Since 2008, I am using almost exclusively a digital camera. But I am always missing the black and white darkroom prints.
From time to time, I order paper prints of my pictures using online services. They are very good now, especially for color prints. However, and
probably due to my picky nature, I’m not impressed by the prints in black and white. Each time I put side to side a professional print with an old print I did in the dark room, I see a difference in tone. Perhaps it is because of the use of color paper event for black and white prints.
But I’m using my film camera very rarely now, almost all my pictures from the last decade are digital. I know it can sounds heretic for true black and white film lovers, but I always had this in mind – how could we transfert a digital image onto a true analog sensitive black and white paper.
Some resin 3D printers uses a monochrome LCD screen. Monochrome because the UV light is not absorbed by the color filter of the usual color LCD. As there is now a small market for these kind of displays, we can now find rather large panels with high resolution.
This is a 13″ LCD, monochrome, and 4K resolution. It means 3840 x 2160 pixels – more than 8 Megapixels – and a density of 330 pixel/inch (1 pixel is 76 micron). There is no back-light, and it connects easily to a computer HDMI port through an adaptation board. I bought it from Duobond Displays Shenzhen here.
Usually 300 dpi (dot per inch) is used for prints. It could be more dense of course, but it is what I observe on the photographic prints I get from professionals. (See later for close up pictures).
Make a protective frame
The LCD panel is fragile, better to make a frame to handle it safely.
Put back the the darkroom in place
I removed the dust from the projector, get the 3 chemicals and black and white paper. I spent a bit of time to make the cave lightproof, but after all it is not very complicated.
After the first test, I was happy to see that the LCD is perfectly able to block the light with black pixels and let enough light to pass through with white pixels. Making on the paper respectively white and black pixels.
The LCD is put in contact with the paper, the same way we make contact sheets with films. On the images above are the setup with the projector and the LCD panel, a test mosaic, and the result on the paper. The scale on the left is millimeters.
Find a transfer function
I tried first to tune the LCD panel grayscale using, among others, the gamma value of the picture. Actually the paper and the film have the same light sensibility, only the film has a negative image. And this is not linear compare to my digital LCD panel.
In order to get a reasonably good gray gradient, I had to change too much the picture values. So much that I get artifacts on the paper, the result of a loss in the tones resolution. Even with the source raw 14bits image, I got banding (aliasing) between light gray values. Because the screen itself has a tone resolution of 8 bits: 256 different shades of gray.
Using time to generate grays
As a friend advised me, the solution is to use the exposure time to generate smooth gray values: like resin 3D printers do with each layers, here exposing an area longer will give darker tones.
I made a small program to expose square tiles of the paper with different times. The idea is to get a calibration curve.
After several attempts I got a curve: time in function of darkness.
It appears that another phenomenon should be taken in account: the paper takes 1 or 2 seconds to react. Then it is very sensible for the first 15 seconds, then it gradually looses reactivity, so it takes longer to have a slightly darker black.
The next step is to make a program that translate the tone value into time, and generate the animation. See below the famous Big Buck Bunny as an example (the time between each values is constant on the GIF, but not when generated with the program) :
Comparisons and outlook
It is indeed quite hard to show with pictures the different feelings of prints. Below, on the left is a professional print with their tunings and on the right is the black and white Ilford paper with my own settings (less contrast and less digital sharpening).
There is still room for improvements, especially on the light tones, but I prefer the true blacks of the b&w paper. It is difficult to see, and I’m very picky, but the professional print is a bit greenish. On the other hand, the black and white paper is by definition unable to produce colors.
To come back on the resolution, here is some close up of these prints :
Pixels are visible on both prints and are about the same size. However, the LCD leaves tiny vertical lignes.
I let you make your own conclusions. But I can give you my feelings. I think it is a good solution to get digital pictures printed on a true black and white paper. It will not be better than a print from a film or high quality prints from a professional. However it gives good result in roughly 6 min. One minute for exposure, 2 minutes revelation bath, 1 minute stop bath, and 2 for the fixing bath. Rinse with water, et voilà 😉