Helicon FB Tube – In-depth

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This article is intended for more in-depth understanding of the Helicon FB Tube operation.

So Helicon FB Tube is being mounted between the camera and the lens. Just as the lens, the tube has contacts serving for the camera to pass through the commands and to receive data.

It’s always the camera that initiates communication. In particular, it means that neither the tube, not the lens can “force” the camera to perform any action (for instance, to make a shot).

Normal dialogue between the camera and the lens consists of lens status queries and control commands.

In response to the status query, the lens communicates to the tube the data on its name, available aperture etc. If the camera display shows the aperture value of F0, it means that most likely the lens gave no response to the status query.

Control commands include changing focus, aperture etc.

The tube is being included in the process of communication between the camera and the lens and adds control commands for change of focus.

The tube watches the communication between the camera and the lens and tries to determine when the camera makes a shot. Usually there’s a certain sequence of commands that corresponds to this.
If the tube detects that a shot has been made, the led on the tube flashes green and the lens sends additional commands to the lens to shift focus.

The first sign of correct operation of the tube is a green flash of the tube led once the camera is being turned on. It means that there’s power supply from the camera to the tube and that the tube initialization has been successful.

The second sign is the aperture value on the camera display. The correct aperture value means at least that the tube does not interfere with the communication between the camera and the lens.

The third sign is the led on the tube flashing green at each shot. This means that the tube follows the camera commands, that it detected the required sequence and has sent additional command to the lens.

Sometimes the lens does not execute the focus change commands received from the tube. Here are some of the known reasons:

  1. The step value is too small and the internal mechanics of the lens are not capable to make it. In general, every lens has such a minimum step that it can make without fail. Some lenses get stuck only at one particular point. Most likely, it happens due to the wear of parts or their contamination. In such cases, it’s better to set a big step and decrease gradually. If you put your ear to the lens you will be able to hear if the lens makes steps or not.
  2. The lens is set to manual focusing. Not all of the lenses, but some ones ignore focusing commands when set to Manual Focusing mode. For instance, original Canon lenses can execute such commands, while third-party lenses for Canon cameras can’t. That’s why for original lenses you should use the configuration method 2, and for the third-party ones – configuration method 3
  3. Focusing range on the lens does not correspond to the current focusing distance. Some macro lenses have several focusing ranges. For instance, if the switch is set to 0.38-0.55m, while the lens is being actually focused at 3 m distance (according to the lens scale window), the lens may ignore focusing commands. Normally we’d recommend to set the switch to FULL, i.e. full focusing range.
  4. The lens has no internal focus motor. Some lenses for Nikon cameras support autofocus, but has no built-in motor (e.g. AF-D), totally relying on the camera motor. Of course, the lens can’t execute focusing commands. AF-D lenses that has a built-in motor exist, however, we have no proven information on compatibility with the tube.

Configuring the tube

The tube has no information about the current lens aperture. This data is not being transferred from the camera to the lens or vice versa. Nikon cameras has a special selector to adjust the aperture value. So the value of the step sent from the tube to the lens has to be re-set with each change of aperture.

Helicon FB Tube has an integrated IR receiver that receives commands from the configuration device, i.e. smartphone, tablet or desktop computer. An IR transmitter is inserted into the audio input of the device and transforms audio signals into flashing of the IR diode. This control method can be found in many household devices, for instance, TVs or air conditioners.

Energy of the audio output is not sufficient to transfer signal over large distances, that’s why we recommend to hold the IR transmitter as close to the IR receiver on the tube as possible.

Once the tube receives a command with a new step value, it flashes green confirming the receipt. There can be a few reasons for the led on the tube not to flash green:

  1. The camera went to sleep mode and the tube receives no power supply. In order to avoid this, the camera should either be set to Live View mode or you should half-press the shutter button every several seconds.
  2. The signal of the IR transmitter is too weak. This may happen if the transmitter is positioned too far from the IR receiver. It’s important not to misrecognize the receiver on the tube (raised and dark) with the led (flat and light).
  3. Audio signal of the device is too weak for the IR transmitter. First, check that the volume of the audio output is set to its maximum. Then, make sure that mono mode is off. You can check if the IR transmitter operates correct by viewing it in dark conditions during configuration through a Web camera or a smartphone camera. Some cameras have IR filter, so we’d recommend to view other IR remote controls to check the camera.