> Most of the incoming light is being focused on a plane that the sensor isn't on. Indeed at 1200mm it has an equivalent f-number of 555 requiring some insanely

> Most of the incoming light is being focused on a plane that the sensor isn't on. Indeed at 1200mm it has an equivalent f-number of 555 requiring some insanely bright lighting and long exposure time to get a good image. I'm don't think that's why the lens has such a high f-number at large focal lengths. Rather, it's simply because they only manufactured a very small (1.8mm diameter) lens. Given the exotic shape and manufacturing of the lens I'm not surprised it's so small, and I suspect scaling this to larger lenses would be a very serious barrier to practicality. It's also not clear why they chose that particular focal range, so there may be some other issues I didn't notice. But on the whole this is very interesting work! The fundamental observation (not caring about the phase of light at the focal plane) that makes this work is more interesting to me tbh. The authors' previous work uses a similar technique to produce a thin, single element apochromatic lens -- something that normally takes 3 thick lenses and expensive glass formulations.