NIKON Vibration Reduction (VR) "Keep Alive" Circuit

For TSE 2003, I used a NIKON 80mm - 400mm f/5.6 Vibration Reduction (VR) lens on a NIKON F5 camera body to photograph the eclipse from the flight deck of a QANTAS 747-400 ER aircraft over Antarctica. Using a VR lens really does help reduce image jitter and wander when observing a "fixed" target on a somewhat unstable platform.  The NIKON VR system, however, has two significant drawbacks which would otherwise impede its use in executing a fully automated imaging sequence (such as was done for TSE2003 and now planned for TSE2005).

1. To effectively use the Vibration Reduction feature, VR must be activated one second before an exposure is taken.  This is "normally" done (as I perceive NIKON envisioned how most would normally use a VR lens taking pictures via the shutter button on the camera body)  by lightly depressing on the shutter button (what some documentation refers to as a "soft touch") before pressing down fully to open the shutter.

2. Because the VR servos in the lens suck power from the batteries in the camera body when running like you wouldn't believe (well, I suppose you would), the firmware logic in the camera will shut down VR appx 830 milliseconds after an exposure in progress completes. I believe NIKON did this as a way to "protect" the user from draining the batteries (also used for the winder, autofocus, etc.) too quickly (but not an issue for the duration of TSE!).

Because of these "limitations" (or, as NIKON would say, "features") the use of VR is fundamentally incompatible with an automated exposure sequence with the sutter being controlled externally though the camera's electronic "shutter control line".  (Automated eclipse exposure sequencing by UMBRAPHILE is commanded through the camera's electronic "shutter control line", which is pin # 4 on the NIKON's MC-27 10-pin electronic control port).  What one really wants is to enable/activate the VR function BEFORE totality and have it remain active until it is shut down by user control - after the full sequence of externally commanded exposures completes.  I found this can be done with a relatively simple "VR keep alive" circuit, which is plugged into the camera body also through the MC-27 multi-pin connector, using pin #9.  Pin #9 is multi-functional, and is used to simultaneously enable:

(a) external shutter control (pin 4 opens/closes exposures externally, but must first be enabled via pin 9).
(b) autofocus (if you are using an AF lens and have the AF switched on on the lens) - likely NOT for an eclipse!
(c) Vibration Reduction (if you are using a VR lens and have VR switched on on the lens).

Basically, closing the pin 9 contact (returning it to ground) enables all three functions, just as touching lightly on the shutter button would do.

Hence, to enable VR one needs to close that contact (pin 9 to ground).  BUT, after an exposure is taken the camera will autonomously disable VR even if the contact is still made.  VR must then be "re-enabled", which would be like "tapping" on the soft-shutter button to turn it back on.  Actually, if you tap "fast enough" - which is faster then the time-out after exposure completion that the camera firmware uses to shut down VR -  it will remain up. So, I built a simple circuit to do the "tapping" for me - through pin 9 on the 10-pin camera control port.  Basically, it sends a series of "enable" pulses to the camera, just a bit faster than the 830 ms timeout interval.  I found, empirically, that if such a pulse is shorter than appx 17 milliseconds the camera will ignore it.  Likely the firmware uses some sort of "debounce" logic, and (a)-(c) above won't be enabled if you "accidentally" did a very rapid soft-touch on the shutter button.  I did find that with a pulse 23ms the pulses would be robustly recognized by the camera.  Hence the "keep alive" circuit, send a series of 23ms wide pulses (which  close the pin-9 to ground connection) every 820 milliseconds (robustly faster than the timeout interval, also by experimentation).

Why not make the 23ms pulses longer?  There is another firmware interaction - which I haven't figured out how to beat (ideas are welcome!).  When you started a bulb mode exposure (shutter open via pin 4), then send a VR enable (pin 9 closure) pulse, and then you try to close the shutter (via pin 4)  - the shutter WILL NOT CLOSE until you open the contact on pin #9.  I can only guess that NIKON did this assuming that by pressing "hard" on the shutter button to take a bulb exposure (shutter remains open while depressed) you are not simultaneously "asking" to enable VR as you would have done that before opening the shutter by a "soft touch".  This makes sense IF you are operating the camera by its shutter button - but not via the electronic interface for eclipse photography.  SO... for best compatibility with UMBRAPHILE, for example, I make the pulses robustly as short as possible.  What this does mean is that there is about a 3% chance (roughly one exposure out of 36) with an exposure sequence asynchronous with the keep alive timing, that the keep alive pulses will delay a shutter closing (and a planned exposure would be longer than desired, by the remainder of that 23 milliseconds).  For now, I live with that...

So... here is the circuit (from my notebook):

Just a few notes.

1. The 7805 is a 5 volt DC voltage regulator, so you can power this from a 9V transistor batter.
2. The NE556 is a timer chip, used here a mono-stable oscillator.  Actually the NE556 is a dual (two timer) package, you can use an NE 555 (I just happened to have a 556 when I built this).  For more information (a pretty complete on-line tutorial) on the NE555/556 see:  If you use a 555 rather than a 556, the pins are different - but the functionality identical.
3. The W171 is a 5-volt fast acting relay (the DIP-25 just refers to it being in a "dual in-line package").  The one I used was made by Magnicraft.  You can use a solid state (5V) relay or a reed replay - basically anything that can be powered at 5V and provide an open/close that is fast enough.
4. The outputs of the relay go to pin 9 and ground of the NIKON MC-27 connector.  The pinouts on that connector are shown here:

The timer cadence and duty cycle  (pulse width) are controlled by adjusting resistors Ra and Rb and capacitor C (see above NE555 tutorial).  The values given will result in the timing discussed.  This has worked with two different NIKON VR 400mm lenses - BUT you may need to tweak that with a different lens - as I do not know the robustness of the timing in the lens itself from lens to lens.  Also, I just used off the shelf components (10%-ish values) and you too may want to check what you get on an O-scope.  If VR won't come on, you probably need to increase the pulse width a bit.  If VR comes on momentarily and then goes off, you probably need to decrease the inter-pulse cadence a bit.

That's it!  Hand's off VR "keep alive" for solar eclipse photography!

That said.  Here are two other advantages.

1. Carter Roberts had written to the Solar Eclipse mailing List: "One thing to consider with the lenses with built in stabilizers is  that when the stabilizer is turned on the image usually drifts  briefly. Thus, at least on older designs of lenses, the manufacturer  typically says to turn the stabilizer off when using a tripod. Since  the stabilizer goes off every time you stop to change shutter speed  there is the potential to have smeared images. This strongly suggests  taking a bunch of shots at each setting (and hopefully use  auto-exposure bracketing to make that three different exposures) so  even if the first shot or two gets smeared the others will be sharp".

If you build this circuit and plug it in you don't have to worry about that.

2. To use external "shutter control" (as does UMBRAPHILE) on the F5 (not sure about other NIKON cameras) you MUST enable shutter control (which is a shared enable signal on pin 9 along with VR enable) no longer than 30 seconds before your first use of the shutter control.  And, that times out 30 seconds after an exposure.  If you "turn on" the "VR keep alive" circuit before totality, you also get shutter control "enable" for free.

Glenn Schneider
28 March 2005