7artisans 35mm F2.0 full frame lens review (Leica M)

Material on the lens 7artisans 35mm F2.0 (Leica M) especially for Radozhiva prepared Rodion Eshmakov.

The 7artisans 35mm F2.0 (hereinafter referred to as 7artisans 35/2) lens for rangefinder cameras with the Leica M mount presented in this article is a remake of an older (2017) lens 7artisans DJ-OPTICAL 35mm F2.0, designed for mirrorless cameras, produced in 2019.

Specifications:

Optical design - 7 lenses in 5 groups, copies Voigtländer Color-Skopar 35 / 2.5 P II. The circuit does not use special elements.

Focal length - 35 mm;
Relative aperture - 1: 2;
Frame format (calculated) - 36 × 24 mm;
Field of view angle - 63° (on the calculated frame);
Focusing method - manual;
Minimum focusing distance (MDF) - 0.7 m;
Aperture control - manual, step switching;
Aperture - 10 blades;
Filter thread - 43 mm;
Lens length (from bayonet plane) – 34 mm;
Camera mount - Leica M;
Cost – ~200$.

Mechanical design of the lens

The 7artisans 35/2 Leica M mount uses a higher quality exterior finish than the mirrorless version. The body is made of silver anodized aluminum (there is also a black version), some internal elements are made of brass - therefore the lens is quite weighty - about 2-3 times heavier than the Soviet rangefinder Jupiter-12 35/2.8. You may also notice that the stupid inscription DJ-OPTICAL has disappeared from the lens (yes, in caps). But the depth of field scale remained, calculated in an incomprehensible way and, most likely, completely unreliable.

Another major change from the mirrorless version concerns the focusing mechanism. Firstly, the minimum focusing distance of the Leica M lens has been greatly increased - up to 0.7 m, which is very, very long for a 35 mm lens. Without the use of special devices, close-up shooting of small objects can be forgotten. This limitation is related to the requirements for pairing Leica cameras with the rangefinder, but it seems to me very doubtful and unjustified: for Leica digital cameras, the rangefinder is not the only focusing device. At the same time, for owners of mirrorless cameras who want to shoot with this lens, there are several interesting options that make life easier: 1) using a helicoid adapter to reduce the MDF of the lens; 2) using an autofocus adapter like Techart LM-EA to get the ability to autofocus.

Further, the focus ring travel of the lens is very small and is only 90 °. For comparison: lens focus ring Mir-1 37 / 2.8 with the same MDF, it rotates by ~270°.

Finally, the lens focusing ring itself is made completely smooth. It would be problematic to use the lens without the use of a finger pad. Yes, and with an overlay is not too great.

The aperture control ring is made much more convenient than the focus ring: it is accessible, protrudes on the body and has notches. Aperture control is made with clicks at each step from F / 2 to F / 16. The iris mechanism consists of 10 specially shaped blades (similar to Zenitar 50/0.95 E), which form a round hole with a fully closed aperture, and a regular decagon at intermediate values. This shape of the pupil makes it easy to get pronounced ten-ray stars from point light sources.

A similar solution was chosen to linearize the travel of the aperture ring (so that large f-numbers do not crowd together) - this makes it easier to place marks on the ring. Nevertheless, there were questions about the scale marking when using the lens - most likely, this lens, like many other Chinese lenses, has inaccurate, namely, “overestimated” aperture values ​​on the ring. Chinese optics at F / 5.6 - the brightest F / 5.6 optics in the world!

7artisans 35/2 uses a thread for 43 mm filters, which is infrequent among old lenses (for old Soviet lenses, popular sizes are 40.5 mm, 49 mm). The metal cover that comes with the kit is put on as a smooth nozzle, and is not fixed in the thread, which is a minus - it is easy to lose such a cover, since it is held rather loosely.

In my opinion, the 7artisans 35/2 Leica M turned out to be very controversial in design. With all the charms of an outwardly beautiful finish, the lens is rather inconvenient to use due to an unsuccessful focus ring (I didn’t even touch it later, using only a macrohelicoid), a huge MDF. And it is corny heavy for its parameters and dimensions.

Analysis of the optical design of 7artisans 35/2 Leica M

As noted above, the optical design of the 7artisans 35/2 is very close to the Voigtländer Color-Skopar 35/2.5 design, which loses 2/3 aperture stops to the Chinese lens. If you look closely at the drawings of the diagrams, you can find that 7artisans 35/2 has a very thick sixth lens, and the glued surface between the 5th and 6th lenses is also characterized by a large curvature, as well as the surface between the 3rd and 4th lenses. These features of the optical design of the 7artisans 35/2 allow the generation of higher-order aberrations to compensate for the lower-order aberrations that occur when trying to increase the relative aperture of the lens without fundamental changes in design or materials.

Measurement data of X-ray fluorescence spectra (XRFS, Bruker M1 Mistral) from the front and rear lenses of the objective shows that the objective uses conventional lanthanum crowns and flints.

Thus, large amounts of yttrium and lanthanum are well detected in the material of the front lens, which may indicate that it is made of lanthanum crown of the GOST STK3 or STK12 type.

Yttrium is not detected in the material of the rear lens, but large amounts of zinc, antimony, barium and lanthanum are present. Such a set of elements corresponds to a lead-free lanthanum flint. Given that this is a negative element, it is very likely that this is a glass with an anomalous course of dispersion, that is, a special flint. For example, CDGM H-TF8 or H-TF5.

Most likely, the original Color-Skopar 35/2.5 used similar brands of optical glasses, so we can say that the correction of optical distortions in 7artisans 35/2 is achieved by adding higher order aberrations generated by thick lenses and surfaces of high curvature. In a similar way, correction has been achieved in lenses such as Sonnar 50 / 1.5 (L. Bertele, 1930s) or Helios-40 85/1.5 and, of course, this trick does not work “just like that” and “free of charge” (I recall the shape of the Helios-40 field).

