Making a Drive/Time-Lapse video with motion blur

[Phil]

Hello everyone,

To cut a long story short, I am planing to do a road trip in the upcoming weeks of a long(er) road trip. The original idea was to use one of my GoPro Hero 3 cameras to take interval shots and then merge them to a video file later.

I have about 4 64GB sdcards, so memory shouldn't be an issue when setting the camera to shoot 7MP pictures (4-6MB in size). One of the drives will cover around 300km and take 4 hours. During this time, the camera will be plugged in to an external power supply so that won't be an issue either.

So the GoPro offers these interval modes:

0.5s / 1s / 2s / 5s

Originally, I planed to use 2s, but now doing some research, I figured that when driving you want the shortest interval available. Even so, taking a photo every 0.5 will still result in a relatively "choppy / jerky" video as these pictures will be taken with a relatively short exposure time, resulting in sharp photos without any blur.

Here's an example:



To make the video footage more appealing and smooth however, you do want to have blur. There is something called the 180° rule (or 180° shutter angle) which basically means that for a 24fps video, you'd want to have each photo within a 1 second interval exposed at 1/48th of a second. This gives you just the right amount of blur that we usually get to see in cinematic films etc and looks natural and pleasing.

Example:


The problem is, using a GoPro camera, I do not have control over the shutter speed.

So, any ideas how I can get it done using a GoPro camera? The easiest method would be probably to buy an ND filter for the GoPro Hero 3 (not sure I can get one on such short notice, given the GoPro Hero 3 isn't the most recent camera), but that would only induce longer exposures, not necessarily the right amount of exposure for the 180° rule. But perhaps any longer exposure would be better than no blur at all?

The other techniques I am looking into are to set my GoPro Hero 3 to video recording at 4k resolution at 15fps. This will give me roughly of 3 hour footage using a single 64GB card. I could then speed up the video in post to get the "timelapse video" in the duration I want it. This may yield a smoother result, than taking individual photos.

Alternatively, I could go with the 0.5s per picture interval and use some fancy image blending to create some blur in post. The problem is, I can't seem to figure out if this is possible and what it would look like. Blending perfectly sharp and still images would not create motion blur but just blur...

So, any ideas? Anyone try something like this? Or any technical minded input on how to achieve the desired result?

The problem is, by next week I'll be on that road trip and by then, I need a good idea on what route I'll be going with. Either I'll be filming in 4k at 15fps or I'll be taking thousands of pictures without knowing yet what might yield the best result...

[Greg Locock]

I assume you don't want to buy Adobe Premiere pro? You can get a free trial, it does motion blur.

You could probably do it for free in octave, basically read avi file, split it into frames. For each consecutive pair of frames work out the displacement of features across the frame, then apply that displacement to all of the first frame.

Sounds like it'll take a while.

[Andres125sx]

Personally I don´t like motion blur. People usually say that´s the natural feeling, but to me the natural feeling is what we see with our eyes, and we don´t see any motion blur with our eyes

This motion blur paranoia (sorry but I´m drone operator and I´m sick of hearing about motion blur) IMHO comes from past eras where cameras were not able to record a sharp video. Since we humans are creatures of habit and don´t accept changes too well, we´ve been watching motion blur on cinema and tv for decades, so now that cameras can record a sharp video no matter how fast is moving the target, people find it weird. I find it amazing.

I´ve worked with producers who don´t like Laser Ultra (4k 60fps). Personally my reaction was...


But anything related to images is subjective, so you´ll have to make your own decision. I´d take pictures (filming 4k for a time lapse is crazy, you´ll get several GB for only some seconds video), make a sharp video, and if you don´t like the result you can always add some motion blur afterwards

[Phil]

I assume you don't want to buy Adobe Premiere pro? You can get a free trial, it does motion blur.

You could probably do it for free in octave, basically read avi file, split it into frames. For each consecutive pair of frames work out the displacement of features across the frame, then apply that displacement to all of the first frame.

