A small physics question...

[verindae]

So a friend asked me a few minutes ago why the light in these still shots of a spinning fan with active LED's appears to be emitted ahead of the rotation of the LED's.
I haven't the relevant knowledge to answer his question so I thought I'd come here and put the question to you.
There are 2 images below for clarification.
I hope someone can enlighten me on this one, thanks in advance

(Also if the links don't work let me know, not sure if they will or not)

Spoiler

Spoiler

EDIT: To fix images

 

[Veylon]

It's got nothing to do with the lights, it's your camera.

You see, to take a picture, light must go into your camera. For enough light to go in, the camera must wait a little bit of time. In that little bit of time, the spinning light has moved. Thus, the light seems to be coming from more than one place. Thus, the arcs.

The light should appear to be behind the rotation, the spinning is clockwise, right? If you're talking about the small bit ahead of the arm, it's due to the light being projected onto the clear dome with the LED's aimed slightly ahead.

 

[verindae]

It's got nothing to do with the lights, it's your camera.

You see, to take a picture, light must go into your camera. For enough light to go in, the camera must wait a little bit of time. In that little bit of time, the spinning light has moved. Thus, the light seems to be coming from more than one place. Thus, the arcs.

The light should appear to be behind the rotation, the spinning is clockwise, right? If you're talking about the small bit ahead of the arm, it's due to the light being projected onto the clear dome with the LED's aimed slightly ahead.

Thanks for the reply, yes the motion is clockwise and I get why cameras delay in image capture causes the trail to appear behind the LED, it's the projection that appears before them that has me a little stumped, it can't have anything to do with the plastic housing because it's not a solid shell, It's segmented so there's more open space than plastic and the light is visible outside of what is covered by it.

I think it's possible that the light curve is from the prior revolution and has nothing to do with the current position of the LED arm. That's just a guess but it sounds plausible enough, any thoughts?

 

[GRoXERs]

It's got nothing to do with the lights, it's your camera.

You see, to take a picture, light must go into your camera. For enough light to go in, the camera must wait a little bit of time. In that little bit of time, the spinning light has moved. Thus, the light seems to be coming from more than one place. Thus, the arcs.

The light should appear to be behind the rotation, the spinning is clockwise, right? If you're talking about the small bit ahead of the arm, it's due to the light being projected onto the clear dome with the LED's aimed slightly ahead.

Thanks for the reply, yes the motion is clockwise and I get why cameras delay in image capture causes the trail to appear behind the LED, it's the projection that appears before them that has me a little stumped, it can't have anything to do with the plastic housing because it's not a solid shell, It's segmented so there's more open space than plastic and the light is visible outside of what is covered by it.

I think it's possible that the light curve is from the prior revolution and has nothing to do with the current position of the LED arm. That's just a guess but it sounds plausible enough, any thoughts?

That's probably what it is. I have a question that might help figure out what's going on here though - is the fan itself spinning? I mean, it's obvious that the light bar is spinning, but what about the fan? If not, that could explain how they're sharp but the light bar is slightly blurry. Also, if you notice, the fan blades do not reflect the light, indicating that something (the light bar) is between them and the light source when the lights are shining. Pretty sure that itself indicates that there aren't lights suddenly appearing

 

[verindae]

It's got nothing to do with the lights, it's your camera.

You see, to take a picture, light must go into your camera. For enough light to go in, the camera must wait a little bit of time. In that little bit of time, the spinning light has moved. Thus, the light seems to be coming from more than one place. Thus, the arcs.

The light should appear to be behind the rotation, the spinning is clockwise, right? If you're talking about the small bit ahead of the arm, it's due to the light being projected onto the clear dome with the LED's aimed slightly ahead.

Thanks for the reply, yes the motion is clockwise and I get why cameras delay in image capture causes the trail to appear behind the LED, it's the projection that appears before them that has me a little stumped, it can't have anything to do with the plastic housing because it's not a solid shell, It's segmented so there's more open space than plastic and the light is visible outside of what is covered by it.

I think it's possible that the light curve is from the prior revolution and has nothing to do with the current position of the LED arm. That's just a guess but it sounds plausible enough, any thoughts?

That's probably what it is. I have a question that might help figure out what's going on here though - is the fan itself spinning? I mean, it's obvious that the light bar is spinning, but what about the fan? If not, that could explain how they're sharp but the light bar is slightly blurry. Also, if you notice, the fan blades do not reflect the light, indicating that something (the light bar) is between them and the light source when the lights are shining. Pretty sure that itself indicates that there aren't lights suddenly appearing

Yeah the whole thing is spinning, fans and light bar. I figured that's what was going on, the camera that took the picture is a high quality digital SLR camera, it's good at taking stills of fast moving objects, but even one of those has it's limits. I doubt there's much in the consumer market that can take a perfect still of a 2000+rpm LED and not get that motion effect

EDIT: I neglected to clarify with my friend about the lights but I think it's the same as mine, where the LED flickers to get that broken effect in the light. I imagine that clears that part up somewhat.