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'Multiply' Composite Mode makes box around image. How to fix?

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Glenn Camhi
'Multiply' Composite Mode makes box around image. How to fix?
on Jul 27, 2011 at 1:18:00 am

(Oops, edited to correct the composite mode I'm using)

This seems to be a bug, though I may be missing something obvious here. I've laid an image that's dark with a white background on a track. I'm using the "Multiply" Composite Mode to make the white area transparent, so only the dark shape is visible on the track below.

However, this Composite Mode strangely turns the borders of the image file dark, so I've got a thin black box around the image which looks bad (and makes no sense). Why is this happening, and how can I eliminate it?

The original image has no actual border, I've verified it's pure white pixels all the way to the edges. I tried making a four-point matte to mask off the edges, but the matte lines simply produce new dark borders. The image is much smaller than the frame, so I can't hide the edges off frame.

Thanks for any help!


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adam taylor
Re: 'Multiply' Composite Mode makes box around image. How to fix?
on Jul 27, 2011 at 7:40:48 am

try using the "crop" settings in the motion tab, to trim away the edges that are giving you problems.

Adam Taylor
Video Editor/Audio Mixer/ Compositor/Motion GFX/Barista
Character Options Ltd
Oldham, UK

http://www.sculptedbliss.co.uk
My YouTube Animations Page


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Glenn Camhi
Re: 'Multiply' Composite Mode makes box around image. How to fix?
on Jul 27, 2011 at 8:02:28 am

Thank you very much, Adam. That did it.


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Rafael Amador
Re: 'Multiply' Composite Mode makes box around image. How to fix?
on Jul 27, 2011 at 6:05:05 pm

[Glenn Camhi] "gh I may be missing something obvious here. I've laid an image that's dark with a white background on a track. I'm using the "Multiply" Composite Mode to make the white area transparent, so only the dark shape is visible on the track below.

However, this Composite Mode strangely turns the borders of the image file dark, so I've got a thin black box around the image which looks bad (and makes no sense). Why is this happening, and how can I eliminate it?"

That happens because the Multiply mode doesn't works like you think.
Your method will works only when the picture you overlay is B&W (Gray scale): Only Luma.
Will works as a Luma matte.: Full transparency on the white and no transparency on the Blacks.

A "dark" picture doesn't works because there is Chroma, and the chroma will be be multiplied too.
Edged wont be clean.
rafael

http://www.nagavideo.com


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Glenn Camhi
Re: 'Multiply' Composite Mode makes box around image. How to fix?
on Jul 27, 2011 at 6:24:56 pm

[Rafael Amador] "That happens because the Multiply mode doesn't works like you think.
Your method will works only when the picture you overlay is B&W (Gray scale): Only Luma."


I am working with a grayscale image. Sorry, I didn't mean "dark" to imply color... I didn't think to specify since I assumed B&W was a given. I've long worked with Multiply (and other blending modes) in PS, not as much in FCP.


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Rafael Amador
Re: 'Multiply' Composite Mode makes box around image. How to fix?
on Jul 27, 2011 at 9:24:33 pm

Hi Glenn,
Your issue may be related with the codecs you are using.
I don't know which is your footage and sequence setting, but try changing the sequence codec to Prores, and set "Render in High Precision". This should help with graphics.
rafael

http://www.nagavideo.com


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Glenn Camhi
Re: 'Multiply' Composite Mode makes box around image. How to fix?
on Jul 27, 2011 at 11:51:46 pm

Thanks very much, Rafael. Codec is ProRes 422 (HQ), and "Render 10-Bit material in high-precision YUV" is set. I can try "Render all YUV material in high-precision YUV," but since the crop did the trick for now, I'll experiment later and report back. I appreciate the help.


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