Re: DPX reader vs. Northlight scans with infra-red pass

On 26 Aug 2008, at 21:22, Bob Friesenhahn wrote:
> I know that the dust channel is definitely being used by some  
> software.  I saw an impressive demo of it's use several years ago.

Absolutely - the idea is that PFClean uses it to clean the plates  
then we get them as normal DPXs.  However sometimes this doesn't  
quite happen :)

> It is likely pretty easy to update GraphicsMagick so that it will  
> read this format.  It could ignore the extra channel, or it could  
> use the one bit depth plus the "NL CLEAN MATTE" description to  
> decide that it must be in the alternate format.  The main problem  
> comes when writing since then GM would need to know if it should  
> write this non-standard channel format and it needs to know that  
> the alpha channel is 1 bit.

What would work well for me personally would be an option to write  
the alpha using this format.  I can imagine sometimes wanting to copy  
the alpha information from a scanned sequence into a rendered  
sequence, for which that'd be handy.  For reading, I don't see any  
advantage to keeping it as 1bit if that creates problems transporting  
it to other file formats - for example if converting a sequence to  
TIFFs it seems reasonable for the alpha to be bumped up to 16bits to  
match the colour channels.

One thing I'm thinking of is to use gm to change metadata in  
sequences - at the minute I can't seem to get this to work, using "gm  
mogrify -define dpx:mp.frame.rate=25 0899992.dpx" for example.   
Happily I can use "gm identify -format '%[dpx:*]' 0899992.dpx" to  
quickly get the metadata - very pleased to see that it does this  
without reading the image, unlike Shake which I was previously using  
to extract the information.  An order of magnitude faster!

Again thanks for all your hard work,

-- 
Lewis Saunders
Compositor
Molinare, London


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