[Tig] scanning from Swinson

Rob Lingelbach rob
Sun Feb 13 19:35:29 GMT 2005


{editor's note: this will go into a new section of tech articles with
the jpg in a few moments... watch for it}

A few people have asked me about the colormetrics of scanning.
As Kevin Wheatley  from Cinesite UK  pointed out there is always more 
to life than one expects !
Keith made reference to SMPTE RP 180 which defines the taking
characteristics for film scanners.
Whether they are adhered to or not is another matter.

However I took the SMPTE figures into MS excel and plotted them. I then
overlaid them onto a typical Kodak neg stock 5277. 
I only used the old Vision 5277 curves because  Kodak's leaflet shows 
them more clearly than the Vision 2 leaflets

The results may be of interest.

Rob, Can you place a pointer to the location of the graphical image?

They clearly show how the SMPTE response includes the scan detectors 
being effected by color dyes other than the dye layer of interest, in the 
same way that print stock would "see" the negative.

Scanner heads can siumulate this in one of two ways.
By matching the RP 180, this has the advantage of gathering most light,
area under the curve = volume of photons.  
Or Have narrow band sensors and then electronically  simulate the "bleed" 
of unwanted dye layers into the channels by matrix/masking.

There are other other devils in the detail, but I guess if they were 
all revealed, everyone would be building scanners!!!!    

It would be interesting to hear from the Viper and other Electronic
aqcuistioners out there whether these cameras  follow these "filmic"
characteristics.  I have long believed that the native Viper 
"greenish" cast is due to this attempt to match negative film dyes. Is it?   

Time to descend into the bunker and avoid the flak


Peter Swinson

-- 
Rob Lingelbach   
http://www.colorist.org





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