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12-31-2016, 07:56 PM   #1
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Long exposure looks like multi-exposure

I shot this at the NYE celebrations in Melbourne last night. Bulb Manual mode, 25 sec, f/8, ISO 100 (K-1 + DFA 28-105).

It surprised me to see that the "walking ghosts" seem to be discrete, rather than continuous integrations. I can only imagine there was a pulsing light-source somewhere nearby. Can anyone think of an alternate explanation?




Last edited by Paul the Sunman; 12-31-2016 at 10:43 PM.
12-31-2016, 08:18 PM   #2
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LED street lamps?


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12-31-2016, 08:59 PM   #3
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NYE celebration: Fireworks?

Street lights flickering at 50 or 60 Hz are too quick to cause this. A defective light?
12-31-2016, 09:06 PM   #4
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QuoteOriginally posted by DeadJohn Quote
NYE celebration: Fireworks?

Street lights flickering at 50 or 60 Hz are too quick to cause this. A defective light?
It was before the fireworks started. Yes, I agree, street light flicker is too fast. However, there was a big screen 200 m away that may have done it, if some pulsing (with the music?) image was showing.

12-31-2016, 09:10 PM   #5
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Almost all street lamps are non-continuous light sources.
The older bluish white are mercury-vapor, the amber are sodium-vapor, and now the latest are LED sources. And in other places like Las Vegas or Hong Kong where there is a lot of signs or shops, it could be neon or fluorescent.
They strobe quick enough that we donʻt see flicker, but long exposures with movement show it.
12-31-2016, 09:35 PM   #6
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Keep in mind an exposure isn't continuous. I don't know about the K-1 but IIRC the Q line went from 1/13s to 1/30s at some point. Whatever exposure time you set (aka shutter speed) the sensor will always scan multiples of that time. 1/500? Great, fits into one scan. In 2 seconds, however, thr camera will perform multiple scans. That probably combined with the strobing to produce your effect.

That's at least how I understand it, I may have gottrn something wrong, so feel free to correct me. And happy new year!
12-31-2016, 09:43 PM   #7
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QuoteOriginally posted by Giklab Quote
Keep in mind an exposure isn't continuous. I don't know about the K-1 but IIRC the Q line went from 1/13s to 1/30s at some point. Whatever exposure time you set (aka shutter speed) the sensor will always scan multiples of that time. 1/500? Great, fits into one scan. In 2 seconds, however, thr camera will perform multiple scans. That probably combined with the strobing to produce your effect.

That's at least how I understand it, I may have gottrn something wrong, so feel free to correct me. And happy new year!
The OPʻs shot is 25 seconds. With any DSLR, that is a continuous 25 second exposure. Shooting video would involve multiple frames per second.
01-01-2017, 12:43 AM   #8
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It could be due to the people walking speed. Given an exposure time and a filed of view, the minus the speed of the moving object, the more is the time that the object could be exposed in the same position thus be visible. Better try with a ND filter on and a longer exp. time. People slow down and stop, then restart when walking around. My 2 cents. Happy new Year to all.

01-01-2017, 03:54 AM   #9
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LED streetlamps, whose duty cycle is phasing in and out of sync with each other possibly. Individual duty cycles are too fast to see at human scales.
More likely, the people were pausing, slowing, speeding up...moving into light and into shadow, so on.
01-01-2017, 06:14 AM - 2 Likes   #10
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Your shutter speed is far too long to cause any troubles with pulsing lightsources (or lets say light that is pulsing so fast you can't see it with your free eyes).

I think those "discrete ghosts" happend because of the nature of the movement: taking a step forward is a more complex movement than for instance a rolling car. Lets say you just look at the feet: one is on the ground (motionless) and the other is swinging by, for the next step it's the other way around. So the movement of the legs is not a continuous but rather a repeating motion. The upper body has a more continuous motion but you (or whoever) might swing his/her arms during walking. Depending on the angle of the arm or leg and the positon of the lightsource they reflect sometimes more light than other times. I think the combination of the arm/leg position to the lightsource and the repeating pattern of walking causes those "discrete ghosts".

Last edited by othar; 01-01-2017 at 08:17 AM.
01-01-2017, 12:47 PM   #11
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QuoteOriginally posted by Giklab Quote
Keep in mind an exposure isn't continuous. I don't know about the K-1 but IIRC the Q line went from 1/13s to 1/30s at some point. Whatever exposure time you set (aka shutter speed) the sensor will always scan multiples of that time. 1/500? Great, fits into one scan. In 2 seconds, however, thr camera will perform multiple scans. That probably combined with the strobing to produce your effect.

That's at least how I understand it, I may have gottrn something wrong, so feel free to correct me. And happy new year!
I think that is only the electronic shutter.
01-01-2017, 02:16 PM   #12
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QuoteOriginally posted by Cthulhugan Quote
I think that is only the electronic shutter.
Hmm, that's an interesting thought! I have the electronic shutter enabled in Live View, primarily to eliminate shutter camera shake (which is evident with the K-1 at around 1/100 sec to 1/200 sec, especially when using the light 28-105).

Now, I rarely use Live View. It is generally reserved for: waist-level shooting; low level shots; to avoid shutter shake in that 1/100 - 1/200 sec range. However, on NYE I did use it a few times, but can't remember whether this shot was taken in Live View. If it was, than it used the electronic shutter, and that could have caused the "multiple ghosts effect".

I have looked in the exif (using exiftool), but can't see an entry that tells me if I was using Live View or not (or Contrast or Phase Detect AF, which would give it away). Or more directly if the electronic shutter was used. But I could be looking in the wrong place. Does anyone know where to find this information in the K-1 exif?
01-01-2017, 07:58 PM   #13
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Walking speed is not constant. You speed up when you place your foot on the ground and push forward. Then you slow down until you push forward with the other foot.
01-03-2017, 09:43 PM   #14
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Those look like people who were holding still for a brief portion of the exposure, but not the whole thing.
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