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How To Achieve Motion Blur Other Than Timelapse


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#1 Robert Gardner

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Posted 22 May 2012 - 07:55 AM

Hi there,

I was wondering if there is a good way to achieve motion blur with the sort of streaking lights you get at night with a long time exposure. Is there a way how to achieve this sort of effect other than using time lapse?

I will be shooting digital (prob red one). Is there a way i could do it with the camera, or would it be advisable to send out a second unit with a DSLR to get the time lapse sequence?

I am looking to capture a busy intersection with all them car lights leaving them long trails and streaks of light. Everyone has seen it a thousand times, but I never had to film it myself. Any advise is very much appreciated.

Many Thanks,

Rob
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#2 Phil Connolly

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Posted 22 May 2012 - 03:08 PM

The only way to achieve it in camera is due to long exposure times - so the cars move a decent distance while the shutters open. Your best bet would be to use a timelapse feature on a DSLR as I believe you have longer exposure times then the Red. I attempted the effect with an EX1 once and it worked sort of ok - but I couldn't get the exposure time long enough (eg over 1 sec) to really get the smooth blurred lines - the effect was more staccato. Still looked pretty good though.

The effect might be achievable in post with the right effects as things like motion blur can be added - but it rarely looks as convincing as what you can get in camera.
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#3 Phil Rhodes

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Posted 22 May 2012 - 03:18 PM

You can add motion blur in post with a plugin like Reelsmart Motion Blur. I'm not sure how long a blur it'll let you create, if it'll let you go more than a frame, but there are also tricks you can do to stretch things out, render in blur, then put it all back together again and get a similar result. That would probably work.
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#4 Travis Gray

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Posted 22 May 2012 - 03:24 PM

Sounds like it'd all be easier with a photo time-lapse, but I think it'll end up as a different effect than with a video shot with effects added on.

The time-lapse is going to show a passage of time vs. (what I'm thinking of with) video with a longer shutter time, where you'll almost get 1:1 timing, just with blur (or stutter). So I would keep that in mind too.
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#5 Adam Brown

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Posted 22 May 2012 - 06:37 PM

If you set your exposure time to a fixed 1.6 seconds, make sure you set your intervalometer to something like 2 seconds and and try to keep that delay between shutter fire and timer to a minimum. This way, you'll have less of a "shutter lag" and it will appear more as if it were recorded from a video.
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#6 Chris Millar

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Posted 23 May 2012 - 12:24 AM

If I'm reading this right you want streaks of light but not speed up motion ?

If so shoot normally with the largest shutter angle you can get then in post offset many layers of the same footage over each other mixing them so that each layer contributes an equal amount to the resultant frame. The trick is that each layer is offset with respect to the layer below by one frame. You then have to switch on and off each frame um, sheesh - how do I describe this - er, 'accordingly'.

Kind like so:

123456789
123456789
123456789
123456789
123456789
12345...

Notice how the red section is always 3 long but moves by 1 frame only ? that's what we're after Posted Image

This way you accumulate motion blur but maintain natural speed.

Your main variables are:
- The amount of layers, which visually equates to the amount of blur relative to the speed of the motion that caused the movement in the first place.
- The temporal offsets, which visually equates to something you're best left to play with to see.
- The acquisition shutter angle, ideally you want 360deg for this trick

Some cameras have even longer than 360deg shutter angles which is actually exactly what you are asking for ('arbitrarily longer than 360deg shutter angles' to be succinct) - not sure about the red however.

As Phil has led me to investigate into previously 'optical flow' is the kind of carry on that would help here, and there are likely filters, in house comps and plug ins for various composting programs that will do what you're asking already. But if you're keen the brute force technique outlined above can be quite self-fufilling.
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#7 Robert Gardner

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Posted 23 May 2012 - 08:29 AM

Many Thanks guys for the tips. Will have a go with setting the camera to 1-2 seconds exposure and keep it at short burst intervals like 2 sec.
Will also have a go with the method Chris was talking about. The only thing here is I might need endless ;-) layers to create the effect. Sounds like an interesting approach though.

Again, many thanks.

Rob

If I'm reading this right you want streaks of light but not speed up motion ?

If so shoot normally with the largest shutter angle you can get then in post offset many layers of the same footage over each other mixing them so that each layer contributes an equal amount to the resultant frame. The trick is that each layer is offset with respect to the layer below by one frame. You then have to switch on and off each frame um, sheesh - how do I describe this - er, 'accordingly'.

Kind like so:

123456789
123456789
123456789
123456789
123456789
12345...

Notice how the red section is always 3 long but moves by 1 frame only ? that's what we're after Posted Image

This way you accumulate motion blur but maintain natural speed.

Your main variables are:
- The amount of layers, which visually equates to the amount of blur relative to the speed of the motion that caused the movement in the first place.
- The temporal offsets, which visually equates to something you're best left to play with to see.
- The acquisition shutter angle, ideally you want 360deg for this trick

Some cameras have even longer than 360deg shutter angles which is actually exactly what you are asking for ('arbitrarily longer than 360deg shutter angles' to be succinct) - not sure about the red however.

As Phil has led me to investigate into previously 'optical flow' is the kind of carry on that would help here, and there are likely filters, in house comps and plug ins for various composting programs that will do what you're asking already. But if you're keen the brute force technique outlined above can be quite self-fufilling.


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Media Blackout - Custom Cables and AKS

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rebotnix Technologies

The Slider

Glidecam

Abel Cine

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Wooden Camera

Rig Wheels Passport

Ritter Battery

CineTape

Broadcast Solutions Inc

Opal

Paralinx LLC

CineLab

Visual Products

Gamma Ray Digital Inc