Re: [CinePaint] Looking for a feature useful to smooth timelapse sequences - grading

On 11/21/06, Kai-Uwe Behrmann <[email protected]> wrote:
> CinePaint has the curve tool, which works in RGB and Lab colour spaces.
> The curve tool is quite common. So I wonder if you had allready tried
> this. It is a per frame editing tool.

Yes, I'm familiar with curves.  Problem is, you can't manually tweak
the curves of 3,000+ frames.  It needs to be automated.

> One difficulty I see with changing punctually the light conditions is
> that it will introduce so many changes that it is hard to follow up.
> Probably you can use the flash in the whole film. This way its influence
> is allways present. Telling us more about the special conditions would
> help us understanding the problem you are faced with?

For example, I used to work on the 32nd floor of a building in
downtown Portland.  I would shoot timelapse sequences out the windows.
 Clouds.  The river.  The cars on the streets.  The lights coming on
at night.  Sunset.  Lots of stuff.  All using existing available
light.  Flash wouldn't be of any help.  And it certainly wouldn't help
me fix the sequences that I already took.

> For colour editing of film sequences, it is called color grading in the
> film industry, there was not that much interesst in the past, order wise.
> This is probably because grading in film studios is most often hardware
> based, with trottles, turning knobs and balls. A colorist tould me it is
> like playing piano - in real time. ... quite hard to acieve with keybord
> and mouse.

Naturally, I couldn't babysit the camera all day, because I was
working.  So I used automatic exposure.  But as the light conditions
changed, the exposure changed.  This produced sometimes very sudden
changes in the visual appearance of individual frames, which if the
conditions hovered near the boundary between one exposure setting and
another, the resultant video sequence was often full of what looked
like flashes of light.

I once wrote a script that took a timelapse sequence and calculated
the 'average' of some number of frames before and after each frame.
So I took the 15 frames before and the 15 frames after, or about one
second of video time, and took all 31 images and produced an 'average'
image.  I then used that as the frame for that moment.  Naturally, I
did the same thing with every single frame.  The end result was
amazingly smooth.  It was exactly what I wanted, as far as light
conditions goes.  The flashes of light were completely gone.  But cars
in motion were completely removed from the image, too!  The lighting
was perfect, but the action was missing!

What I need is to automate the task of taking the actual frame and
tweaking it so that its overall appearence most closely matches that
average image.  It's just math, right?  It has to be possible!  If I
can find a way, then the end result would be as smooth as the average
image as far as overall lighting goes, but with all the details of the
individual frames intact.

> Anyway CinePaint has a feature called look profiles to change colour
> appearance statical for a whole sequence. It is a bit slow due to the
> underlying CMM. But it could be modified to manipulate continious changes.
> The manipulation would be done in the look profiles - the abtract style of
> ICC profiles.

This might hold some promise.  But how would one create the look
profiles so as to cause the individual frame to most closely match the
target appearance?

What I had originally tried was doing gamma adjustment.  And that
seemed to get me closer.  But I need to do level adjustment, as well,
at the very least.  Curves adjustment most likely is needed, too.  But
I'm very new to the mathematics of image adjustment, so I know
virtually nothing about what it takes.  Anyone here have any ideas, or
can point me in the right direction?

Thanks again!
-- 
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John Arrowwood
John (at) Arrowwood Photography (dot) com

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