Here is a render of the final design. Originally I had intended to quickly design a fairly simple lens. With only 2 days to nail the optical design, it has taken me until the end of the week to finish the analysis, housing design, technical drawing, program the CNC machine, and write up these log entries. It's a little longer than I wanted to spend on it, although it couldn't be helped due to disruptions like travelling to London mid week. I had intended to design a cooke triplet 50mm f/4. In the end the design spec was adjusted slightly to 60mm (making a fairly nice short portrait lens) due to the very short BFL when using a 50mm design.
The new design is called the alexica. 60.4 [PUSH.2'8] AC-PC (3) {0} following the naming convention I have used for all my previous designs.
- 60.4 - Focal length in millimeters followed by optimised max aperture.
- [PUSH.2'8] - This is a new convention. The optics are wider in diameter than needed for the design, in order to simplify manufacturing. As a result, although the lens is optimised to perform well at a max paerture of f/4, if you insert a wider aperture STOP disc you could potentially run the lens at f/2.8 or maybe even a little wider. The performance cannot be guaranteed at these settings, but there is nothing spotting anyone pushing the aperture open and using it at the faster speed.
- AC-PC - These are the materials, the equivalent of crown and flint respectively. I have used AC instead of PMMA to represent Acrylic because it is shorter to abbreviate. PC is poly-carbonate.
- (3) {0} - 3 elements, of which 0 are aspherical.
With everything prepared, this lens is now ready to be prototyped.
