The Walkback Scanner is a Backlight Scanner (BLS) made by Ben D Woods Photography. Backlight Scanners were invented by legendary light painting photographer Pala Teth. They create magical light that appears to be coming from nowhere, just by walking through a scene towards a camera. This can be useful to illuminate night scenes, or add subtle light to a scene in conjunction with other light painting techniques. Australia based light painter Ben Woods has produced a commercial version of this design (with permission from Pala Teth). This review looks at the Walkback Scanner and also covers light painting techniques for using any BLS.
Disclaimer
Two Walkback Scanner pre-production versions were sent to me for testing and review by Ben Woods. The production version may have some design variations based on feedback and testing. Product links are not affiliate links.
Design and Construction
The Walkback Scanner is 3D printed on order by Ben Woods. It arrived in a cardboard box, with accessories including a cloth bag, torch/flashlight adapters (3, 6 at launch), and instructions. The scanner itself consists of a front cone (184mm diameter), rear cone, and 4 struts, which can be assembled within a matter of seconds. The retail price is AU$85 (approx. US$58 at the time of writing), with shipping included in Australia. This is very good value for money. The cost of international shipping is calculated on a case by case basis.
There are quite a few differences to the previously reviewed LACE Backlight Scanner, a BLS that has served me well for the last few years. Firstly, the Walkback Scanner has no reflective material, apparently now a design preference by Pala Teth. This results in a single cone beam with less internal reflections, instead of a double or triple cone beam due to internal reflections. It may also slightly reduce the amount of backscattered light. However, I did find that the lack of reflective material requires floody torch/flashlights (wide beam angle) for optimal light input to output ratios. The Walkback scanner has been designed to reduce plastic waste as much as possible, and most of the packaging is recyclable.
The second major change is that the Walkback Scanner uses a fixed distance between the front and rear cone, at 5cm, with 4 "blade like" struts. There are advantages and disadvantages of this. The advantages are that no screw threads are required (which eventually wear down 3D printed plastic), allowing for a theoretically improved lifespan. It also allows for faster build or pack down during transportation. The disadvantages are that you cannot adjust the distance to optimise the beam. The struts are slightly offset (i.e. not directly opposite each other) for improved stability. The blade light orientation decreases shadows in the beams compared to some other BLS designs with larger rounded struts.
I tested two pre-production versions of the Walkback Scanner. Some refinements were made between the two versions based on my feedback, which included a narrower lip on the outer cone (to reduce light backscatter) but enough to maintain structural stability, and some refinements to the adapters/connectors and input tube for more stability.
Backlight Scanner Technique
Backlight Scanners can be used to illuminate a scene alone, or used to illuminate a scene before or after other light painting techniques. The beam of light leaving the BLS is in a cone shape, and walking through a scene towards the camera (with the light turned on) will illuminate everything around the BLS. However, the BLS and light painter should be (almost) invisible. This principle works due to the front cone being larger than the rear cone, which hides the light source. It is important that the BLS is pointing roughly towards the camera during the exposure so that the cone of light does not hit the lens. I always put an LED Tea Light on top of the camera so that I know where it is in the dark!
As the front cone is larger than the rear cone, it is inevitable that there will be some light back-scatter from the back of the front cone. I would highly recommend doing the full Ninja look when using a BLS - black trousers, black long sleeved top, black gloves, and a black balaclava. I would recommend holding the BLS at arms length in front of you at roughly face height for further reduction in self illumination from light backscatter. Whilst the BLS will illuminate the path in front of your feet, you do need to keep paying attention to where you are walking. I tend to start walking towards the camera just before I turn the light on, and don’t forget to turn off the light when you get close to the camera lens! A few other things to be aware of is that the BLS may illuminate any insects flying in the path of light, as well as condensation from breath when it’s cold. I also slightly rotate/jiggle the BLS on axis to minimise any shadow from the struts.
The two below photos were taken using the first pre-production version. The production version has had some changes to reduce back-scattered light further.
The below photo was taken using the second pre-production model. The Walkback Scanner was used to add subtle light to a scene where I also created a light plant.
Torch / Flashlight Compatibility
The Walkback Scanner includes 3 (6 at launch) flashlight adapters, designed for various flashlight/torch head diameters between 25 to 38mm. Further compatibility information is linked to from the product page.
Flashlight/torches with a floody beam profile are optimal with the Walkback Scanner. My recommendations are:
Convoy S21D (519A, 60 degree BEAD) - this budget light has a wide, high CRI beam, neutral tint, tail switch with last mode memory, 2100 lumens max, and over 90 seconds until brightness step-down on full power (better than most flashlights). There is choice of 7 CCTs between 2700K warm white and 5700K cool(ish) white. I would personally recommend the 5000K option. You will need a Li-ion charger for the 21700 battery. Fits adapter number 2.
Acebeam E75 - side switch light, with last mode memory (Low to High). Double click for Turbo. Available with either 70CRI 6500k LEDs (4,500lm max) or 90CRI 5000k LEDs (3,000lm). 60 seconds until brightness step-down. 21700 battery and USB-C charging. Fits adapter number 3.
Ants On A Melon RGB Critter BT - best option for coloured light - large choice of colours (with hue and saturation adjustment), and momentary control. As RGB lights are not particularly bright, a wide aperture and/or high ISO will be required. Fits adapter number 1.
Be aware that some high powered flashlights (such as the Klarus XT11GT V2.0 (Pro)) series will step-down from maximum brightness at around the 30 second mark, which may be too limiting. Also, "throwier" lights with narrower beams that are optimal for use with light painting tools, are generally sub-optimal in BLSs. Compact flashlights have improved in power output and sustained brightness considerably in the last few years, and can outperform "soda can" sized lights from a few years ago. However, if you require compatibility with flashlights with a head diameter larger than 38mm, then I would advise considering the LACE BLS instead.
Conclusion
There are a few open-source plans available for home made 3D printed BLS. However, if like me you don’t have the time and inclination to build your own and want to purchase a proven design where the R&D has been done for you, then the Walkback Scanner is a fantastic choice. It is also good value for money.
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