Motion Blur

[Engin Torker]

Hi,

 

I couldn't find a more pronounced example of this so I hope you'll have the luck to find the scene I'm talking about.

About 1.30 minutes into the Pilot episode of Sons of Anarchy there are these guys loading crates to the truck.

I see a very pronounced motion blur on this scene.

For those who don't have the chance to see that scene, it happens a lot especially with the contrasty night scenes. Vertical contours on people from the kickers / street lamps come forward in front of the dark surroundings and when they move, you have this very blurry / videoish look.

I know this motion "artifact" is more pronounced on Panavision Genesis which I assume is used on that scene but I also keep seeing this on other cameras including Alexa. The thing is, especially for Alexa, sometimes this is more pronounced and sometimes I don't see it at all, in the scenes of identical lighting on different projects.

What creates the difference? How can we avoid it?

Thank you

[Phil Rhodes]

Can you link us to an image demonstrating the effect you're talking about?

[Engin Torker]

I hope that's ok to share this here.

 

Please see the night ext. scene starting at 1.30, especially the fast movements:

 

http://www.dizist.com/izle/sons-of-anarchy-1-sezon-1-bolum/

[Anthony Schilling]

I can't see the clip to know exactly what you describe, but motion blur is directly related to the exposure time of each frame. Longer exposure times will have more motion blur, shorter exposure times will have a more staccato motion with sharper images.

[John E Clark]

I haven't seen the clip as yet, but 2 ideas do occur. 1) If the shot is a 'nigh/dark' scene, then perhaps setting the shutter to 270 deg, or as 'long as possible', to get a bit more exposure, could give rise to more motion blur. 2) This also could be a 'creative' decision as well... regardless of the exposure consideration.

[George Ebersole]

I just streamed it in hidef (720p) from Amazon. Nothing lept out at me. There's a tiny bit as the biker in the tail gate takes a box and puts it behind some other boxes. Maybe it appears more severe on a big screen TV?

[Jeff L'Heureux]

I see what you're talking about. It's subtle for those who don't know what to look for but it is definitely one of the telltale signs of a digital camera vs. a film camera. It seems to happen on night scenes where digital cameras are used, and yes I've even seen it on Alexa footage. Off the top of my head I know I noticed it in the night scenes of "Ted", shot on the Alexa, and in a few shots of the dark interior action sequence of "Oblivion" with the drones attacking the people, shot on the Sony F65. What confuses me about the latter in particular is that the F65 has a rotary shutter, which one would assume would mimic the exact motion blur as a film camera, but there are clearly a few shots in Oblivion that have that 'video-ish' motion blur. The most awful example of bad digital motion blur I saw was the end hand-to-hand fight in "Gangster Squad". It was so bad in fact that the person I went to see the movie with, who is not a film buff of any kind actually whispered to me "why does this scene look like weird video footage?" There have been threads about this bad motion blur on Gangster Squad's IMDB forums as well, so it's really noticeable.

 

What I don't know is if this is happening intentionally by the DP's, or a side effect of these camera sensors working in low light, and why it appears in some shots but not others in any given movie shot on digital.

[George Ebersole]

Can you post a link of an obvious example for idiots like me?

[cole t parzenn]

How is video blur different from film blur?

[Engin Torker]

Ok, so I will try to define it better.

 

First of all I'm not talking about a shutter related motion blur.

 

I've always thought that this resembles the look of an old tube camera with its ghosting trails. You can see that look to its extreme in Daft Punk's Robot Rock video.

 

For video, I started to think that this is a codec related issue. But I really don't know the ins and outs of firmware stuff so please forgive my ignorance.

 

Here's the first example:

 

 

 

This is from the first episode of the TV series "Legends" (2014). Since this is a much brighter scene you can see what's going on around.

 

You can see the vertical repeated lines and if you look at it in motion its a really fast pan, so these lines are not from multiple frames but some kind of interpolation (if that's the right term) between fewer frames by the codec.

 

This shot had exactly the look I'm talking about and I've seen many other fast pans on other digital cameras in similar environments that didn't have this effect.

 

 

Here's a screen shot from the scene which I've mentioned earlier, from Sons of Anarchy:

 

You can easily think that this is a regular motion blur. But when you look closely to the guy's nose, I think there's also a duplication of frames.

 

I hope I could show what I mean. I'm also very curious that how this thing didn't become a "video issue" and get a name, like rolling shutter. Or what is it, if it did?

 

Thank you

[John E Clark]

Ok, so I will try to define it better.

 

First of all I'm not talking about a shutter related motion blur.

 

If the Genesis camera was used, then the 'ghosting' could be due to an artifact of the CCD sensor. Depending on the conditions, CCDs imagers would have sort of a vertical 'flare' due to how the sensors were constructed, and how the 'data' was read out.

 

Here's a thread from Paul Mailbaum ASC, who apparently was the DoP for the series, but apparently not for the Pilot. The thread indicates a Genesis camera was used.

 

http://www.cinematography.com/index.php?showtopic=31242

[George Ebersole]

I see a form of motion blur all the time with regular features in theatres. As the camera pans with a character the background doubles up, and I've always found it very distracting.

[Engin Torker]

Yes, the Genesis has it most of the time.

 

But I see it time to time also with CMOS sensor cameras like Alexa.

 

I still wonder how it can really be avoided, which seems to be possible considering we see many shots without this effect?

[John E Clark]

Yes, the Genesis has it most of the time.

 

But I see it time to time also with CMOS sensor cameras like Alexa.

 

I still wonder how it can really be avoided, which seems to be possible considering we see many shots without this effect?

 

I usually don't pixel peep while watching a presentation in a theater. These days I wait for the bluray, and even then unless I'm looking for some specific reason, camera work, editing, etc. I don't pixel peep much.

 

My general thought is all image capture methods have limitations, and perhaps the 'bloom/streaking' of the sensors, whatever the technology, is 'just the way it is', and that would give rise to recommended use limits. I've not seen a recent copy of the American Cinematographer Manual, to see if it has been updated with digital capture recommendations.

[Phil Rhodes]

The segmented motion blur shown above is generally caused by lighting that isn't entirely flicker-free. Often things like fluorescent tubes (including compact fluorescents), metal halide lights and LEDs that are not intended for film and TV work have flicker at two or four.times the mains frequency due to various stages of rectification and power conditioning. It looks like about four flickers per frame in your example, which lends credibility to this interpretation. Any camera system, film or video, can exhibit this problem.

 

Otherwise, the issues around CCDs and vertical flare are very real but don't have much relevance to motion blur. F35 and the related Genesis were particularly bad offenders in this regard, and I was never impressed with either. Current CCDs are much better, but even broadcast cameras are now starting to use CMOS sensors in any case.

 

The way in which film and video cameras render moving subjects with blur is very subtly different, due to the way in which a rotating shutter exist in an out-of-focus plane and gradually occludes light from the frame as it rotates. However, these differences are only really visible under laboratory conditions, and differences observed in real-world applications are more likely to have been caused by other, unrelated obscuring issues.

 

All the best,

 

Phil

[Gregg MacPherson]

....The way in which film and video cameras render moving subjects with blur is very subtly different, due to the way in which a rotating shutter exist in an out-of-focus plane and gradually occludes light from the frame as it rotates. ....

 

 

I was going to point out that some of the film cameras do have shutters that are considered focal plane shutters, but while writing I wondered if you are saying that the shutter will be out of focus, even the "focal plane shutter(s)".