Sounds like it'll take a while.

Thanks Greg!

I actually have an (old) copy of Adobe Premiere somewhere... but I never really got into movie editing (I'm the born photographer), so I've never used it. The motion blur feature sounds interesting.

I did a small test last night (and will again today) where I took pictures at 0.5 seconds interval. Tried adding them using GoPros Studio software (ugh, didn't really get far with it and it looks like you can only use that software to upload directly to youtube or facebook...) and also tried iMovie. iMovie can do a lot, but I don't think it's the software to use to blend thousands of pictures into a movie. I was able to speed up my 4k@15fps video quite easily by a factor of 10 quite easily though.

In case my version of Adobe Premiere is too old (or I can't find it), any other suggestions as to what software is outthere?

[Phil]

Personally I don´t like motion blur. People usually say that´s the natural feeling, but to me the natural feeling is what we see with our eyes, and we don´t see any motion blur with our eyes

Motion blur is a simple necessity of framerate. If you have a limited framerate, you have a choice to either blur the frames by a longer exposure to convey the motion or you end up with a razor sharp frames that will then look like a fast slideshow when watched in succession.

An example:
If I take a picture of a helicopter with a shutter speed of 1/4000 of a sec, the rotor blade will be razor sharp and frozen in its movement. The resulting picture will look like the helicopter is hanging mid air. Example
The same reasoning can be applied to F1 photography. Use too fast shutter speeds when photographing F1 cars at 200kmh and they too will be frozen and look like a parked car instead of a moving one.

To convey motion better in a still frame, ideally you want a slower shutter speed of say 1/250 or less (depending on focal length and subject). The resulting image will convey the motion of how far the rotors travel within that time.

The problem now is that the GoPro Cameras have a fixed aperture (of f/2.8 ), so the only way the camera can manage a correct exposure is by using ISO and shutter-speed. In broad daylight, the camera will use a ridiculous fast exposure to limit the amount of light to the sensor. This will result in razor sharp frames that convey no motion at all. If you film at 60fps and watch it in realtime, this is less of a problem, but given I intend to make a time-lapse movie from frames every half a second, the motion will be choppy, even if I speed up the movie to whatever framerate you want.

It will look like the first movie I linked where there will be too much information for the viewer to watch, where the bottom half of the picture changes completely with every frame. It would be more pleasing to have some motion blur to convey the movement. As I intend to use 30fps as framerate and I want my 300km journey to be conveyed in 4 minutes, you can do the math:

300km * 1000 = 300'000m distance.
4 minute video at 30fps = 7200 frames.

300'000m / 7200 frames = 41.6m per frame or 1.25km per second (30 frames).

As you see, every frame should convey the movement of 41.6 meters, but won't if the images will be razor sharp due to ultra fast exposure times. It'll be literally a snap shot of whatever the camera captured at that specific moment. Per second, that would equal 1.25km. Do that without any blurring and well, it will look choppy, like a fast slideshow.

So in order to "smooth" out the footage, the only way to get the GoPro to do longer exposure times is to use an ND filter and reduce the light to the sensor. Or indeed by adding some kind of fancy blending or motion blur in post...

[Andres125sx]

Still pictures are a whole different world. In that case I agree motion blur is necessary, as that´s the only way the viewer can notice the movement. But with video it´s different, you don´t need any blur to notice what´s moving and what´s still, as it will be moving or still

But I agree maybe with a time lapse it may be different. Any reason to use 30fps? With 60 it will be one frame each 20m, and that looks pretty reasonable


BTW, if you want a ND filter but don´t have the time to order, you can always use some old/broken sunglasses, that´s a ND filter after all

[Phil]

I suppose I am running fear of hijacking my own topic, but just to clarify this...

