Over on YouTube [Applied Science] shows us how to make an f/0.38 camera lens using an oil immersion microscope objective.

The f-number of a lens indicates how well it will perform in low-light. To calculate the f-number you divide the focal length by the diameter of the aperture. A common f-number is f/1.4 which is generally considered “fast”.

We are told the fastest commercial lens ever used had f/0.7 and was used by Stanley Kubrick to shoot the film Barry Lyndon which was recorded only with candle light.

A microscope objective is a crucial lens that gathers and magnifies light to form an image. It plays a key role in determining the quality and clarity of the final magnified image produced by a microscope.

In this case the microscope objective is optically coupled to the CMOS image sensor using a drop of oil. The oil has better refractive properties than an air-gap. In order to get the closest coupling possible the protective glass sheet on the top of the image sensor was removed. This process resulted in a lot of broken image sensors! Apparently the yield was only two working image sensors from eight attempts at removing the glass.

Of course we’ve seen f-number hacking here at Hackaday before, such as with the A Low F Number Lens, From Scratch which achieved f/0.5.