The APORIA 2/24mm is a very short, large aperture Gauss type wide angle lens with a length of 5.8mm, and weight of 45 grams. It was designed to be amazingly small, in sharp contrast to current large and heavy retrofocus lenses. A weakness of Gauss type lenses is coma flare from mid frame into the corners causing reduced contrast and peripheral light falloff, and I struggled to improve this, but was able to bring it to a satisfactory level of performance.
High refractive index low dispersion glass with an nd of 1.8 was used for the large front and rear lens elements, keeping lens length down to 12.8mm and reducing peripheral light falloff. In regard to astigmatism, sagittal and meridional lines overlap perfectly out to ⌀35 as shown in the AST chart, and the image is totally devoid of swirly character. However, this results in strong curvature in the image field.

-0.18 of a large aperture lens. The ~ in the MT chart is due to the changing point of focus

​A 0.3mm is roughly double the from the curvature. This characteristic must be duly taken into account when making photographs. As depth of field increases from f4~5.6 and smaller it becomes un-noticeable.
Probably the most attractive qualities about this lens are it’s inconspicuous body cap size, and it’s large depth of field, lending itself to capturing the lively activity of people in the city.

LENS SPECS

Formula: Gauss type, 6 elements in 4 groups.

FL: 24.5mm, F no.: 2.08

Mount: Leica M, 28mm frameline

Focus: ∞~0.5, rangefinder coupled to 0.8.

Filter: M34 glass only

⌀50, length 5.8. Weight: 45g