30/5/2013
Hello, World
It's been almost a month since my brother returned from the USA with tons of new stuff for me. One of the most exciting of the goodies was a new camera - the Nikon D7100. Along with it came a 10-24mm f/3.5-45 lens.
Anyway, fast forward to yesterday. I was prepping to record a video at my music school for a band performance. I had spent the previous night researching video recording. Shutter speed in an open sensor digital video recording system? What the hell. That's when I learned about the rotating shutter mechanism, which explained a question I had asked myself years ago but never bothered to find the answer to: who did the film reel camcorders work? The rotating shutter blocked the reel between frame switching. I still haven't grasped the whole concept yet, though. My main confusion is on the matter of how the reel moves. From the movies and videos I have seen, the reel rotates continuously. However, in the case of a rotating shutter, the motion of the film has to be jittered, pausing between shutter "releases". I guess that's a mystery for another night, or another experience.
But I digress. Back to the topic at hand, I had, thanks to my recently-acquired knowledge, shifted from 720p60 to 1080p30. I had managed to get the ISO all the way down to 1600 from 6400 in the limited light. This was in part due to the application of the recent awareness, and partly thanks to the new white, 23w CFL lamps in the room, which replaced the dim, yellow, most-likely-6W CFLs. Well, the quality was quite smooth. There was just the right amount of motion blur with a 360° shutter. There was little noise and the sharpness was adequate. However, there was a new issue: there was a weird horizontal flickering when viewed on the big screen. I tried adjusting the shutter speed as well as the ISO, but that didn't help. Finally, I tried switching off the tube light. Still futile. I resolved to work the issue out at home.
That brings us to my research half an hour ago. I would be lying if I said that I wasn't surprised by the mention of "PAL" and "NTSC" in video frame rates. Analog signals. What perplexed me was the rationalisation of the flickering on the analog region. How could the geological location of a digital camera cause flickering in the video and require one to change the frame rate of the video? Well, I went with it and tested it out on my own. And viola, no flicker at 25 and 50 FPS. Furthermore, particular shutter speeds at 30 FPS (1/50 and 1/100 to be specific) removed the flicker too. After that, it was just physics and general knowledge.
Alternating Current! That was the cause. In PAL countries, the frequency of the A/C current is 50Hz. In NTSC countries, it is 60Hz. I guess that is the origin of the specific analog signals. Due to the sinusoidal alternating nature of the current, our lights flicker at 50Hz. With a frame rate of 30 or 60 FPS, the dimming is caught in certain frames, causing horizontal flickering glitches. A workaround is to use the aforementioned particular shutter speeds.
Sometimes I forget how much there is still to learn in this world. Yet, times like this serve as constant reminders. But for now, that's that. I'm going to be recording tomorrow at 1080p25 and a lower ISO than previously considered. I can even consider a 180° shutter, but I suppose that would be pushing it.
Goodnight