I think the whole topic about ND filters and action-cameras (which also includes most drones) is because these cameras (like the GoPro) have fixed apertures, hence they regulate correct exposure only through the shutter speed. If you are filming at a very high framerate (like 60fps), this may not be such a big problem, but it can still cause rather jittery looking footage. The jittery footage becomes more apparent with a lower framerate. So if you were to film at 30fps, the footage would definitely look more "jumpy" because the camera can only regulate a correct exposure by using faster shutter speeds (...that freeze the frame). Using ND filters to increase the exposure time of these cameras is an easy and cheap way to get some motion induced blur and achieve smoother footage (also more cinematic footage).

Think of it this way: If you had a half decent camera in your drone that had a variable aperture, your camera footage would be doing all that by itself by finding a good mix between aperture and shutter speed. In brighter conditions, instead of simply shortening the exposure time, your camera would close the aperture to let in less light. Action-cameras like the GoPro and most Drones don't have this ability - their aperture is fixed and always wide open (meaning maximum amount of light goes in, irregardless if its bright or dark). ND Filters therefore have an appeal because it lets you limit the light that gets captured by the image-sensor and keep shutter-speeds in a more normal range.

I would think for a drone, fast panning / rotating at especially 30fps highlights nicely why you want some blur. If you don't use any filters, the movement of the panning (depending on how fast you do it) will look quite edgy / jittery The effect would become more pronounced on an extremely bright day, less on a cloudy day. Of course, you can just use a higher framerate (60fps), but then you're only halving that effect, not necessarily getting rid of it. So under extremely bright conditions, a ND filter might be recommendable (even for you).

As for your question why not do timelapse at 60fps?

Simple: It'd be overkill. The aim is not to convey speed, but to convey the scope of a longer journey in a shorter amount of time. The road-side detail is the least interesting about this footage, the focus should be on the surroundings further away. Doing it at 60fps therefore would be a waste of data.

Contrary to wasting memory though - the reason for capturing 7MP images is to have the best possible starting point. To create a timelapse, I could either go 4k, or downscale to 1080. And if I wanted to go back and grab a specific image of the journey, I'd have it in the best possible resolution. Same if I decide to go the filming route and filming at 4k @ 15fps. This way I have more data that might be valuable in post-processing later.

[dans79]

In case my version of Adobe Premiere is too old (or I can't find it), any other suggestions as to what software is outthere?

I use the studio version of DaVinci Resolve, but the free version is pretty powerful if you have the computer to run it.

https://www.blackmagicdesign.com/produc ... ciresolve/

[strad]

I use pinnacle .. works fine but what I don't understand why you're not just shooting video.
I have done quite a few trips from cars with my GoPro.

[Phil]

Thanks dans and strad, I'll be checking both programs out!

@Strad
You're right. Filming might just be easier, I guess. As in film 4k@15fps and then simply speed up. The original thought was to use the interval timer because I'd end up more efficient with a higher quality video and because of... well, speeding up a video feels a bit like cheating vs doing it like a time-lapse is more... real? Sorry, that's the elitist/perfectionist in me speaking.

Other food for thought is: on my GoPro Hero 3 using a 64 GB sdcard I get the following:
1080p@60 - 4h30m
1080p@30 - 7h00m
1080p@24 - 4h30m
4k@15 - 3h00m
2.7k@24 - 3h00m

If I do 0.5s interval shooting, I think I'll fill my sdcard in about 2 hours of driving... so perhaps it would be more efficient to film instead.

n00b question inbound... When I film, my GoPro always splits up the movie files to aprox 4GB files due to the Fat32 filesize limit. Is it possible to combine these parts into one seamless file again?

[dans79]

what I don't understand why you're not just shooting video.

I think he has done the math and determined he would run out of space.

[Andres125sx]

I suppose I am running fear of hijacking my own topic, but just to clarify this...

I think the whole topic about ND filters and action-cameras (which also includes most drones) is because these cameras (like the GoPro) have fixed apertures, hence they regulate correct exposure only through the shutter speed.

