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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Stutter in footage?

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Michael Cory

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Im farely new to hd cameras but any and all hd camera footage I view on the web always has a stutter or skipping look when the camera pans. This includes the cheaper cameras and the red one. If I see an hd film in the theater or on dvd i dont see this happening. So i was wondering if this is just the effect of the computer or what exactly is going on. Any explanation would be helpful. I originally thought it was only the cheaper cameras that did this but I see it on the footage posted on reduser.net.

Thank you,
Michael
 
This is caused by the progressive scan nature of film and HD. Unlike interlaced footage, progressive footage has always suffered from this.

The reason you don't see it in feature films is because they know what they are doing. There are very specific rules about the speed of pans at different shutters and frame rates. You break the rules, you stutter.

That's my understanding anyway, I'm not an expert on the subject.
 
Mostly, these come from too fast slow pans with too short a shutter to blur them...
But you cannot really direct the director to avoid it... :)

BUT:
There are some odd cameraspecific stutters... RED has them, too.
@ RedMeet IBC, Ted called it "The cams unsweet spot". :)

You'll particullary see them on high contrast edges, and you'll just have to test, test and test again to see how to avoid them on RED...
 
The cams unsweet spots

The cams unsweet spots

gunleik said:
Mostly, these come from too fast slow pans with too short a shutter to blur them...
But you cannot really direct the director to avoid it... :)

BUT:
There are some odd cameraspecific stutters... RED has them, too.
@ RedMeet IBC, Ted called it "The cams unsweet spot". :)

You'll particullary see them on high contrast edges, and you'll just have to test, test and test again to see how to avoid them on RED...
Click to expand...

On the subject of the "RED unsweet spots", is there a best practice summary that has been derived ? ie: is there a shutter vs focal lens vs usage 'best starting point' (usage is perhaps too loose a term) that can be shared with this community ? We must all be conducting tests and without a doubt being duplicated around the world ...
 
Bastiaan conducted some tests that he presented in the Amsterdam Reduser meet. His conclusion was that the strobing is quite different than the one from film cameras. Film cameras had the old rule that as long as it took at least 3 seconds from something entering the screen til it left it, there would be no strobing. With the Red One this can be different; in Bastiaans tests slow pans were ok, as expected. Fast pans were ok, which was positively surprising. Medium pans were not ok, which was also surprising.

It all depends on your lens, panning speed, shutter angle, fps, and projector. If all of these work against each other, then pans can become an eyesore.
 
Martin Weiss said:
Bastiaan conducted some tests that he presented in the Amsterdam Reduser meet. His conclusion was that the stuttering is quite different than the one from film cameras. Film cameras had the old rule that as long as it took at least 3 seconds from something entering the screen til it left it, there would be no stuttering. With the Red One this can be different; in Bastiaans tests slow pans were ok, as expected. Fast pans were ok, which was positively surprizing. Medium pans were not ok, which was also surprizing.

It all depends on your lens, panning speed, shutter angle, fps, and projector. If all of these work against each other, then pans can become an eyesore.
Click to expand...

would it not be worth 'publishing' these findings (on a sticky RedUser thread) ? i think the community would welcome such information :nerd:
or on one of the Red Wiki's ... as it is hard to find relevant content on RedUser now days ;-(
 
Thanks for the replies. Your guys information has been helpful.
 
Plus i think the better your computer system is, you won't see this shutter effect as much. I have noticed it shows up more on my PC then my APPLE comps:weight_lift: :weight_lift: :weight_lift: .
 
I see this regularly in Hollywood films shot on film and projected on film in theaters, where the camera is being panned at a bad speed for 24P. It's the same on film or HD or Red; pan at certain speeds and you will get it if you are shooting at 24 or 25 frames per second. Shooting progressive doesn't make it worse, it's all about the frame rate. 60i is 60 frame updates per second. 60p is the same only it's updating the whole frame 60 times per second.

There are differences in displaying on film, on interlaced CRT's, on progressive flat-panels. But the fundamental issue is the same for all these mediums.

DP's in the past were much more knowledgeable and strict with panning speeds because of the challenge of shooting in 24P. DP's who "grew up" shooting video at 50i or 60i are having to relearn what was well known in the past. This applies to me as well.

The American Cinematographer Manual has great charts for showing acceptable pan speeds at various focal lengths and frame rates. The charts are for 35mm film, so they are perfect for the Red One. Note that they are for static scenes, so if the camera is following action, such as a car driving laterally or someone walking across the scene, you can pan faster because the eye is on the moving subject and doesn't pay attention to frame shudder. And even for static scenes, panning quickly enough becomes a "swish" and overcomes the problem.

People new to shooting 24P should do their homework, do your testing before actually being on set.

Matthew Verkler
 
Martin Weiss said:
Bastiaan conducted some tests that he presented in the Amsterdam Reduser meet. His conclusion was that the strobing is quite different than the one from film cameras. Film cameras had the old rule that as long as it took at least 3 seconds from something entering the screen til it left it, there would be no strobing. With the Red One this can be different; in Bastiaans tests slow pans were ok, as expected. Fast pans were ok, which was positively surprising. Medium pans were not ok, which was also surprising.

It all depends on your lens, panning speed, shutter angle, fps, and projector. If all of these work against each other, then pans can become an eyesore.
Click to expand...

Was this test displayed with a video projector (as opposed to a film projector)? Certainly there are differences between those, but those differences should affect film-originated footage and Red-originated footage the same. The sharper the footage is, the more strobing should be an issue, and that's where 1/3", 1/2", and 2/3" sensors might have more problems because much more of the screen is in focus compared to 35mm film and Red. At this test, was film-originated footage shown along with Red footage?

Medium pans are the most problematic for film, Red, anything at 24P, and therefore NOT surprising. Fast pans are okay because at a given shutter speed, motion blur negates strobing. And having a moving subject in the frame that the eye is following allows for medium overall pan speeds that won't bother the viewer. If the viewer is watching the background instead of the subject in this example, then they will notice the strobing.

Shutter speeds are of course important; faster shutter speeds greatly compound the problem. My old wind-up Bolex, for example, has a 115 degree shutter and strobes much more than my BL2 with a 180 shutter. Luckily, Red can have whatever shutter speed we want.

Film projectors show each frame twice to reach the human eye's threshold of persistence of vision; video projectors have various "refresh" rates and there can be real differences there. But not so with the method of origination, whether Red or 35mm.

Matthew Verkler
 
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