Optical properties. Comparison with Zorkiy BK 35/2.8 (Jupiter-12)

The 7artisans 35/2 turned out to be quite sharp wide open in the central area of ​​the frame. Image quality is limited by severe spherochromatic aberrations, with very strong astigmatism/field curvature, lateral chromatism, and other field distortions found at the edge of the field of view (outside the APS-C frame). The lens also suffers from barrel distortion and annoying "lomographic" vignetting.

Uncompensated astigmatism combined with field curvature played a cruel joke on this lens, as these aberrations are poorly controlled by aperture. As a result, 7artisans 35/2 is never able to form a high-quality image across a 36×24 mm frame at any aperture value. Of course, this is either a calculation error, or the lens was originally intended for APS-C format cameras, within which it is corrected very well. It is also not clear how the MTF graphs of the lens correlate with its actual behavior: the graphs do not indicate the observed strong dip in image contrast outside the APS-C frame at f / 8. However, the words of Chinese manufacturers should not be trusted at all: they have aperture It happens "lime", And CHKH charts.

Another disadvantage of 7artisans 35/2 is very poor backlight resistance. Despite a simple optical design with a small number of elements and modern coating, the lens catches flare, color fog and other artifacts very easily. As it turned out upon closer examination, there is no blackening of the counter chamfer of the fifth lens in the lens, which is located directly in the path of the light beam. Even KMZ did not allow such a thing.

Lens enlightenment also raises questions. The coating of pink, yellow and green shades is chosen in a very strange way and, on the one hand, it leads the tone to green, and on the other hand, it forms either a pink or green veil, which makes it impossible to correctly set the color balance. Moreover, even under normal shooting conditions in the absence of backlight, color rendering problems can occur because the light transmission profile of the lens in the visible range is a jagged curve with peaks in blue (450 nm), green-yellow (550 nm) and far red (720 nm, practically does not contribute to the image) areas. Ideally, the curve should be flat, without pronounced peaks (see transmission spectrum Voigtlander Ultron 21mm F1.8 Aspherical), otherwise, spurious shades may appear on the photograph, “pollution” of colors.

Overall, this is one of the worst colors I have ever owned. In many ways, it is even worse than the most odious single-coated lenses like 16KP-1,4 / 65 or 35KP-1,8 / 65 - sometimes with their help it is much easier to achieve a pleasant color, since color deviations are more “linear and monotonous”.

Faced with a lot of problems with the optical quality of the 7artisans 35/2, I remembered a similar controversial lens from seventy years ago - an early version of the Soviet lens I have Jupiter-12 35/2.8, rare Zorkiy BK (“Biogon Krasnogorsky”, original scheme - L. Bertele, recalculation by Maltsev M.D.) 35/2.8.

First, I took paired photos on a Sony A7s camera and the lenses under test, focusing on infinity at different apertures. "Vigilant" was refocused after each change in aperture due to a strong focus shift, 7artisans 35/2 has no focus shift.

Full size nimmies for 7artisans 35/2 (F/2 – F/11) and Zorkiy BK 35/2.8 are on the link here (gallery on Google Drive cloud, file names include aperture value).

Let's move on to looking at 100% crops made from the center of the image, at about a third and at the edge of the 36x24mm frame.

At F / 2-F / 2.8, the 7artisans 35/2 lens shows image quality comparable to Zorkiy BK 35 / 2.8 at F / 2.8 in the central region of the frame. At the same time, a modern lens turns out to be better at the edge of the frame, but, suddenly, worse in thirds.

With an aperture of F / 4, 7artisans is confidently ahead of the old Biogon in terms of image quality, but with an aperture of F / 5.6, the BK 35 / 2.8 has an advantage in the form of the possibility of partial compensation of astigmatism due to some defocusing.

Starting from F / 8, the size of the aberration spot for the early Jupiter-12 turns out to be small enough so that when refocusing it is possible to obtain a more or less uniform distribution of sharpness over the field, while 7artisans 35/2 does not have the ability to compensate for astigmatism at the edge of the field of view.

At F / 11, the 7artisans 35/2 still turns out to be noticeably worse than the old Soviet lens at the edge of the frame. If it had a slightly less curvature of the field, the difference would be much more impressive.

The next was to test the resistance of lenses to soft backlight. Below are shots taken with the 7artisans 35/2 at F/2 and F/2.8, as well as a shot with the Zorkiy BK 35/2.8 at F/2.8.

Surprisingly, the picture from the old lens looks more contrast and lacks large light in the upper right corner. This can only be the result of a gross error by the designer of a modern lens.

In the near field, the sharpness in the center of the lenses differs slightly, but the bokeh character of the 7artisans 35/2 is different.

Frankly, I like the blur of the old zonnar-like lens more. The bokeh of 7artisans 35/2 is noticeably distorted by spherochromatic distortions (green-blue edging of the discs, red inner part), due to the influence of higher-order aberrations along the edge of the frame, the bokeh takes on a complex look and becomes rather peculiar, intrusive. Not everyone will like this, although the aforementioned Jupiter-12 35 / 2.8 is also the same “bokenator”.

The following are sample photos taken on Sony A7s and 7artisans 35/2 with the LM-NEX helicoid adapter installed.

Conclusions

The 7artisans 35/2 (Leica M) is an outwardly beautiful, but optically weak, mediocrely designed lens with many shortcomings, the main one being the inability to provide sufficiently high image quality within a 36x24mm frame. For crop cameras (including rangefinders), the lens is a very good option, but for APS-C mirrorless cameras there are many more attractive lenses in terms of price and parameters.

You will find more reviews from readers of Radozhiva here и here.