In reply to <a href="https://www.pencilofrays.com/double-gauss-sonnar-comparison/#comment-5275">Jason Lane</a>. Hi Jason, thank you for the comment! Yes, I agree that the Petzval lens is a great design to explore as a starting point. I see the Petzval form in the rear component in some zoom systems. The Double Gauss design gets featured everywhere as the standard lens design, but the logic within this lens is not straightforward. I suspect that the two negative lenses (cemented lenses) facing the stop are to blame for the tight tolerances. With the cemented lenses of the Sonnar, one can expect a high degree of precision in the cemented glass, leaving the alginment up to three lenses compared to the Double Gauss' four.