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| Topic | VIDEO: When your camera shutter rate matches helicopter rotor speed! |
| Energy Surge 12/31/19 7:18:21 PM #19 | Sahuagin posted... why not? that's exactly the kind of thing compression does to simplify the image to compress it. I might agree compression is involved in causing this effect with the tire tread. When you described a bike wheel, I was imagining a stationary observer watching the bike roll past. The stroboscopic effect is also known as the wagon wheel effect as the spokes of a wagon wheel can do the same thing as propeller blades. I didn't imagine a scenario where the camera is looking at the tire treads which are held relatively stationary in a small part of the frame because the camera is traveling with the tire. Sahuagin posted... it can't be for the bicycle wheels though since they're not moving fast enough. The speed of the wheels doesn't need to be as fast as you think. Yes, an object could turn 360 degrees in one frame to create the effect. That video appears to be 25 fps, so that would require 1500 rpm for the wheel. I agree that's way too fast. But you pointed out the edge of the tread appeared motionless while the center of the tread didn't. For mountain bike tires, the edge of the tread is often lined with a repeating pattern of studs that repeats much more frequently than the studs along the center of the tread. Let's say there are fifty studs in the tread aloud the edge of the tire just to make the math simple. Because there are fifty identical positions, it could rotate as little as 7.2 degrees per frame to match the frame rate of the camera. That's only 30 rpm. And the wheel could turn any multiple of 7.2 degrees to reach another identical position. So any multiple of 30 rpm would make the studs on the tread appear motionless. 150 rpm is around 10-12 mph depending on the diameter of the tire. The studs along center don't repeat at the same rate so the effect doesn't manifest down the center of the tread. When they reach the top of the incline they're able to move more quickly and the rate of revolution is able to match one of the speeds capable of causing the center of the tire edge to repeat each frame. So I think I'll still argue this effect is present in your linked video, though I'm not completely sure. --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
| Topic | VIDEO: When your camera shutter rate matches helicopter rotor speed! |
| Energy Surge 12/30/19 11:30:54 AM #9 | Sahuagin posted... pretty sure it's more related to compression and/or image stabilizing. I saw a similar effect watching a bicycle video where the front tire appeared to almost be motionless except for turning forward an inch or two once every few seconds. the speed of the tire should be fluctuating a lot, so it's not synchronized with the camera. the compression on the video is just reducing something that is otherwise super hard to compress due to the amount of noise involved into something extremely easy to compress since it's no longer moving frame to frame. Compression wouldn't cause this at all. It's totally the video frame rate matching a specific rate of rotation of the object. A wheel with thirty-two spokes would be a lot easier to capture stroboscopic footage of than a helicopter with five propeller blades. You just need the frame rate to match a multiple of 1/32 the rotational speed of the wheel compared to a multiple of 1/5 the helicopter blades. There are many more opportunities to match the wheel compared to the helicopter. Even if you don't match the rotational speed, the video can still appear to show a very slowly moving rotating object if you get close to the ideal amount. The the wheel wasn't completely stationary as it progressed a couple inches every few seconds, so they weren't entirely synchronized to one of those multiples of the wheel. Here's a related video on the stroboscopic effect: https://www.youtube.com/watch?v=2SgG99QKLFE --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
| Topic | The more time I watch Dark Knight Rises, the more I like it. |
| Energy Surge 09/28/19 2:07:16 AM #9 | aDirtyShisno posted... Energy Surge posted...ferko420 posted...jramirez23 posted...Marion Cotillards Woops, completely unintentional. Guess I can't edit it after an hour, deletion it is. Also shouldn't you spoil tag --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
| Topic | The more time I watch Dark Knight Rises, the more I like it. |
| Energy Surge 09/28/19 12:51:31 AM #6 | ferko420 posted... jramirez23 posted...Marion Cotillards lol. She was Miranda Tate / Talia al Ghul. --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
| Topic | No cheating, Do you know what these Chess rules mean? |
| Energy Surge 09/20/19 1:03:39 AM #16 | Yeah, those rules were in the rule book that came with the first chess set I ever had, one of those cheap plastic sets that comes in a flimsy cardboard box. The last rules I learned were the three-fold repetition and fifty-move rule. Neither were mentioned in that rule book. The only drawing situations it mentioned were stalemates and players agreeing to a draw. The ability to claim a draw under certain situations wasn't specified. So I never learned them until I played the Chessmaster PC game. --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
| Topic | New Miss Monopoly game pays female players more than male players. |
| Energy Surge 09/11/19 2:27:11 AM #45 | wolfy42 posted... Free parking doesn't give you any money, but if you land on it you get a free roll. Free parking doesn't give you any money to begin with in regular Monopoly. --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
| Topic | I felt they should have named porygon 2, porygon squared. |
| Energy Surge 07/10/19 12:50:04 PM #5 | Nah, should have been poryhedron. --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
| Topic | How many consoles do you have hooked up to your television set at the mo'? |
| Energy Surge 06/28/19 12:30:06 PM #62 | Just one, my PS2. I also have a Steam Link hooked up to the TV, but that's not really a console. --- The only reason lightning never strikes in the same place twice, is that the same place isn't there the second time. |
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