Camcorder jerky action, on 1920x1080i

12harry

Distinguished Member
- - - - Note: this is not bad holding of the camera. - - - -



- I'm recording at "best" 1920x1080i - it's at 50fps for UK market. Playing back the files on an LCD TV some unexpected fast action across the screen is recorded in definate jerks (presumably the original frame is "slicing" the action).

I've installed Sony Vegas 10 HD but not yet up to working it....so it is somewhat disapointing to find even the original files are bugged with jerkyness.

1) Is this visual effect normal? ((sure, I should have moved back, reduced the angle etc.)) - but the Van appeared from nowhere!.

2) Is it possible to apply a "cine-like" blurring to these frames, so the eye sees only a smooth rush? It's not many - so a little time spent (on about 15 seconds of footage) would be easy enough... if the facility exists.


I'm told this is part of the problem with digitals - Cine-Film was far nearer like we "see" - so the brain accepted the blurring, provided there were a few sharp bits all was well and good. Modern Digital camcorders and DSLRs frames are just "too sharp".


Also: - I have some well exposed footage of a small march/parade on the other side of the street, it's moving slowly towards me, with tops of cars just cutting into the shots at the frame bottom (I chose a high viewpoint), again these cars are somewhat blocky, being close to the camera...I think this is the same issue....the marching people are perfectly shot (he says).

I'm hoping "maybe" to soften the edges of objects across the frames (er, too quickly), so the eye is fooled into seeing a sharp edge only at the front, with subsequent frames being somewhat less sharp. Now I've seen the effect I may try to lower the shutter speed*, although I like large apertures normally; I may have to compromise. For the March I could apply a frame-bottom blurr-mask to avoid the intrusion, but for the 1st sequence it can't be cut, - that is the subject and I have only one-take available.

Suggestions....pse.


* I don't know if this is possible....far from clear!
 
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PhilipL

Well-known Member
Hi

- - - - Note: this is not bad holding of the camera. - - - -



- I'm recording at "best" 1920x1080i - it's at 50fps for UK market. Playing back the files on an LCD TV some unexpected fast action across the screen is recorded in definate jerks (presumably the original frame is "slicing" the action).

I would guess this is due to the camcorder using a fast shutter speed freezing the action so anything moving very fast would then appear to judder as you see the frozen image for just a few frames flash across the screen, so it doesn't appear like movement. The visual clues our brains need to trick us into realising something is moving very fast is motion blur. This is a trick the film world use having to cope with even slower frame rates, and this is usually achieved by using a fixed shutter speed of around 1/50th second. You would need to set this manually with most camcorders to stop them upping the shutter rate in bright light to control exposure.

2) Is it possible to apply a "cine-like" blurring to these frames, so the eye sees only a smooth rush? It's not many - so a little time spent (on about 15 seconds of footage) would be easy enough... if the facility exists.

You could try any of the blurring type filters, and if you have Vegas, (not available in MovieStudio) then there are motion blur options.

Also: - I have some well exposed footage of a small march/parade on the other side of the street, it's moving slowly towards me, with tops of cars just cutting into the shots at the frame bottom (I chose a high viewpoint), again these cars are somewhat blocky, being close to the camera...I think this is the same issue....the marching people are perfectly shot (he says).

Yes, sounds like bright conditions have caused the camcorder to use a fast shutter speed.

Regards

Phil
 

12harry

Distinguished Member
Thanks PhillipL, (shutter speed), I think this may be the cause. - although being in the right place(=better angle), would help, so often one has to take pot-luck and trust to "experience" - which is somewhat lacking, in my case.
I may buy a ND filter to help in bright sunlight (never thought I'd need one!)

I have a NEX5, not strictly a camcorder; it's a Stills with a "movie" button...1920x1080i
I set the EV down (minus)0.7 which makes the highlights better, although shadows go darker. I know I can fix light-level in Vegas, but am unsure if I can apply it to selected parts of a frame (still learning).
However, the iris and shutter settings are a mystery to me...it shows a "shutter-speed" in Shutter-priority, but as soon as you touch the "Movie button" that disappears...and I suspect it is filming at 50fps which implies a shutter-speed faster than 1/50 - which is quite fast for much motion blur.
I tried a manual lens and this is set by the iris-ring - the camera just exposes by adjusting the ISO I guess - but don't fully understand the "mechanism" - I just wonder if the shutter-speed is fixed - since the number of frames must be, to comply with PAL standard. (All very Confusing).

It's possible I can fix this in Edit ( using motion blur) - but it's other Videographers complaining, not me. However I did notice I need to pan more slowly (using the "fluid-head" tripod), otherwise distant trees get a shimmer effect (like marqee-line)...So I have to be a tad slower.

In Vegas, I know I can "speed-up", so hopefully this won't make the shimmer reappear, but that's for experiment later...One issue I have yet to resolve is to reproduce those faults seen on more-modern "better" screens, when showing our movies which are edited on small PC's/Laptops (which I presume are often even worse?). i.e before I take my Big-Picture to the Video Club.


Thankyou for yr comments.
 
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PhilipL

Well-known Member
However, the iris and shutter settings are a mystery to me...it shows a "shutter-speed" in Shutter-priority, but as soon as you touch the "Movie button" that disappears...and I suspect it is filming at 50fps which implies a shutter-speed faster than 1/50 -

When you press the shutter icon you put the camera in shutter priority mode, the speed of the shutter is shown and can be adjusted. It will stick at this shutter speed now and adjusts the iris as necessary for exposure. To confirm you are in shutter priority mode, touch the screen to see all the settings, and if the shutter speed is shown then that confirms shutter priority mode. The settings disappear after a few seconds to keep the LCD clutter free.

Pressing the iris button will put you in full manual mode for exposure.

It's possible I can fix this in Edit ( using motion blur) - but it's other Videographers complaining, not me. However I did notice I need to pan more slowly (using the "fluid-head" tripod), otherwise distant trees get a shimmer effect (like marqee-line)...So I have to be a tad slower.

The shimmering effect is usually a side effect of too much detail being shown on a screen which requires scaling to fit the whole image to it's resolution, even with full HD resolution TVs scaling may be taking place if overscan is in use. Fine details align up and resize nicely one minute and then the next they fall between the cracks of two different resolutions and resizing doesn't work quite so well, so you end up with a shimmering effect as you pan around anything with fine detail.

Regards

Phil
 

12harry

Distinguished Member
PhillipL, thanks, but I may have confused you...that's how I read it. The shutter-priority display disappears in movie-mode, although the EV continues to show. There is no iris button. (I guess you may refer to the stop-down feature on SLR's to judge the DoF).
When out of movie-mode, the stills-mode is displayed again and I can up/down shutter (or Iris, depending on Priority, Lens, etc.).
In manual-lens (ie a non Sony attached), it displays no Iris, there being no control over the lens, so only shutter + EV.
The Menu for Sony NEX5 is a monument to Confusion. There is an on-line Operation-Manual, but this is pretty much the same as I have, just with colour pictures.

However, this doesn't explain the actual (movie mode) shutter-speed being used and whether it can vary.....I need to conduct some analogue experiments to determine this....

I read in AP recently, that digital cameras can be "incorrect exposure" about 6-stops and still able to be corrected (or regarded as "Correct"), so our thoughts on "Correct" really only apply to a film-camera, due to severe limitation in the silver-process....I guess that's what they meant.
Thanks H.
 
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