No, ND filters are used even with 15kg Cinema cameras, they´re used for several purposes, from producing some blur even when the light conditions are excelent, to simply keep your aperture at the optimum for your lens

Think of it this way: If you had a half decent camera in your drone that had a variable aperture, your camera footage would be doing all that by itself by finding a good mix between aperture and shutter speed. In brighter conditions, instead of simply shortening the exposure time, your camera would close the aperture to let in less light. Action-cameras like the GoPro and most Drones don't have this ability - their aperture is fixed and always wide open (meaning maximum amount of light goes in, irregardless if its bright or dark). ND Filters therefore have an appeal because it lets you limit the light that gets captured by the image-sensor and keep shutter-speeds in a more normal range.

Sorry Phil but, are you really explaining how a camera works to someone who work with cameras for a living?

And no, auto modes are for amateurs, anyone working with cameras proffesionally adjust everything manually. Myabe you were assuming I work with a phantom, but that´s not the case

BTW, the 180 rule is not for motion blur, but to avoid rolling shutter/jello effects and also to get a feeling similar to past eras cameras as those cameras used a 180º shutter, but motion blur don´t have any rule of thumb, as it will depend on the movement speed in your frame. It´s not the same creating some blur if you´re cycling for example or if you´re filming a racing car, shutter speeds must be completely different in each scenario, so no rule of thumb can solve both, you need experience

I would think for a drone, fast panning / rotating at especially 30fps highlights nicely why you want some blur. If you don't use any filters, the movement of the panning (depending on how fast you do it) will look quite edgy / jittery The effect would become more pronounced on an extremely bright day, less on a cloudy day. Of course, you can just use a higher framerate (60fps), but then you're only halving that effect, not necessarily getting rid of it. So under extremely bright conditions, a ND filter might be recommendable (even for you).

Yes and no. Yes, ND filters might be recommendable even for me, and even for Hollywood studios, as I explained earlier. But no, fast panning don´t need any blur, actually any blur while panning is considered a poor shot, as it´s not creating any movement feeling, just blurring the whole frame.

Anycase I´m not sure about the reason you keep insisting on ND filters I think you took my recommendation about using the glass of an old sunglasses as a joke, but I was dead serious, if you want an ND filter but can´t find it for your camera, a sunglass is exactly that, a dark glass built for optics so no deformation, no odd effects, it´s just a not calibrated ND filter

As for your question why not do timelapse at 60fps?

Simple: It'd be overkill. The aim is not to convey speed, but to convey the scope of a longer journey in a shorter amount of time. The road-side detail is the least interesting about this footage, the focus should be on the surroundings further away. Doing it at 60fps therefore would be a waste of data.

It´s not a matter of road-side detail, but jerkiness. If each frame jumps 40m it may lack flow, if each frame jumps 20m it may not

Contrary to wasting memory though - the reason for capturing 7MP images is to have the best possible starting point. To create a timelapse, I could either go 4k, or downscale to 1080. And if I wanted to go back and grab a specific image of the journey, I'd have it in the best possible resolution. Same if I decide to go the filming route and filming at 4k @ 15fps. This way I have more data that might be valuable in post-processing later.

Ok but if you want to save memory, avoid full resolution pictures. If you´re not going to play with zoom in post, and you won´t need any stabilization, recording still pictures quality is completely overkilled. I´d rather take fhd pictures to compose a 60fps video, to taking 4k pictures to compose a 30fps video, it´d save lots of memory and the video will flow better. At least for a driving timelapse.

[Phil]

Sorry Phil but, are you really explaining how a camera works to someone who work with cameras for a living?

Sorry, but reading your rant about ND filters ("motion blur paranoia" as you put it) did come across as very basic understanding on your part. If you know what you want/like and how to get it to your preference, no offense intended and none taken.

As for the sunglasses - sadly this won't work, as a sunglasses will not cut back the light nearly enough by the amount that I'll be needing it and I want to avoid aberrations that I can't correct later on.

