I do not have the device itself (only the lens) and there is very little chance that it will ever appear. Therefore, I will give a brief information on Zenit-D in this review.
Zenit-D was produced at KMZ in 1969-70. The full name of the device is "Zenit-automatic machine D". The letter "D" in the title from the surname of the engineer from the State Optical Institute (GOI) I.A. Derzhavin, whose developments formed the basis for the automation of the apparatus.
Zenit-D was able to automatically control exposure with aperture priority. The Kiev-10 device, which also controlled the exposure automatically, began to be produced earlier, in 1965, but it has exposure priority and a selenium photocell.
The Zenit-D automation on a photoresistor was more complex and potentially more functional. For those times, the capabilities of the device were simply fantastic.
Visually, Zenit-D is not much like the classic Zenith. More precisely, it doesn't look like it at all. Photos of the device are taken from the network.
The Zenit-D shutter is generally similar to the Zenit-7 shutter. The shutter speeds were from 1/2 to 1/1000 and B. Intermediate shutter speeds were allowed.
In automatic mode, the range was narrower - from 1/30 to 1/500.
Sync speed - 1/125.
Exposure meter - in-chamber with a photoresistor. Aperture priority auto exposure. Film sensitivity range - from 16 to 500 GOST units.
The device made it possible to use the previously released optics with M39 and M42 threads without "mogal" while maintaining the automatic mode and even with metering at an open aperture.
In this case, the working value of the aperture must be entered into the chamber with a special lever from the bottom of the apparatus. The selected aperture is displayed in the viewfinder field of view.
The power source is a built-in battery of four D-0.06 nickel-cadmium batteries with an external charger.
With discharged batteries, the functionality of the apparatus was preserved, except for automatic control of exposure.
The ideas put into the camera were breakthrough for that time, although there is an opinion that the capabilities of the electronic base of the device, adjusted for Soviet realities, did not provide stable and correct operation of the automation at that time.
This is probably why the device did not go into production.
Finally, consider the lens.
Helios-44D 2/58 with D mount
Visually and structurally, the Helios-44D is very similar to another rare lens of those years - the Helios-44-7 (a staff for the Zenit-7 apparatus).
The focusing and aperture control rings have different knurling patterns, but otherwise everything is the same. From left to right: Helios-44-7, Helios-44D, Helios-44M-4.
Both lenses have a bulky and inconvenient diaphragm tutor mechanism. From left to right: Helios-44-7, Helios-44D.
The blinking diaphragm drive mechanism is also similar. From left to right: Helios-44-7, Helios-44D. The pusher looks exotic, but it is compatible with mass lenses with a blinking diaphragm on the M42 thread.
The lens has 2 unique points:
The first is its fastening. The lens is designed for D mount. This is an external mount, therefore the lens has a rotary ring with slots for three bayonet blades.
When installing the lens, it is necessary for a special screw in the rear end of the lens to hit the bayonet bit. This prevents the lens from rotating around its axis. After that, the flare nut at the base of the lens is rotated and the lens is fixed.
There is very little information about the D mount, as well as about the Zenit-D device itself. In the instructions for the device, the issue of lens attachment is described superficially.
But, if you look at this photo from the network, then you can reasonably assume that the mount on the device is similar to that on the Zenit-7 camera.
Those. the mount, which is directly integrated into the camera, is still the 7 mount.
And the D bayonet is part of a detachable complete adapter, on which the M42 thread is also immediately implemented.
Thus, we again have a situation when the mount of the device does not coincide with the mount of the standard lens.
The second unique feature of the lens is a special fork, with the help of which the aperture value is transmitted to the camera.
The instructions say that when using special lenses designed for Zenit-D, the diaphragm can be changed both by turning the ring on the lens and using a special lever on the body of the device.
When installing the lens, its plug, most likely, had to grip a special leash inside the unit. I suppose that for this it was necessary to translate the diaphragm ring always in one position during installation. But this is just my guess. I did not find a mention of this in the instructions.
I tried to install Helios-44D on Zenit-7. The complete adapter of the device contains an external bayonet D.
The lens was put on, but it was not fixed tightly. There is a slight backlash left.
I tried to ponder why a unique optics mount was made for the Zenit-D apparatus.
Why it was impossible to use a lens from the seventh Zenith, for example, is understandable. This lens is threaded, and the presence of a plug that transfers the diaphragm to the device excludes the possibility of rotating the lens during putting on or taking off.
Bayonet only and union nut only.
But why did the bayonet 7 not suit, which, apparently, is also available on Zenit-D?
I will express my guess. I have no confirmation of this hypothesis, but still.
As far as I know, the focal length of the 7 mount is 42 mm. This is a non-standard flange distance. To make a lens with such a parameter, you need to start from scratch - with the calculation of the optical scheme.
Apparently, KMZ did not have such an opportunity. Therefore, we limited ourselves to changing the mount of the already existing Helios-44-7 lens from the seventh Zenith. I have not found exact data, but I suppose that the focal distance of the Helios-44D lens is similar to the Helios-44-7, i.e. standard 45.5 mm.
And before the development of optics for bayonet 7, no one ever got around to it.
I will even assume that optics with a 7-mount are the rarest Soviet optics with a civilian mounting standard. Why is that? Because under the D mount you can find at least a standard lens from Zenit-D, and the mount for Zenit-7 is a threaded lens.
It is not known whether 7-mount lenses existed in nature in the form of non-prototypes.
But back to our Helios-44D.
- Focal length: 58mm
- Field of view: 40 ° 28 ′
- Frame size: 24 × 36 mm
- Number of lenses / groups: 6/4
- Flange distance - presumably 45.5 mm
- Aperture ratio: 1: 2
- Aperture scale limits: 1: 2–1: 16
- Aperture blades - 8
- Aperture adjustment - "Blinking"
- Near focusing limit - 0.5 m
- lens with camera - Bayonet D
- Filter Mount Location: Front
- Weight - 326 grams
- Single-layer enlightenment of barely noticeable violet color.
The aperture ring of my copy rotates smoothly without clicking. At the bottom of the ring is the tutor lever with a very long travel.
The lens aperture blades have 8 pieces. The petals are blued rather than blackened.
The full stroke of the helicoid is about 270 degrees. MDF 0.5 meter
Due to the plug that transfers the diaphragm to the camera, the lens cannot stand on its bottom end without a cap. I do not have a native cover, tk. the lens is most likely removed from a faulty camera, and the rear covers were not supplied with the stock lenses. Hardly any of the mere mortals have ever seen the back cover for the D mount.
That, in fact, is all.
To install Helios-44D on a digital device without obvious handicraft, I do not see the possibility, so there are no plans to test shots in the near future. But in the future they will, of course, appear!