In my understanding, this lens has a super lens with unique heavy metal content! ! Compared with swords, the famous swords of past dynasties have been completed after a lot of tempering, and so have Leica's lenses, otherwise his optical products will not be circulated for a hundred years.
As far as the imaging effect is concerned, the lens of Leica 50f2aa that we explained to him is an ultra-dispersive lens, so this lens is invincible in eliminating dispersion and distortion in the same focal length lens. Everyone has his own opinion on the effect of the film. Leica used it to appear on the cover with M-M. Leica may think that black-and-white movies can better show the talent of 50f2aa. He can find out more details than other shots, with stronger penetration and less distortion. ?
Of course, the color performance of color digital cameras will not be bad.
The explanation of Zhihu Great God is reproduced as follows:
First, let's look at its optical structure. As shown in the figure below:
Eight blocks and five groups, asymmetric double Gaussian structure, of course, you can also think of it as six blocks and four groups of double Gaussian plus one set of compensation.
From the overall structure, it is not particularly different from ordinary people. The aspheric lens in the middle of the lens group is placed in the ideal position, where the aberration is the largest and the function of aspheric surface is maximized. The application of the last two groups of thick lenses is helpful to correct the field curvature. On the whole, the overall structure is too slender and the vignetting (aperture erosion) is very heavy, which will seriously limit the edge illumination, and it is estimated that the edge illumination will not exceed 30%. Of course, in order to pursue the ultimate resolution, it is also possible to sacrifice some edge illumination. The large dark corner of the edge helps to create a certain "metaphysical" atmosphere, which may be a gain.
In fact, eight groups and five groups of F2.0 apertures are designed, which is considered as a relatively luxurious material. With such a complicated structure and aspheric surface, theoretically, the refractive index should be better. Of course, Leica didn't point out what special materials were used, and I don't have this patent document, so if Leica uses very conventional materials and only uses an aspheric surface, it should be said that it is still a classic and beautiful design.
Let's look at other data of Apo-summicron 50mm asph: the total weight is 300g, the Leica optical part is about 70~ 100 g, and the Leica edge illumination is about 23%, which is not ideal; The distortion is about 0.4%, which is excellent; From MTF, the RMS value of the central image point is about 6um, and the resolution is very, very high.
As for why it is so small, it can be said that it is relatively small because of the specifications of 50mm F2.0, the back distance of M bayonet and the double Gaussian structure it adopts. If it is designed on a SLR, the back contact distance of 38.5mm determines that it is difficult to achieve a higher quality design by using a double Gaussian structure, so it is generally considered to use an inverted telescope.
Use Codev to simulate. Under the conditions of 8 pieces and 5 groups, aspheric surface, 25mm back contact distance and the range of ordinary glass diagram, the double Gaussian initial structure is randomly selected. After about half an hour of adjustment and optimization, we can get a preliminary result that the index is close to Apo-summicron 50 asph. The root mean square dispersion circle of the central image point is about 8um, and the distortion is less than 0.8%. The edge illumination is 3 1.4%, achromatic, and the optical weight is about 90g. It can be used as a 43mm filter port, and the index is close to that of Leica. If we follow the design cycle of one to three months and consider using more expensive abnormally dispersed nitrate materials, it is believed that after repeated adjustment and optimization, it is possible to reach the index similar to Leica.
Generally speaking, if Leica uses expensive ED glass, high refractive glass or abnormally dispersed glass, there is nothing special about this structure. I don't think it is a "model of medium focus optical lens". If he can do five groups and six pieces, it is a masterpiece worth kneeling on.
For the statement of the Great God, the structural design did not meet his expectations. However, almost all the top fixed-focus lenses were created by Leica. If the structure is changed, he may have a limited edition. Then the price of this lens doubled!
Zhong bo Li ka branch