The first lenses were simple with just a single element which had different issues where the image wasn't flat and had distortions, modern lenses remove as many of these as possible with all sorts of coatings and setups to bend the light correctly. I will be using a paper negative for my DIY camera much like the pinhole shooters, the paper will have some imperfections which is fine, I also do cyanotypes which have their own imperfections with the way the fluid is put onto the paper.
I am just looking for a simple lens setup that doesn't cost much, maximum of 3 elements and cheap to make, I am going to get various types of lenses from surplus shed, I am interested with ball lenses, those might be interesting, or indeed experiment with fluid lenses.
My idea with fluid lenses is to suspend a small pocket of fluid in a spherical bag of some sort and put it under pressure slightly, I can then add or remove the fluid to focus the 'lens' instead of moving the lens I just change the focal length of it lol.
I am thinking about mounting of the lens as well, plan is to look at getting some 50mm lenses (the close up lenses are 50mm) and then put them inside a 50mm ID pipe. I can then use another small piece of 50mm OD pipe which would go inside the other pipe and keep the elements in place - this could also allow me to add some air gaps and space them out a bit.