The aim of this project was to display a colour image on a black and white monitor, by overlaying an acetate bayer filter (inkjet printed) over the monitor and mosaicing a colour image.
I obtained an Eizo B&W monitor from ebay, which I was intending for use viewing B&W photos and was curious if I could replicate an effect similar to Autochrome Lumière ( see wikipedia ) where they overlay colour filters over a B&W photographic plate, using starch grains, which creates a colour image.
The following image shows a 500x microscope image of the pixels that make up the B&W LCD display, taken using a cheap USB microscope. It looks to me as if each pixel, is represented by 4 sub-pixel elements, please correct me if this appears not be the case. (Edit: It seems a pixel is 3 groups of ‘<‘ shapes, see below for more information)
A pdf was created of the bayer pattern, with the dimensions 433.1mm x 324.8mm. The monitor has a resolution of 2048×1536 and I assumed the pixels had the same width as height.
You can see an example of the pdf I created below, where for example a blue element, should be represented by 2×2 pixels from the B&W monitor.
I created 3 pdfs:
- bayer_1.pdf – each element, is represented by 1 pixel from the display
- bayer_2.pdf – each element, is represented by 2×2 pixels from the display (this is the acetate used in the video)
- bayer_4.pdf – each element is represented by 4×4 pixels from the display
The following image shows the printed acetate with the bayer pattern:
The following, is a B&W image with mosaicing applied from the colour image:
How it works
The monitor I am using seems to generally be used portrait, to make it landscape on linux:
xrandr --output HDMI1 --rotate left
Image of effect
As you can see the effect of my attempt is quite slight, but you can see in the centre the different colours of the balloons.
Video of effect using inkjet printed acetate
The effect is also demonstrated in the following video, with the following parameters:
mpv out.mkv --fullscreen --loop --brightness=10 --contrast=20
Microscope images of the bayer filter (2×2 scaling)
2×2 bayer filter, I tried to design it so that for example the ‘red’ square covers 2×2 pixels on the monitor
As suggested by Olivier, I’ve just created 2 chess board images. Olivier was correct that a single pixel consists of 3 sub-pixels 🙂
1×1 (the white patch is 1 pixel), monitor in landscape, image in correct orientation from microscope (left, towards left monitor, top, towards top of monitor)
I made use of a 2×2 chess pattern and a 1mm microscope micrometer with 100 divisions. By my initial calculations I anticipated around 0.42mm x 0.42mm for the size of each black/white block, which seems to roughly tally with the measurements below.
It was hard to get both the pixels and rule in focus at the same time, I used the micrometer slide upside down also, so the print was closer to the pixels, as the microscope has a very shallow focal plane.
Using the micrometer in a vertical orientation, to measure the size of the ‘chess’ squares.
I found it was better to use the microscope micrometer as calibration for the microscope, rather than a ruler. I took a photo of the micrometer at 500x magnification. I made a simple script that determines the positions of the lines and measures the total length of the micrometer at 1mm. This told me 1241.5 pixels equates to 1mm.
Using the values from my initial calculations combining the width of the panel and the number of pixels which means 0.21mm x 0.21mm for each pixel.
I used the value from the micrometer of 1241.5 pixels for 1mm and did:
0.21147460937*1241.5 = 262.5
= 263 pixels for a pixel width/height and drew lines every 263 pixels, for the centre of the image
Which seems to indicate a value of 0.21mm x 0.21mm seems sensible.
I wonder if by measuring the exact pixel width/height under a microscope, if the effect could possibly be improved somewhat, as that information could be used when creating the acetate filter.
- I have tried this now and think the values I’ve chosen seem sensible
Alignment is also a key issue, I need to think of ways to improve that, possibly using a microscope while aligning the acetate.
The following image shows the inkjet acetate, I’m wondering if using a photographic developing process (such as duraclear) instead may give better results.
- See the video at the bottom of the page for improved results using duraclear
I’d be interested in other improvements I could make too!
New improved attempt using duraclear
The following video depicts a new attempt using a photographically developed film known as duraclear:
The sourcecode to generate the PDFs for the acetate and the mosaiced images and videos is at: