The Quirky Camera System: The Nikon F3AF

 

The Quirky Camera system: The Nikon F3AF

            The F3AF can be best described as a sub-system of the F3 family.  It is made up of three main parts that can also be utilized individually to a limited extent by other F3 system components.  The purpose of the F3AF was to introduce lens autofocus to the F3 system.  Along with the body with the AF finder DX-1, Nikon introduced two lenes with native auto focus motors, and a teleconverter that offered limited auto focus to a few manual focus lenses with a maximum aperture of 3.5 or larger

When the three main components are assembled, you get an F3 camera that offers passive autofocus along with the ability to use many of the F3 system accessories such as motor drives, data backs, and bulk-film magazines.

If we use today’s autofocus terminology, the F3AF’s autofocus is a single point, continuous servo, shutter release autofocus system.  There is only limited communication and control between the body and the DX-1 finder so the autofocus operation is unusual to a modern user.  Pressing the shutter halfway will signal the DX-1 to start the autofocus sequence.  The DX-1 will then operate continuously until either the AF-lock on the lens is depressed, or sixteen seconds after the shutter button has been completely released.  In more modern bodies, releasing the shutter release button stops the autofocus cycle, but not so in the F3AF.

The main system components each play a part.  The body has the smallest part.  The main distinguishing feature of the F3AF body is the electrical contacts visible inside the lens mount.  These contacts attach to wires that lead to the contacts in the finder housing that mate with the DX-1 finder.  Besides these contacts, the F3AF body is operationally the same as the standard F3 body.  The body retains the same controls, aperture priority auto exposure, flash sync, metering pattern and display, and compatibility with system accessories.  The one caveat with compatibility is you should not try to mount modern AF or AI-P lenses to the camera with the DX-1 attached.  The contacts are not compatible.  If another finder is mounted on the F3AF body, there should be no issue as the contacts don’t lead to anything.  Of course, the F3AF label on the front of the body is also a dead giveaway that you have a F3AF.

While there may have been plans for more AF lenses for the F3AF system, only two lenses and one teleconverter made it to market.  The two lenses seem to have been aimed at the sports and action set, which were the target market for the F3AF system.  The first lens is the 80mm f2.8 lens.  It was a prime made of six elements in four groups.  The HS-7 lens shade is wide enough to reverse over the lens when not in use.  The lens has the metering and aperature controls of the AIS system and then with the addition of an integral AF motor, AF lock button, manual/autofocus switch and a narrow manual focus ring.  The 200mm f3.5 ED is a slightly faster design of the 200 f4 lens and is of similar AF design as its 80mm little brother.  The 200 f3.5 offers ED glass, an integral lens shade and a multi-range focus limiting switch, both of which are missing in the 80mm lens.  The final lens offering was the TC-16 which is a 1.6x teleconverter that causes a 1-1/3^rd stop loss of light but allows limited autofocus on faster-aperture manual focus lenses.  The idea was to allow autofocus on longer telephoto lenses.  Nikon later came out with the TC-16a which worked with the F4 era autofocus bodies that gave the same autofocus capabilities to manual focus lenses.  It is important to note that while the two F3AF lenses can be used on the F4, the TC-16 cannot be used.

The final component of the system is the DX-1 finder.  This finder has an integral focus screen and houses the autofocus cells, control system, pentaprism, and autofocus status display. While the hallmark of the F# system is nearly 100% view, the DX-1 has a more limited 92% view, which is closer to the Nikkormat and FM/FE series offered at the time.  The finder requires a separate power supply and unlike the camera body, cannot be powered by attaching a motor-drive.  The finder houses a pair of AAA cells that power the finder systems as well as the autofocus motors in the lenses and teleconverter.  A corded external battery pack that uses larger capacity AA cells can also be fitted.  The original idea was that the pack can be kept in a warm pocket when shooting in cold weather, but the added battery capacity also prolongs shooting time.  The focus display is in the finder on the bottom of the display.  When focus cannot be achieved, a red “X” LED is displayed.  The in-focus indicator is a bit different than modern displays, as there is no green circle LED.  Instead of the circle, the two red triangles are displayed simultaneously.  During the focus process one triangle or the other is displayed to indicate which direction the AF lens is moving or telling the photographer which way to twist the focus ring to obtain the correct focus.  The DX-1 focus screen has a large, magnified block in the center of the screen which is where the focus point is.  The magnifier is unique to this finder.  There is also a circle in the center of the frame to indicate the 80%-meter area.  The remainder of the screen is ground glass for manual focusing.  There is no microprism or cross rangefinder features for manual focusing on the DX-1 screen. 

The one mystery about the DX-1 is the purpose of the five-pin accessory port near the battery compartment.  Social media queries of Japanese collectors only deepen the mystery as they indicate that there were no accessories made for this port.  One collector was able to send an incomplete wiring diagram.  Three of the pins look to connect to three pins in the lens mount.  They are in line with each other on the PCB and use the same color wires.  Unofficial Nikon sources reference an online blog in Japanese claims that the bottom pin, at the six o’clock position is ground; the next pin going clockwise is the focus limiting signal, next is the focus confirmation signal, the next is focus towards infinity, and the last is to drive the lens from infinity towards the minimum focus distance.  This confirms the idea that these pins are ONLY for lens control and not power.  Power to drive the lens must come externally.  My best hypothesis of this port is an unfulfilled plan to offer an externally powered super-telephoto lens that would interface with the DX-1 for autofocus control but require an external-to-the-camera power supply to move the heavier elements, something that the small AAA cells could not do effectively.  This could have been done with either an external pack along the lines of the LD-2 for the 120mm Medical Nikkor introduced around the same time, or some sort of lens with a built-in battery, although this seems far less likely considering the state of battery technology in the early 1980’s, and need for batteries for each lens being used.

While the system on a whole offers an innovative, but rather limited AF experience, the system components can be used as part of a more normal F3 system.  As previously mentioned, if you insert a normal focus screen inside the body and add any of the F3 finders, you have a fully functional F3 with a full range of manual focus lenses and the rest of the system accessories.

The two F3AF lenses can be used on any F3 as manual focus lenses, as well as any of the other Nikon manual bodies from the Nikon F to the FM/FE series.  Additionally, they can be used on the F4 and 2020 as well, even with full autofocus.  These lenses should not be used on modern bodies unless the electronics are disabled because they can rapidly drain the batteries.  The biggest issue using these lenses as manual focus is the fact that the AF motor is not de-clutched from the focusing ring with the switch.  This means the photographer needs to twist the narrow ring with more than the usual amount of torque to move both the motor and the lens elements.  This makes for an uncomfortable, and slower operational experience for the user.

The DX-1 finder can also be used on a regular F3 body.  Without the contacts, it cannot communicate with the lens or provide actual autofocus functions, the finder does offer electronic range finding.  This feature is common on modern bodies where the in-focus display confirms that the subject is in focus during manual focus.  Unfortunately, the center of the frame is magnified and not part of the ground glass, microprism, or split-image rangefinder normally found on focusing screen.  To confirm focus, you need to use the ground glass outside this magnified area.  If the rangefinder assist is working well, this is not an issue, but if the lens is too slow to use this feature, or the subject lacks the contrast needed for the DX-1 to focus, then it is a bit of trick to get the subject in focus using traditional manual focus methods. 

The F3AF sub-system was not popular, gave only mediocre autofocus performance, and is now mostly a collector’s item; but still offers a unique camera set to practice film photography