1. November

    November Member

    We should have someone go outside, set up a blinking LED a half or three quarter miles down the road, set the shutter speed for five seconds, in the dark, with nothing but a street sign in the close distance, leave the flash on, and see what happens.

    We will not even concern ourselves with the nonsense of having a blinking LED in the middle of a dark desert road -- for no apparent reason -- at that particular time - when the photograph was being taken.

    And don't forget to jiggle the car you set the camera on, (prior to the shot), once -- with an almost imperceptible 2.5 earthquake. See what happens with the street sign (jiggle the street-sign, simultaneously with the car) -- and just see if the photograph can be recreated.

    Maybe "Myth Busters" can figure it out. (Even tho there is no myth, it's just a curiosity,)
    Last edited: Dec 12, 2013
  2. cloudspotter

    cloudspotter Senior Member

    As per Mick's photo of his scanner on a 0.4 second exposure?
  3. Mick West

    Mick West Administrator Staff Member

    A camera flash has a duration of about 1/5000 of a second. The street sign, and the road are ONLY lit by the flash, so they appear stationary.

    The suggestion of small red LEDs was initially made thinking the camera might be inside the car. Your subsequent descriptions made it seem more likely it was outside, and hence the lights were probably some way down the road - something of the size of brake lights of a car at the intersection.

    You keep calling this a dark desert road, and yet there are occupied houses all around it, and at that intersection. It's not entirely out of the realm of possibility that the source of the lights (which might only have been on for a fraction of a second) was some local person.

    I keep meaning to try some recreation, but it always seems to be light when I come accross this thread.
  4. M Bornong

    M Bornong Senior Member

    Because the flash froze the sign, your shutter was open for longer than the light created by the flash. The something creating it's own light in the distance can still move. The photo that Mick posted of his scanner demonstrates this. There is no blur of the scanner, the LED shows movement. In my photo, the speakers in the back ground show no movement, , Sean's face and body are for the most part clear, frozen by the flash, the stage lights provided enough light to blur the movement, and the LEDs on the PA were intense enough and flashing to provide that red dotted streak.
  5. Mick West

    Mick West Administrator Staff Member

    Here's another example, using a flashlight with a strobe function (rapid flashing).

    Here's the setup, taken with a normal exposure:

    And here it is with a 0.5 second exposure, (f22, ISO 100 to simulate night conditions).

    Note the shoe, the colored pad, and the floor do not move, yet the (stationary) flashlight leaves a segmented trail.
  6. Mick West

    Mick West Administrator Staff Member

    Here's the same exposure, but from a distance with flash. Notice the reflections on the globe and the skateboard do not move (as they are illuminated by the flash), yet the strobing light does.

  7. Mick West

    Mick West Administrator Staff Member

    Here's a scene in daylight, about 30 feet away, flashlight is on the left armrest of the seat.

    Here's what happens when the camera is moved during a 0.5 second exposure.
  8. Mick West

    Mick West Administrator Staff Member

    I've added "+ flash" to the "likely" part in the title, as it's an important part of why the background and sign do not move, but the flickering light does.

    And note it's just a "flickering light", it might not be LED.
  9. Mick West

    Mick West Administrator Staff Member

    Update, I was out at night with my camera, so took a photo of this scene without flash, just hand held.

    Then with flash, holding the camera as steady as I can. Notice the number plates and street signs are brighter and sharper.

    I then took the same photo, but this time with flash, and moved the camera.

    Notice the number plates, and the street signs do not move, but the lights do move. Now while this is not a dark desert road (it's Windward and Ocean, in Venice California), it does illustrate some of the effects in the original image, in particular the road intersection marker in the distance is well lit, but does not move.

    And while most of the lights are not flickering, some are, and leave evenly spaced dashes, as seen in the original photo.
    They are not particularly long or spaced out as I unfortunately did not move the camera fast enough, but it illustrates the principle.
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  10. Glad I'm Me

    Glad I'm Me New Member

    To the author of the above: Back in the days when cameras used rolls of film and needed to be developed I had many times experienced pics coming back with things like this on them. It was due to bad film or something scratching the negative or the film while being processed. Even a tiny speck of water on the lens can cause all kinds of weird images to appear on the finished pic. Now about what is written above , you state you were taking a pic of the glow over the mountains yet you later say the hills were dark and that there were no houses or roads where you were at yet you think there is a street sign in the foreground . In the pic it also shows an obvious asphalt old road.
  11. Elfenlied

    Elfenlied Member

    I don't think there were LEDs or other lights in front of you, I'm more interested in whether there was a light behind you. A shutter could stay in the open position, due to a defect, something jammed, or accidentally the wrong exposure time chosen. So you take the picture, the flash lights up the road and street sign, then it's dark again. The shutter stays open, but it's dark in front of you so that's ok. You pick up the camera, and do whatever you did.. All that's needed is one light visble from that spot, and your camera lens pointing in the right direction for half a second, maybe while you were putting on the lens cap, something like that.
    However, given that the line ends abruptly in the middle of the picture, it must either be the shutter closing at that moment, or the light turning on or off; the lens cap wouldn't move fast enough, you'd see the line fading, not suddenly ending.
    Of the remaining options, the shutter closing is way more likely than a light appearing or dissapearing at that exact moment.

    If that light was a sodium street light or some other gas discharge lamp, you'll get dashed stripes on your picture. Google gave me these two examples of what i assume are low pressure sodium street lights.

    [​IMG] [​IMG]
    When you use a flash at night the picture usually has strong contrast, and the black is real black. The lack of contrast in yours (unless that's a scanner artefact) might also be explained by long exposure to the little amount of light from the night sky, the movement of the camera would average out the differences.
    Last edited: Dec 23, 2013
  12. Mick West

    Mick West Administrator Staff Member

    Another example of street lights leaving the dashed lines

    (a long and a short exposure overlaid, so you can see the background)

    I think the solid while lines are from newer non-pulsing LED light.
  13. Rns

    Rns Member

    It looks very much to me like a car in the distance with it's hazard flashers on with a long exposure and camera movement during the exposure.

    The colors add up (orange yellow)

    If you look closely you notice that the blinking period is not as stable as a modern solid state controller but sloppier like a thermal flash rate of a car module of that era.
    Last edited: Feb 13, 2014