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24P Judder

Gonzo_Entertainment

Gonzo_Entertainment

This was posted elsewhere on the web, thought I'd repost here.

Making me consider shooting 29.97. I have already decided to on future TV commercial projects anyway to avoid having to do the pull down in post, but almost making me consider doing it on narrative stufff. With the 5D sensor I think it would handle it pretty well without losing much "cinema" feel. Especially if it's web content.


http://www.hdvideopro.com/technique/miscellaneous-technique/help-desk-did-i-judder.html?start=1
 
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interesting explanation of the issue.. its a perfect problem for software to solve.

"The dimming effect of a mechanical shutter allows for accurate recording of anything moving at 12 Hz or slower, and it adds enough blur to anything moving faster, so it appears natural to our eyes. With the hard cutoff on a digital shutter, anything moving faster than 12 Hz starts to create temporal aliasing in the form of jumpiness. The mechanical shutter gives the perfect mix of sharpness and blur. "

create a plugin that blurs any frame to frame movement over 12hz.. how hard can it be.. (lol, thats a joke)


EDIT: The rest of this post is not related to the article, they are talking about a DIFFERNT problem that I am.. the ABOVE call for a software fix is still valid..

Actually, I don't buy the explanation. Plenty of 24p FILM looks jumpy when panned too fast etc. I DO think there is something going on.. but its more a bandwidth \ compression \ AVHCD P and I frames problem...

My hacked GH2 looks 10X time better with camera motion then it did before the hack..
 
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If you look at some of the stills from the site, in the light coming through trees in the background, you can see where the "shutter" opens and closes. The end of the frame is a hard vertical line in at the tail end of the motion blur. In the "analog" one, the hard lines are gone. Due to the digital nature of the medium, any motion that blurs in the background at any frame rate will do exactly this same thing.

I've know for a while that it wasn't the frame rate specifically making digital footage look digital, thought it was the shutter speed of 1/60 rather than 1/48 -- but this is the part that was eluding me. The variability of the light at the opening and ending of the frame's exposure. AWESOME! I was kinda right in my dissatisfaction with the 30p vs. 24p explanation for the "film look" VINDICATED!!!
 
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I'm a pretty intelligent guy. I have a background in science and math. And I swear, for the life of me, I understood NONE of that. I even watched the video on their website. WTF? This is making me feel dumb. :blush:
 
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Cracker Funk said:
I'm a pretty intelligent guy. I have a background in science and math. And I swear, for the life of me, I understood NONE of that. I even watched the video on their website. WTF? This is making me feel dumb. :blush:
Click to expand...

It's pretty cryptic camera nerd stuff for sure. I understand just enough to be dangerous. I have become a camera semi-nerd just so I can help my "I kind of know digital, but I spent most of my career on a panaflex" DP. He's the best operator I have ever seen and a good DP, but I help guide him on playing to the strengths and avoiding the weaknesses of my particular camera.
 
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As the edge of an opening rotating shutter moves past the negative, it unveils the light to the frame... as it rotates, it doesn't fully allow light to pass at the beginning of the exposure, nor at the end.

If something is moving across part of the frame during that time, the start of the short period in time is not fully exposed until the shutter has turned enough to allow all of the light to the frame, and it tails off again at the end. So with a mechanical shutter, we end up with a gradient leading into and out of the main exposure time of the frame.

In digital, there is no partial exposure, it's full exposure at the head and tail of each frame (on and off) - so things moving through frame that would normally show up with a motion blur don't have the partial exposure gradients at the head and tail of the streak like the mechanical shutter would.

So, as the object travels across the frame, it blurs, this blur has a different aspect which looks a bit like this:

. o 0 O 0 o . - Mechanical motion blur
O O O O O O - Digital motion blur
 
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