Diffractive optical elements (DOEs) assimilate optical functionality within thin (≤100 μm), lightweight films. With the recent advent of high dynamic range two-stage photopolymers, gradient-index volume DOEs can now achieve diffraction efficiencies competitive with conventional surface-relief DOEs, while also offering the advantages of contact-free, selfprocessing optical recording into a flat film that can be laminated between protective sheets. Here we design and fabricate Fresnel lenses with what we believe to be the highest reported diffraction efficiencies achieved to date using this gradientindex DOE approach. Our analysis demonstrates that these high diffraction efficiencies are crucially enabled by the high index modulation of the photopolymer, Δn < 0.01. Another factor enabling high diffraction efficiency is the pixel count of the recording exposure. Thus, we use a photolithographic chrome mask with 9000 × 9000 pixels of 2.5 μm diameter, significantly exceeding the pixel count available from spatial light modulators. The mask is imaged onto photopolymer films of 50 μm thickness, and Fresnel patterns of up to 23 mm diameter are recorded in one-shot exposures. The resulting lenses range from f/44 – f/79 with diffraction efficiencies up to 83%. The performance of various lens designs is validated by an analysis showing that, for a given Δn, there is a fundamental trade-off between low f/# and high diffraction efficiency. This high performance represents an important step toward practical applications, ranging through solar energy concentrators, customized vision optics, integrated photonics, heads-up displays, and hybrid lenses.