Pic: Filmstreifen
Flash recordings

resolution: 512x288

aspect ratio: 16:9

format: MP4

size: 1,74 MB

frame rate: 25 fps

duration: 9 sec


There have recently been storms more often and I once had the idea to try out what comes out when you film a flash. The idea in itself would not have been so bad if it hadn't been for those stupid fields at DV material at the time. To explain this I have to go back a little:
The earlier television picture we saw every day actually consisted of two pictures, the so-called fields. Back then we had to deal with an obsolete technology that calls itself PAL. PAL specifies that a television picture must be 50 Hz and 4: 3, with a frame rate of 25 frames. The image was then built up line by line using an electron beam that was deflected. Unfortunately, the technology was not yet ready to display a full screen line by line. The televisions were so slow that when the television got to the bottom of the last lines, the top lines started to fade again. It was therefore thought that the picture was divided into two fields and each time represented only half of the picture lines. Once all the odd lines, then all even lines. Our eyes are so sluggish that they merge the two fields into a whole picture. This also creates the 50 Hz, because 25 frames per second consisting of two fields gives 50 Hz (Hz = heart, interval per second).

What does that have to do with lightning? Quite simply, since the fields are taken in succession and not simultaneously and a flash lasts only a fraction of a second, it can happen that a dark night view without flash can still be seen in the first field, while the flash in the second field appears. The result is a flash picture with dark, horizontal lines. It looked so terrible during the conversion that I immediately switched on a deinterlace filter. A deinterlace filter takes one of the two fields and tries to calculate the missing lines by means of interpolation and thus create a viewable frame. You can even determine the field that is used for the calculation. Unfortunately, this led to the fact that the flash was completely missing when determining the first field, since it only occurred in one of the second fields. When I determined the second field for calculation, the flash was there, but a previous glow that appeared in the first field had disappeared this time. So not the desired result.

So I had the fields calculated together. The editing program takes the first and second fields and uses them to calculate a completely new image. This did not really lead to the desired result, because a frame consisting of a flash-lit sky (1st field) and a night-black sky (2nd field) became a frame that was neither really bright nor really dark, so also not a satisfactory solution. Only the attempt with the option to display both fields has led to an almost satisfactory result. The editing program interpolated full images from both fields and simply set the frame rate to 50 images per second. Unfortunately, this frame rate no longer fits the required PAL standard and my TV at that time could not play the film.

So I opted for the improved slow motion solution. You can read how this solution works under the corresponding menu item under the selection menu of the video editing. Here is just a brief summary: Two films are calculated from a video with fields, each containing the first and second fields interpolated. The two films are then slowed down by 50% and intertwined like a zipper. Nice alternating. The result is a 50% slow motion that contains all the image information from both fields. This means that no detail of the flash is lost and the slow motion gives you even more time to watch the film.

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