The LEICA ELMAR-M 24mm f/3.8 ASPH is an extremely compact lens, especially for such a wide angle, which also offers outstanding imaging performance. Even wide-open, it delivers uniformly excellent reproduction quality over the entire image field, only deteriorating slightly towards the edges in the close-up range. This performance can only be improved slightly by stopping down, which means that you can take photographs wide open without concerns, unless your compositional ideas call for a greater depth of field that can only be achieved with smaller apertures.
The vignetting characteristic of every optical system is naturally more pronounced on a super wide angle lens than on normal and long focal length lenses. With the diaphragm completely open, it is a maximum - i.e. in the corners of the image - of around 1.9 stops for the 35mm format, or around 1.1 stops on Leica M8 models with their slightly smaller format. Stopping down to 5.6 visibly reduces this light falloff at the image edges - to 1.4 and 0.8 stops respectively. Stopping down further does not bring about any notable reduction since essentially only the natural vignetting remains.
The lens' maximum distortion is around 1% and therefore hardly perceptible.The retrofocus-like construction is made up of a total of eight lens elements and the use of an aspherical surface and glass types with anomalous color dispersion (partial dispersion) make a crucial contribution towards restricting aberrations to an absolute minimum.
