You do not need to know any physics at all to believe that I can get the strobe effect in daylight with the naked eye. I suggest you try this, too, since I’m sure I’m not the only one with this type of wiring: When a car is going across your path, say while you’re standing at an intersection, sweep your eyes across the car, trying to notice the wheels. Sometimes, you get the sense of just one postion on the wheel, as if it’s stopped. Not because of the flickering of any lights. By the way, one of the best types of “home” strobes, is a neon AC circuit tester. You plug it in and it tells you if you have current. Its on and off’s are very distinct. Lots of LED’s in electronic devices are, and if you just pick up your clock radio and wave it back and forth, you’ll see the dotted line from it very well.
duh, I meant physiology
30 is half of 60 which is the nominal AC line frequency, and hence the frequency at which fluorescent lghts flicker. The combination of two flashing lights at frequencies which are a near multiple of each other can result in some really annoying flicker effects as the light pulses move in and out of phase with each other.
Its called Persistence of Vision, not framerate. Its about 1/30 of a second.
http://nths.newtrier.k12.il.us/academics/math/Connections/perception/retent.htm
So - having an image retained for 1/30 of a second in the retinal nerves seems to imply that during that 1/30 second, there’s only one image that can be observed, despite the fact that there can be a great deal of motion (and input from in front of the eye) during that time. Is that correct?
Yes. The eyes, altho wonderful, are not the perfect visual sensors. The Brain recieving the image isnt that hot either. Some people may be more visually attuned but more or less 1/30 of a second is a good rate.
A bullet could pass right in front of your eyes but you will never see it.
…rrrr
I meant a bullet fired from a gun…
Nope, not in the least. A given cone/rod may not be able to fire very rapidly, but you have a lot of them. Some of them can be firing at any given time. So you have continous vision and not at all in any way shape or form discrete vision like a camera.
And while I’m posting: the lag between light hitting your eyes and your brain realizing is saw something has nothing to do with the OP. The length of that time is therefore not relevant.
Compare the following: A video where the camera does a quick 180 pan in a second.* The result is unwatchable. Do the same with your head. (Not moving your eyes, when your eyes move you get a little blacking-out-of-the image effect.) No problem. Professionally done videos and movies avoid doing this in order not to upset the audience. There are a lot of similar no-nos that show up in recording that don’t matter in real life due to the discrete frame rate.
I have more than a little reservation about seeing strobe effects under natural sunlight, too.
*Do it with very high speed film or better yet CGI to get rid of blurring effects.
TV is 30 ‘frames’ per second, but it’s more accurate to say 60 ‘fields’ per second… Every 1/60 of a second contains two fields, the first field is all the odd numbered lines, the next field is all the even numbered lines of the same frame. This is called interlacing… Films are shot at 24 frames per second, but they’re projected with a 3-bladed shutter moving across the lense to give the impression of a faster frame rate.
If you see something projected at 30 fps with no interlace, you can definitely see the flicker. 24 fps film is even more obvious.
Also, the fact that TV is 30 fps is a technical decision, not at all related to the ‘frame rate’ of the human eye. It’s about the modulation of power in different locations.
US electricity is modulated at 60 Hz, so our NTSC TV standard is 60 interlaced fields per second. In europe, the electricity is 50 Hz, hence their PAL standard at 25 interlaced frames per second.