LED headlights and problems such as flickering movies from video with LEDs
Written by Ingo in Technology , tags: movies , LED , lights , video
For some time we have in our small home recording studio a mini-PA and some lights. In the lighting sector has in recent years done a lot. Increasingly displace the tried and tested LED lamps PAR halogen headlights. These typically have LEDs of red, green and blue, depending on the model you may have several dozen or even more than 200 such LEDs.
The advantages are clear: you can create with just a light almost any color by mixing the three primary colors according to the laws of additive color mixing. In addition, the LEDs consume little power and therefore produce no heat. Moreover, the lifetime of an LED is extremely long, so that the regular renewal deleted more expensive bulbs. Dimming is due to the built control electronics directly possible, one has to buy so no dimmer packs more.
The disadvantages of LED technology: some colors (eg blue) is beyond all doubt, while about yellow or red contribute to the halogen spots warmer. If you look at an LED light, especially when we see few strong lights with LEDs are not a homogeneous solid color, but individual LEDs of the three primary colors. This also color transitions are generated at the shadow edges.
The conventional spots are, in many cases, but much brighter - against a 500 - or 1000-watt PAR-Spot only have extreme power LEDs with an opportunity, and this still costs a few Euros more.
LEDs may flicker slightly, which is caused by the switching power supply of the control electronics. Therefore they are sometimes not for filming. Since all colors are mixed from the three primary colors, it has never been a broad spectrum, but only three individual spectral lines. This creates a certain impression of color in our eyes, which for a camera recording may, however, clearly appear different.
Some LEDs are considered kameratauglich, such as TRI-LEDs, which sit at each of the three RGB LEDs behind a common lens.
But what happens if we actually tried to film with the LEDs? This I tried during my last Youtube video, my cover of Dire Straits Six Blade Knife songs.
Cause of strong flickering
The first problem was instantly visible: he seemed on the LCD screen of the digicam with some lighting scenes one of the three spotlight not only to flicker, but to pump really is, it must light cone stretched about 2 to 3 times per second to a multiple of its size out, an effect that was seen with the human eye in any way. These pumps occurred only when the spotlight was dimmed. Apparently he then flared slightly at a rate that produced an interference with the frequency of the video recording.
For this purpose, but there was actually a solution: The effect disappeared almost completely when you shut down the option of Super Steady Shot Sony digicam. This is actually a Sony-proprietary advanced image stabilization. Alternatively, it helped to set a slow shutter, ie a closing time of eg 1 / 30 sec will be longer this time, the shadowy but movements are recorded.
Overall, it was thus possible to film the video in acceptable form. Some colors are sterile as in kind. The finished result can look at it here:
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