KO-120 120/2.1 is a representative of a family of high-aperture film projection lenses using a very simple aplanatic four-lens scheme, which in the Soviet tradition is called "Kinolux". If you believe the data from the "Catalogue of lenses developed at the GOI" by A.F. Yakovlev, KO lenses cost as much as 10 times cheaper than their counterparts in terms of the RO series (six-lens anastigmats)! Due to the prevalence in the secondary market, low price, compatibility with most cameras and extremely attractive parameters, KO-120 lens blocks are often used in home-made lenses of various levels of performance. For example, my first adapted projection lenses had a glued lens as a focusing mechanism. epoxy paper tube. A lens KO-120 from the review of Arkady Shapoval had a metal glass for focusing with a threaded attachment to the camera. I must say, this particular article, as well as a review of the lens F=92 LETI-60M 92/2 many years ago inspired me to study and adapt projection optics.
This article presents the KO-120 120 / 2.1 lens, fully adapted for use with modern cameras. Read also the article about short-focus aplanat KO-90 90 / 1.9, adapted for mirrorless cameras.
Optical design - 4 lenses in 2 groups, aplanat;
Focal length - 120 mm;
Relative aperture - 1: 2.1;
Frame format (calculated) - 18x24 mm (covers 44x33 mm);
Rear focal length - ~52 mm (compatible with small format SLR cameras);
Landing case diameter - 52.5 mm;
Features - in its original form it does not have a focusing mechanism and an iris diaphragm.
Design and adaptation features
KO-120 is a metal pipe consisting of two parts connected by a thread. A two-lens gluing is planted in each of the parts. The front of the lens can be used with other lenses in macro lens.
Unfortunately, KO lenses do not contain a place for installing an iris diaphragm in the body, therefore, when adapting, the body has to be made from scratch. For this reason, the adaptation of these film projection lenses is a very expensive pleasure. The adaptation procedure is completely identical to that described here и here. A photo of the adapted lens is shown below.
I also have photos of the "transitional" version of the KO-120 lens, which I used on the camera Canon 600D a few years ago: this was my first projection lens with a correctly selected and set aperture. The lens block of the primitive design was made of steel, and the focuser of the lens was used as the helicoid Tele-N 200 / 3.5.
The KO-120 is much larger than shooting lenses with similar parameters - its optical design does not provide compactness. However, the mass of the adapted KO-120 is very small even in comparison with shorter-focus projection optics of the type PO500-1 90/2. The factory-made helicoid provides comfortable focusing down to distances of about 0.7 m, which provides a good macro scale. Usually the MDF of 135 mm lenses is 1-1.5 m.
KO-120 120 / 2.1 has good sharpness in the center of the frame already from an open aperture - pronounced spherochromatic aberrations become noticeable only in the macro range. In the field of the APS-C frame, sharpness within the focal surface also does not cause much criticism at F / 2.1, but at the edges of the 36 × 24 frame, the influence of field aberrations (astigmatism, coma, chromatism) is already noticeable. At f / 2.8, however, the image quality within the focal surface is hard to find fault with. At F/5.6, sharpness is excellent.
It is important to note that the lens has a curved image field. This means that the zone of sharply depicted spaces is a spherical surface, in this particular case, the convexity facing the subject. Thus, the focus point for the edge of the image will lie closer than the focus point for the center of the image. Field curvature is usually considered a harmful optical distortion, but in some cases it can be used for artistic purposes to provide more effective blurring of the background or to build a "non-linear" composition.
The KO-120 has noticeable vignetting when used with full frame cameras. On APS-C, its contribution is negligible. When using the KO-120 with the Fotodiox EOS-NEX shift adapter to obtain images of the size "36 × 45", there were no problems with frame coverage - which means that the lens is suitable for the Fujifilm GFX (44 × 33 mm frame).
The light transmission profile of the KO-120 is typical for old single-coated optics - with slight absorption in the blue-violet part of the visible spectrum: the lens “warms” the picture a little, but most often the camera successfully copes with the installation white balance when using the lens. The contrast of the image formed by the KO-120 depends entirely on the quality of the blackening of the interlens space. Photos from this copy require little to no improvement when shooting in normal lighting, although in hard backlight the contrast drops significantly due to light scattering inside the lens block - a hood is required.
The bokeh of the lens, formed by an unusual blend of residual aberrations, is noticeably different from what can be obtained from photographic lenses of the class 135/2 . It does not look like the famous blur at all. Helios-40.
In my opinion, KO-type aplanats are one of the most interesting lenses to adapt in general, since they combine a fairly high optical quality with an amazing artistic pattern.
Below are examples of photos taken on Sony A7s, including using the Fotodiox EOS-NEX shift adapter.
Other movie projection and movie shooting reviews:
- RO3-3M 2/50
- PO 500-1 F9 CM. 1: 2 P (review from the reader)
- F = 92 1: 2
- ОКП-6-70-1 F=70 1:1,8
- LOMO RO501-1 F = 100 1: 2 (+ materials from the reader)
- LOMO RO500-1 F = 90 1: 2
- 16KP-1,4 / 65 (review from the reader)
- 35KP-1,8 / 70
- 35KP-1,8 / 75 (review from the reader)
- 35KP-1,8 / 85
- 35KP-1.8 / 120 (review from the reader)
- 35KP-1.8 / 100 (review from the reader)
- LOMO P-5 F = 90 1: 2 (review from the reader)
- LOMO P-5 F = 100 1: 2 (review from the reader)
- ЛОМО ОКС1-40-1 40/2.5 (review from the reader)
- LOMO J-53 F = 75 1: 2 (review from the reader)
- LOMO J-54 F = 85 1: 2 (review from the reader)
- LOMO OKS1-300-1 F = 300 1: 3.5 (review from the reader)
- Tair-41 50/2 (review from the reader)
- KO-120 1: 2,1 120mm
- KO-90 1: 1,9 F = 9cm (review from the reader)
- KO-120M 1: 1.8 F = 120mm (review from the reader)
- KO-120M 120 / 1.8 with a diaphragm and helicoid (review from the reader)
- KO-120 1: 2.1 F = 12cm (review from the reader)
- LENKINAP RO500-1 F = 9cm 1: 2 P (review from the reader)
- Schneider Super Cinelux 70/2 (review from the reader)
The names of the lenses correspond to their exact spelling on the body.
The projection KO-120 120/2.1 surprises with its unusual bright character of the image, which is unusual for photography optics. For such a simple optical design, the lens has excellent optical quality - in the central region of the frame it is ahead of most popular manual telephoto lenses of the 135/2 (2.8) class. I believe that these lenses could become the basis for the development of new ultra-fast creative optics, bringing at least some variety to the market of a thousand and one modifications of the "double-gauss".