Similar topic...
FWIW You can also use a similar technique to remove camera dirt etc, which is
behind the sensorClean tool (after a similar discussion a few years ago)
http://www.nukepedia.com/gizmos/gizmo-downloads/filter/sensorclean/
In this case you have a dirty held frame, a cleaned version of the same held
frame and the image to clean.
It divides the dirty and clean reference frames which is the case of sensor
dirt, gives a white frame with a superbright spot where the dirt was. the
result is then multiplied on the image to clean, and removes the dirt spots,
depending on how well you painted the clean reference. Not for all shots but
works on most (90% I'd say).
Howard
>________________________________
> From: Fredrik Pihl <fre...@gmail.com>
>To: Nuke user discussion <nuke-users@support.thefoundry.co.uk>
>Sent: Sunday, 13 May 2012, 22:37
>Subject: Re: Re: [Nuke-users] Analyze Brightness in a Region of Pixels to
>drive Grade Node
>
>
>lovely tip by mr Rowell :)
>
>
>On Sun, May 13, 2012 at 9:57 PM, Paul Schoen <dottore.pa...@gmail.com> wrote:
>
>Hey,
>>
>>thanks for the useful input using the curve tool as well as the "blurring the
>>rectangle"-trick. I messed around with the curve tool with something like
>>this "CurveTool1.intensitydata.r/CurveTool1.intensitydata.r(start_frame)(in
>>my case 1)" and put in the gain of the grade node.
>>
>>But because the shadows are wandering and do not darken the picture
>>uniformally, I had no luck with that. So I tried the tip by James Rowell
>>which works absolutely magnificent because you can adjust the crop according
>>to the area to be covered and minor local changes are reflected as well
>>depending on the strength of the blur applied to the crop. You can even mix
>>different area with aligning several crops together I found out.
>>
>>Of course it still needed fine tuning because shadows do not only darken
>>certain areas but also make them more blue (=cooler)...
>>
>>Thanks a lot!
>>
>>Paul, Vienna
>>
>>
>>
>>
>>2012/5/12 Eetu Martola <e...@undo.fi>
>>
>>
>>>________________________________
>>>
>>>From : James Rowell
>>>>Subject : Re: [Nuke-users] Analyze Brightness in a Region of Pixels to
>>>>drive Grade Node
>>>>
>>>>
>>>>Hi Paul,
>>>>
>>>>
>>>>There may be a tool that already does what I'm about to describe, but I've
>>>>done something like what (I think) you want in the past by cropping to the
>>>>small area that you want to analyse then put a sufficient blur on that
>>>>small area to smooth it all out, then reformat the small crop up to a full
>>>>size image. Then, take a "frameHold" on that image on some reference
>>>>frame, then divide the one by the other and you now have a full frame image
>>>>that you can use to multiply against anything else to CC it in a way that
>>>>will mimic the frame by frame difference of your little sampled area over
>>>>the course of the shot, so you can (for example) reproduce flickering, or
>>>>even remove flickering if you flip the order of the inputs on the "divide".
>>>> Anyway, this may give you other ideas too.
>>>>
>>>>Regards,
>>>>James Rowell
>>>>
>>>>
>>>>
>>>>________________________________
>>>> From: Paul Schoen <dottore.pa...@gmail.com>
>>>>To: Nuke-users@support.thefoundry.co.uk
>>>>Sent: Saturday, May 12, 2012 5:26 AM
>>>>Subject: [Nuke-users] Analyze Brightness in a Region of Pixels to drive
>>>>Grade Node
>>>>
>>>>
>>>>Hello,
>>>>
>>>>this is my first post to the mailing list, so I hopefully get everything
>>>>right in explaining my particular problem:
>>>>
>>>>I have a composite of a Background in which feet are moving over a
>>>>pavement. As they move they make shadows on the pavement. The foreground is
>>>>moving spider that was filmed on the same pavement later on. Now I want the
>>>>brightness of my foreground to change exactly like the shadows of the
>>>>moving feet change the brightness of the pavement in the background.
>>>>
>>>>Long time ago, there was a node in Shake called AnalysePixel or something
>>>>like that which could read out a certain area of pixel over the whole
>>>>length of a shot. With this data one could drive the ColorCorrect-node to
>>>>automatically change the the brightness or any other value. I used it once
>>>>to match a non-flickering shot to a flickering one (NOT FLICKER REMOVAL!!!).
>>>>
>>>>I found nothing similar in Nuke except the Spotmeter-function in the
>>>>Viewer. But I found no hint to read its values and use it in an expression.
>>>>I need something to constantly analyze the brightness over a given range of
>>>>frames in a certain region of pixels and to drive a Grade or
>>>>ColorCorrect-Node with this values via an expression.
>>>>
>>>>Does anyone have any hints on this? I'm using Nuke 6.2v1.
>>>>
>>>>For convenience I uploaded the comp layout:
>>>>http://dl.dropbox.com/u/1891745/dpadb_022_lay_v01.mov
>>>>
>>>>Thanks,
>>>>
>>>>Paul Schoen, Vienna
>>>>
>>>>_______________________________________________
>>>>Nuke-users mailing list
>>>>Nuke-users@support.thefoundry.co.uk, http://forums.thefoundry.co.uk/
>>>>http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
>>>>
>>>>
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>>>
>>
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>>
>
>
>
>
--
>__________________________________________________
>Fredrik Pihl - visual effects supervisor - digital compositor
>UNITED IMAGE CREATORS AB
>rönnvägen 11, se-14144 huddinge, sweden
>+46-708-559 559
>
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>
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