KO-90 - high-aperture aplanat used in 35 mm cinema projection devices as a cheap alternative to projection anastigmata series J и Ro... The youngest lens in the KO line, which also includes KO-140 140 / 2.2 lenses and KO-120 120 / 2.1... In subsequent years, the lenses were modernized, receiving the letter M to the name, while increasing aperture up to f / 1.8 for all lenses, increased body diameter for 120 and 140mm lenses, other specifications have changed slightly.
The exact characteristics of the KO-90 lens are apparently unknown: in Yakovlev's handbook, for example, the parameters of the KO-90M 90 / 1.8 lens are given, and then - with errors. The GOI catalog contains the OP-10 "Kinolux" 90 / 1.9 lens, calculated in 1939, which can be considered at least the progenitor of the KO-90.
The schematic diagrams of KO-90 and OP-10 coincide, although the exact rear focal length is rather larger for KO-90 - the lenses are not identical. Therefore, the question of the types of glass used in KO-90 also remains open, although OP-10 is striking in its simplicity - it uses the most common and common K-8 crown and the same "ordinary" F-2 flint. No ED and HR - just hardcore. However, I do not think that some kind of "high-tech" was used in KO-90: according to a similar scheme, relatively high-aperture telephoto lenses made back in the middle of the XNUMXth century.
Optical design - 4 lenses in 2 groups, aplanat;
Focal length - 90 mm;
Aperture ratio - 1: 1,9;
Frame format (calculated) - 18x24 mm (covers 36x24 mm);
Rear focal distance - <40 mm (lens not compatible with SLR cameras);
Case diameter - 52.5 mm;
Features - the lens in its original form does not have a focusing mechanism and an iris diaphragm.
Design and adaptation features
KO-90 is a tube with two glues in twist-out frames, nothing more. For full adaptation, the body needs to be made from scratch, since there is nowhere else to install the diaphragm. That is why projection aplanates are one of the most expensive lenses for conversion. Due to the short back focal length, the lens can only be mounted on mirrorless cameras - my lens has been redesigned for Sony cameras with the ability to replace the shank with Nikon Z, EOS M / R or M4 / 3.
The adaptation procedure differs little from the one described here: except that I used lens blocks without changes (except for blackening), a factory-made helicoid М58-М58 and also added a 49 mm thread for filters. Photos of the adapted lens are shown below.
As you can see, the KO-90 is much larger in size than the Jupiter-9 (even if it was with the M42-Sony E adapter) - the aplanates are very lightweight, but not compact. The rest of the lens turned out to be very convenient to use due to a correctly selected helicoid with a wide focusing ring, smooth and extended stroke, which provides high focusing accuracy and very small for such a PDM MDF ~ 0.5 m. solve with this lens. However, more on that later.
The lens is very sharp in the center of the frame already from the open aperture, but at the edges of the 36x24 mm frame, the sharpness drops sharply, and not so much because of the curvature of the field, but because of other aberrations (it looks like astigmatism): good resolution cannot be achieved even with accurate focusing. Within the APS-C frame, things are much better. You can also notice that in the full frame KO-90 darkens the corners a little. With aperture down to f / 2.8 and further, the lens becomes razor-sharp in the central area - this property makes the KO-90 attractive for close-up macro photography of flowers, insects and other small things.
Due to the strong curvature of the field of sharpness throughout the frame within the plane, it will not work - the curvilinearity of the focal surface is important to take into account immediately when composing the frame. This is especially helpful here EVI mirrorless camera: with its help it is possible to use far more than the central composition.
The lens after adaptation has a very good contrast under normal lighting conditions due to high-quality blackening, although in the backlight it sometimes “fades” from the color-distorting veil from enlightenment and “sun rain”. The color rendition of the KO-90 is not neutral, but, as it seems to me, it is very pleasant. It seems to me that KO lenses have something of their own.
A characteristic feature of the KO-90 is a swirling bokeh - a result of a combination of strong vignetting and curvature of the image field. Background blur is very different from what has, for example, Helios-40 or other planar lenses.
In general, I highly rate the quality of the image formed by the lens: in the central area of the frame, KO-type aplanates turn out to be much better than many shooting and projection anastigmata. I really like the non-trivial nature of the image. Among the obvious shortcomings of the lens, one can note the unsatisfactory image quality within the focal surface at the edges of the full frame and noticeable vignetting in the full frame.
All reviews of film projection and filming lenses:
- RO3-3M 2/50
- RO2-2M 75/2 (review from the reader)
- PO 500-1 F9 CM. 1: 2 P (review from the reader)
- LENKINAP RO500-1 F = 9cm 1: 2 P (review from the reader)
- ЛЭТИ-60/60М F=92 1:2 (review from the reader)
- F = 92 1: 2
- ОКП-6-70-1 F=70 1:1,8
- LENKINAP OKS1A-75-1 F=75 1:2 P (review from the reader)
- 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 / 65 (review from the reader)
- 35KP-1,8 / 70
- 35KP-1,8 / 75 (review from the reader)
- 35KP-1,8 / 85
- 35KP-1.8 / 100 (review from the reader)
- 35KP-1.8 / 120 (review from the reader)
- 35KP-1,8 / 120 (with aperture, reader's review)
- LOMO P-5 F = 90 1: 2 (review from the reader)
- LOMO P-5 F = 100 1: 2 (review from the reader)
- LOMO OKS1-22-1 F = 22 1: 2.8 (review from the reader)
- ЛОМО ОКС1-40-1 40/2.5 (review from the reader)
- LOMO OKS1-300-1 F = 300 1: 3.5 (review from the reader)
- LOMO OKS11-35-1 F = 35 1: 2 (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 OKP4-80-1 F=80 1:1,8 (review from the reader)
- LOMO OKP8-90-1 F=90 1:2 (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)
- GOZ “KO-140” 1:2,2 F–14cm (review from the reader)
- MP RSFSR GLAVOCHTEKHPROM PLANT №6 ★ F=7.7cm ★ (review from the reader)
- MSO USSR SSD UPP-1 ★ KHARKIV ★ F-7 CM ★
- Schneider Super Cinelux 70/2
- Meopta Meostigmat 100/1.7
The names of the lenses correspond to their exact spelling on the body.
KO-90 is a short telephoto camera with an incredibly bright, expressive and unusual picture. With it you can take a break from the restrained correctness of modern optics. Optical sins of the lens are rather its features, to which you need to get used to and learn how to use them.