Caedes

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Image Intermissions

+mayne
01/16/05 3:32 PM GMT
I have noticed in longer exposures of moving objects that there is a even and continuous break in the path. Any ideas of why this happens?
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Darryl

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brphoto
01/16/05 6:02 PM GMT
My guess is that it's caused by the light source's alternating current, causing it to flicker (most HID and fluorescents are really pronounced) and act like a strobe.
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"If I could tell the story in words, I wouldn't need to lug around a camera."
+camerahound
01/16/05 9:22 PM GMT
Wow, you guys are GOOD!
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Which wicked witch wished which wicked wish?
prismmagic
01/17/05 1:23 AM GMT
I agree with will! Depending on the lighting an image break can happen. You also have to consider the background and reflective light on the subject. Other wise dark to light as the object moves. If the background lighting and shadows are not a constant enough the image merges and sections of it become as one related to the background especially in the realm of Digital. Digital Cameras run on a set parameters that are determined by its size and sensitivity processing parameters. An extrapolated 12.1 CCD will capture a moving image at a laser quality then a true 12.1 that is designed to take in the image as it captures it. Other wise an extrapolated fills in the holes deciding what belongs there.
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Art is the perception of the creator. Meaning is the perception of the viewer. acceptance is the perception of society.
+mayne
01/17/05 1:44 AM GMT
Well, I have come to the conclusion it is the sodium lighting that caused it. Thanks for the help:-)
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Darryl
*caedes
01/17/05 1:48 AM GMT
If we knew the exposure time then it would be an easy matter to calculate the speed of the snow flakes. That would be a suitable cross-check on the 60Hz theory. If the speed comes out reasonable (as I think it would) then brphoto's idea is probably correct.
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-caedes
+mayne
01/17/05 3:10 AM GMT
Haha, yes the exposure was 1/10 second. Have fun!
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Darryl
*caedes
01/17/05 3:18 AM GMT
Actually, I'm going to have to correct myself. We can't find the speed from that information, but I can calculate the effective shutter speed. I count 11 dots in each snow streak, so the flashing is indeed at 60Hz.
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-caedes
+mayne
01/17/05 4:38 AM GMT
I have another image taken from a moving vehicle where a road sign appears in this fashion. It is like I made multiple exposures and combined them into one all encompassing image. I hope my 4-ways weren't on;-)
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Darryl
+camerahound
01/19/05 9:52 PM GMT
*floored*
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Which wicked witch wished which wicked wish?
baparham
01/20/05 12:27 AM GMT
yeah, i agree with brphoto and caedes, that the "speckled effect" is caused by the flickering light. depending on if you are in europe or in the us the pronounced parts in the movement would be further apart in europe than in the usa. 50 Hz vs 60 Hz. i never noticed that in motion photgraphy, but it makes perfect sense now that i think about it.
-Brad
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Times fun when you're having flies. - Kermit the Frog
*caedes
01/20/05 12:40 AM GMT
Just as a side-side-side note: Only certain types of lights have this flashing effect (one that work like florescent tubes). Incandecent lamps don't do this because their light dies off too slowly when the current inverts.
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-caedes

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