I'm planning to create a customized aperture effect. Like this one in the Photo.
I'll be doing a DIY customized aperture that will be attached to the filter. My lens' widest aperture is F/1.8 and so that will be also the widest f-number of my customized aperture or if that's not possible, then the widest possible smaller than 1.8 will be. But I also want it with different f-numbers also, like F/2.8. So my question is What are the diameters of the lens' aperture in physical sizes? (e.g. mm, cm or inch) Do we have any formula for that? My focal length is 35mm if that information is needed.