In our previous post Digital Backdrop using a TV (Part 1) we explained how we used a light sensor in a circuit with LED strip lights to react to the video on the TV screen at the back of the layout to combat the silhouette effect caused by having such a strong light source at the back of the layout.
The light sensor acts as a dimmer switch to allow the lighting above the layout to increase and decrease in brightness alongside the video with such precision that it can even help simulate a lightning storm - and all without the need for any sort of computer brain such as a raspberry pi or Arduino, making it very cheap and very simple to implement.
Where this works really well, we were also keen to see whether it would be possible to change the colour of the light as well as the brightness. This turned out to be a little more expensive than the light sensor and LED strip light, at least it would have been had we not happened to already have what we needed. However it was still just as simple to implement.
We were using a laptop to play the video for the back scene which was connected to the TV via a HDMI cable. The laptop also has a USB-C port that can be used as a video output in the same way as a HDMI port is. We also happened to have a portable LED monitor that could be connected to said port and used as an additional screen for the laptop. The fact the screen was portable meant it was really light and so very easy to mount inside the top of the layout using just one bolt with just one small hole needed for the cable (the laptop is also powered via the same cable that the video signal is sent through).
Once the screen was mounted, we set the laptop up so that the video was duplicated on this second monitor and the result was a second light source that was perfectly synchronised with the back scene and the light changed subtly from scene to scene.
We continued to keep the existing LED strip lights in play too which does reduce the impact of the colour from the second screen, but meant that overall there was more light on the layout.
This was not the end of the story in terms of how we enhanced some of the more dramatic scenes on Bond Lane, but from this point on the development relied on us developing specific video sequences with particular characteristics. However, we do still fall back to using the duplicate screen where we are using unprepared video. In particular, when the layout is running at home we often put live webcam feeds on the back scene, duplicated onto the second screen to enhance the lighting in real time. A two or four minute video to have on a loop at an exhibition works well, but it can get a little repetitive when you have seen it a few hundred times.
In part three we will explain how we managed to make the light from the second LED screen even more vivid and increase the impact of the colours to really sell the different scenes.
