The light field camera has significantly advanced conventional imaging methods and microscopy over the past decades, providing high-dimensional information in 2D images and enabling a variety of applications. However, inherent shortcomings persist, mainly due to the complex optical setup and the trade-off between resolution. In this work, we propose a Neural Defocus Light Field (NDLF) rendering method, which constructs the light field without a micro-lens array but achieves the same resolution as the original image. The basic unit of NDLF is the 3D point spread function (3D-PSF), which extends the 2D-PSF by incorporating the focus depth axis. NDLF can directly solve the distribution of PSFs in 3D space, enabling direct manipulation of the PSF in 3D and enhancing our understanding of the defocus process. NDLF achieves the focused images rendering by redefining the focus images as slices of the NDLF, which are superpositions of cross-sections of the 3D-PSFs. NDLF modulates the 3D-PSFs using three multilayer perceptron modules, corresponding to three Gaussian-based models from coarse to fine. NDLF is trained on 20 highresolution (1024 × 1024) images at different focus depths, enabling it to render focused images at any given focus depth. The structural similarity index between the predicted and measured focused images is 0.9794. Moreover, we developed a hardware system to collect the high resolution focused images with corresponding focus depth, and depth maps. NDLF achieves high-resolution light field imaging with a single-lens camera and also resolves the distribution of 3D-PSFs in 3D space, paving the way for novel lightfield synthesis techniques and deeper insights into defocus blur.