[Phil]

Anyway,
I did some extensive testing the last two days and these are my findings so far:

#1 - Filming (daylight/nighttime) / iMovie speedup (10x and 20x)
I did two tests. Once at night and one during daylight. In darkness, the camera boasts relatively high ISO (most likely boosted) as there is a lot of grain and noise present. In post I used iMovie since that was the only program I had available on short notice and did a simple speed-up of the footage. Both daylight and nighttime footage is relatively jerky even at 30fps. I don't know how iMovie merges the data, but judging by the relatively short rendering time, I assume that frames are skipped to do the speedup. No blur/frame blending is done. As recommended in this topic, a better more sophisticated software like Premiere or others will probably yield better more fluid results.

#2 - 0.5s Interval shooting (nighttime) / merged with Interval on OSX
I did two tests as well - once with ProTune enabled and once without. First test was with ProTune enabled and for some reason, this leads to shorter exposure time even in night time. Analyzing the EXIF data, I noticed shutter speeds consistently at 1/5.5s (0.188s). With ProTune turned off, the shutter speeds dropped to 1/3.3s (0.3s) which is almost a stop slower. Merging both sessions into a video with the application "Interval" (freeware) on OSX produced quite nice results with nice fluid/smooth blurring that conveys the motion well.

For the record - a 30 minute drive yields around 2.5 minute of footage and 3600 images.

#3 - 0.5s Interval shooting (daytime) / merged with Interval on OSX
Same road, but shot at daylight. Currently, it's rather cloudy with blue skies in between and according to the EXIF data, the GoPro exposes the image at 1/400s (0.0025s). Driving at 80-100km/h and this yields an expected razor sharp image. The resulting export with Interval confirms this, with a rather jerky/choppy motion.


Conclusions so far...
I like the idea of doing interval shooting. Yes, video mode might be easier and in the end convinient, it'll allow me to go back to watch my entire (most likely boring) drive and probably despite all earlier considerations... be more memory efficient too. Despite all that, I think I'll be doing interval shooting. It just seems... more stylish and allows me to be a bit more creative in post-production without having to use software like Premiere / After-Effects and others that cost an arm and a leg.

Now, the daytime footage I have taken so far does expose the earlier concerns of very choppy footage. To counter act these and end up with proper exposed images (for the 0.5s interval), I have ordered a 58mm filter adapter for my GoPro camera which should hopefully arrive in time, together with an ND32 and a ND1000 filter (I already have a ND8).

ND8 = 3 stops darker
ND32 = 5 stops darker
ND1000 = 10 stops darker

I have also asked a friend to supply me with an image he took with a GoPro camera during summer in broad daylight. The EXIF data suggests that during extremely bright conditions, the GoPro will expose at shutter speeds up to (or more than) 1/4000s (0.00025s). Assuming I'll have a similar brightness level in Australia, a 10-stop ND filter will reduce the exposure by 2^10. Which translates to roughly to 1/4000s without ND filter to 1/4s (0.256s) with an ND1000. If I encounter cloudy weather on my drive (like in my test), I could use the ND32 (5 stops) or stack it with my ND8 to get a combined 8 stop. I think to produce the "look and feel" I am aiming for, the images should be exposed around 1/4s (around the night time results in test #2 above) during daylight.

Might add some Youtube clips later on if interested to highlight these results...

[dans79]

@Phil, if you want some nice Filters check out B+W. They are excellent filters, but pricey.
https://www.schneideroptics.com/Ecommer ... spx?CID=57

n00b question inbound... When I film, my GoPro always splits up the movie files to aprox 4GB files due to the Fat32 filesize limit. Is it possible to combine these parts into one seamless file again?

Most editors will easily do that. ffmpeg will also do it. If you're comfortable working in a command prompt give it a try, it's powerful and flexible, but has a steep learning curve.
https://www.ffmpeg.org/