Cherry Kino

Cherry Kino

Monday, 4 April 2011

DIY Colour Separation in Film





Above: 3part Harmony: Composition in RGB #1, by Amanda D. Christie

This is an email sent by the ace filmmaker Amanda Dawn Christie, to the Frameworks list, about how to do colour separation the simple way (she has done it many ways, including a very labour intensive way, like in the image above). It's always brill to find out about good and fairly simple DIY techniques! Her films are great, and distributed by Light Cone and CFMDC.


Ah yes... doing it all in camera from the get go and the filters...

It can be quite simple really.
You can see some other examples (more fluid and less precise) of
colour separation in the opening sequence of my film "Fallen
Flags" (the first minute is black, but after that, the roof of a
train is colour separated from a single piece of colour source film.
You can also see an example of colour separation from a single piece
of black and white in my film "Knowledge of Good and Evil" (the scene
where I am swimming toward the camera under water and the colours
trail from my hands and arms)



Above: Fallen Flags, by Amanda D. Christie

I'll try to quickly describe a bit more clearly about additive and
subtractive primaries and how the filters work.

LIGHT AND COLOUR:
all light (even seemingly white or colourless light) is made up of
various colours.

ADDITIVE PRIMARIES: Red, Green, and Blue (RGB)
Red + Green + Blue = White LIght

SUBTRACTIVE PRIMARIES: Cyan, Magenta, Yellow (CMY)
White - Red = Cyan
White - Green = Magenta
White - Blue = Yellow

(and it gets more complicated from there and there are some lovely
diagrams and colour wheels showing how you can add and subtract them
from each other... but those are the basics... think additive, because
RGB added together = white... and the subtractive ones are what you
get when you subtract either RG or B from white.

WAVELENGTHS AND FILTERS
Light is made up of various wavelengths. Each different wavelength is
a different colour.
If you want to use true RGB filters to do colour separation, you want
to choose 3 filters, that will INCLUDE all of the wavelengths but that
will not have too too much overlap with each other... you want them to
be discrete... the tricky part comes in the borders between the
colours... you either wind up with a gap or with overlap.

MAKING THE RECORD (WAS REFERRED TO A MATRIX IN THE DYE TRANSFER ERA OF
TECHNICOLOUR)
if you film onto black and white film, with no filter... you have a BW
record of the light... that photographic image is a record of all of
the wavelengths (depending on which wavenlengths the emulsion was
sensitive to, of course... but that's another topic all together... so
let's assume we have an emulsion that is equally sensitive to all
wavelengths.. ha!)

to see this illustrated clearly, imagine a woman's face with pale
skin, freckles, green eyes, and bright red lips.
now, if you take a photo on black and white film with a red filter on
the lens, her freckles and lips will be very pale... it will be a
black and white image but her skin tone and lips will be quite pale,
and her eyes will be almost black... if you do this with a green
filter, then the freckles and the lips will pop like crazy and you
will see lots of texture on her face, but her eyes will be very pale.
you can try this out really easily in photoshop if you take a colour
image, and then go into your channels panel, and just look at the red,
green, or blue channel alone... you will see a black and white
image... but each of the three black and white images will be very
different. each black and white image is a record of something
totally different... one is just the red light, one is just the green
light, and one is just the blue light.



Above: Colour Separation, by Chris Welsby

okay... so colour theory aside... here's some practical easy stuff you
can do.

DOING IT IN CAMERA (NO OPTICAL PRINTER NECESSARY)
load your camera with colour film.
slap on a red filter
film
rewind the camera
slap on a green filter
film
rewind the camera
slap on a blue filter
film.
process it
ta-da!

DOING IT IN THE OPTICAL PRINTER FROM COLOUR SOURCE FOOTAGE
same as above

DOING IT IN THE OPTICAL PRINTER FROM BW SOURCE FOOTAGE
you can take a single piece of BW source footage and print 3 times
onto colour film, through RGB filters, and if you throw each layer out
of sync by just a few frames in each pass, you get a black and white
image with gentle trails of RGB and CMY at the edges where there is
movement.

phew... again... lots of info.
it's hard to describe this stuff without visuals.

hope that was somewhat clear and useful.

amanda

THANKS AMANDA! xx




Above: 3part Harmony: Composition in RGB #1, by Amanda D. Christie

x Martha

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