Cactus LV5 Review
The Sensor
The sensor is the heart of the LV5 system, featuring the built-in V5 transmitter and most controls.
 |
| Sensor unit |
 |
| Sensor hood The supplied hood is recommended for outdoor usage in bright sunlight. |
The sensor’s optional bayonet-style hood is useful when other light sources may impede on the detection of the laser beam and/or cause unwanted triggerings. I personally only had to use it once.
Interestingly, the laser unit features the same bayonet mount as the hood so that one can lock the laser and sensor together by a quick turn. This provides a nice way of protecting the sensitive surfaces of the units during transport or storage. Unfortunately, the hood then becomes a separate part, but let’s not start niggling.
 |
| Sensor reflector Typically some scattering of the laser light within the sensor’s reflector will make it very easy to validate good alignment. |
Aligning the sensor so that it is hit by the laser beam typically requires tracking the laser beam from the laser to the sensor with some object to view its reflection. In a bright environment a black card is ideal but often one’s own hand suffices as a “tracking device”.
 |
| LED feedback The sensor’s LED lights up in several colours, steady or flashing, reporting back on the mode (trap/escape) used and the laser reception status. |
The sensor reports through its LED whether it “sees” the laser beam and one can even use the “escape” mode to get a trigger event once the alignment is correct. The LED’s position at the side is not optimal. I sometimes had difficulty seeing it and a placement at the top would have worked in all such circumstances.
Tip: Do not attempt to set up the sensor first with the intention to “hit” it with the laser beam by adjusting the laser. It is far easier to set the laser first – making a “ballpark” adjustment – and then move/angle the sensor into the required position.
The Sensor Controls
The beta sensor unit that I tested differs considerably from future production units by requiring the user to manually select the laser frequency. Production units will self-adjust and thus repurpose the “frequency switch” to a “Delay / Freeze” switch. See the “Sneak Preview” for more details.
 |
| Channel selector Sixteen channels to choose from. |
The extended feature set of the future production units also means that the wireless channel selector will also be used as a configuration control.
The selector dial is apparently the same part as used for the Cactus V5, with the first five channel numbers coloured blue. Since the LV5 only works as a transmitter and never as a receiver, coding only channel “1” blue would have made sense, but I personally don’t mind the part reuse at all.
 |
| Sensor controls The frequency selector (beta units only), mode selector, and cable plug. |
The sensor switch deserving the most discussion is the mode selector switch.
It determines whether the LV5 sensor creates the equivalent of a short trigger button press (single-shot mode) or keeps the shutter release button down, so to speak, as long as an event occurs (multi-shot mode).
An event lasts as long as the laser beam is interrupted (in trap mode) or visible to the sensor (in escape mode).
Therefore, a typical application scenario for the multi-shot mode is to set the camera to burst mode so that it keeps shooting as long as something of interest happens. This justifies the “multi-shot” moniker for this mode, even though technically it is just puts no upper bound on the shutter release time, whereas the “single-shot” mode does.
Single-Shot Mode
 |
| Capturing motion |
The single-shot mode is ideal when you do not want the LV5 to block the operation of your camera by a continued triggering for prolonged events. It is the best mode, for most applications that aim at getting the timing right for a single shot.
The exception is an image where you want to link the exposure time to the duration of an event. In this case, multi-shot mode – and typically a camera in Bulb mode – is ideal.
Shutter Lag
Whenever you trigger a camera with the LV5, you must allow for the camera's shutter lag, i.e., the time that passes between the shutter release button being pressed and the start of the exposure.
(D)SLRs, in particular, need to
- recognise the shutter release request (response times range from 10ms to over 200ms depending on the camera model),
- lift up the mirror, and
- set the lens aperture,
before the shutter can start to open. Setting the camera to manual focus is often a good idea, otherwise, the time to obtain good focus will be added as an unknown factor to the shutter lag.
 |
| Freezing action |
There are two ways to address shutter lag:
- Advance detection
Detect a moving object before it enters the frame so that it will have moved into the frame by the time the camera starts to make the exposure. - Flash exposure
Let the camera shutter open ahead of time in a darkish environment and let the actual exposure be created by a flash.
Flashes respond almost instantaneously to a triggering request. They are therefore ideal for capturing an event precisely when it happens.
 |
| Potting a red |
I had heaps of fun creating water droplet shots. Since my beta units did not support delayed triggering, I could not trigger on the drop falling down before it hit the water surface. The shutter lag of my camera meant that the whole event was over when it finally fired. I hence bounced the laser beam off the water surface so that it triggered two flashes (equipped with blue and red gels respectively) once the surface was disturbed by the drop impact.
The Snooker shot to the right is an example for combining ambient light exposure with a short flash at the end of the event to capture both movement and a sharp snapshot respectively. I created this shot without any assistance, by starting the sequence through opening the camera shutter – using a V5 as a remote camera control in my hand, (hence the shoddy cue action). The camera then recorded the movement of the balls until a flash was automatically triggered by the red target ball just before it disappeared into the pocket. Timing the flash exposure to one’s desire is just a matter of setting up the optical tripwire at the respective position.
Tip: If you see the reflection of the laser beam in your image, you can often swap the laser and sensor positions so that the laser hits the object at the side that is facing away from the camera. If the latter is not possible for some reason, removing the small red dot is easily possible with most image editors on the market, even free ones like Picasa.
Multi-Shot Mode
As mentioned before, the classic application for the multi-shot mode is a camera set to burst mode so that it fires away as long as the trigger reports something happening.
 |
| Bullseye |
However, there are also a number of speedlites that support a multi-strobe mode. The “Bullseye” image to the right was created by triggering a speedlite which created multiple flashes per second as long as the arrow blocked the laser beam. It took a number of attempts to correctly align the laser beam (and to hit the Bullseye…).
As with the Snooker shot, I had the camera in Bulb mode, opened the shutter manually with a V5, threw the dart, let the flash exposures happen automatically, and finally closed the shutter with the V5.
N.B., for both, Snooker and “Bullseye” shots, it would have been handy to have two LV5 sets. One set for starting the camera exposure (e.g., by the cue action or the dart in mid-air) and another set to fire the flashes.
The Sensor as a Remote Control
I saved the discussion of one sensor control till the end because it has a rather nice side benefit.
 |
| Welcome extra |
The standard use of the sensor’s “test” button is to check whether attached devices respond as desired.
One can make a camera produce a test shot by fully pressing the button or just make it auto-focus by half-pressing the button. Listening V5 receivers acknowledge the half-press by lighting up their LEDs, and there are further ways to validate settings.
The test button hence makes it very easy to troubleshoot a setup. When the batteries in a receiver or flash go empty, or there is some channel misconfiguration, it is nice to be able to track down such problems without adding to the shutter count of your camera.
The one sweet extra bonus that comes with the test button, however, is the fact that you can use the V5 sensor as a remote shutter release control for your camera (of course, provided you have at least one Cactus V5 transceiver and the camera release cable fitting your camera). I sometimes wished I had just one more V5 to use as a remote control because I already used up all my V5’s.
A V5 that acts as a remote control only needs transmitter functionality and a button. The LV5 sensor is therefore a great – if somewhat bulky – replacement.
