithmetic have been developed and implemented for speed- ing up the reconstruction algorithm used in digital holography. This has resulted in the publication of one peer-reviewed journal pub- lication and one conference proceeding [1, 2]. The in uence of additive noise, particularly quantization noise in digital holography has been studied in detail. A model has been developed to understand the in uence of noise on the re- constructed image quality. Based on this model, a method has been developed to suppress quantization noise in a memory ecient man- ner. This work led to the publication of two peer-reviewed journal publications [3, 4]. A novel method of removing the twin image has been devel- oped. Methods to increase the perspectives in holography based on synthetic aperture have been implemented. Apart from these primary contributions, the author of this thesis has also contributed in the form of assisting in experiments, creating gures for various papers, writing computer programs and discussions during group meetings. In total, 6 peer-reviewed journal papers (3 being primary author) have been published and 6 conference proceedings (3 being primary author) have been published. Additionally, 2 talks have been given at international conferences