Digital Picture to Analog Darkroom print

IMG_7283

regard_nocturneSince 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.

 

Recent developments 

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.

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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

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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.

IMG_7293b

 

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.

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cal2

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) :

bbb_anim

bbb-splash

 

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).

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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 :

IMG_7288

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 😉

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15 thoughts on “Digital Picture to Analog Darkroom print

  1. Pingback: Making paper darkroom prints from digital pictures #Photography « Adafruit Industries – Makers, hackers, artists, designers and engineers!

  2. Muphins

    Hi, I find the work you have done to be truly amazing ! All the calibration process is well described and the final result is really nice. It was a pleasant read.
    Oh, and I love the last picture !
    Good day!

    Reply
  3. Jochen

    Hi!

    Thanks For posting this. It’s great to find somebody that is doing this. There is very little experience yet discussed in the internet. I’ve done similar things with my iPhone 11 Pro and a 6 x 9 enlarger. The results are very good, and I don’t have the problems as you describe them. I get very smooth greys. I have done several A4 size prints and they render very smooth and nice. Cannot be distinguished from professional print. I tested enlargements up to 30×40 and resolution is still good! What is not optimal Is the control of contrast. The images have a very nice black and a very contrasty, but trying to reduce contrast and make the picture softer, has been very difficult. With the iPhone I can change the temperature of the display through night mode, this gives me colder and warmer white, which has a little effect, but not comparable to the control of a regular black and white in larger ahead. In my last experiments were using it for the filters, but still the pictures render more contrasty than I wish. I am not sure if this has to do with physics and the way how LEDs emit light, but I am at a loss at the moment how I can improve control. If you have experiences or an explanation for this and could give me a hint how to improve this, I would really appreciate it.

    Reply
    1. pierremuth Post author

      Hi Jochen,
      Thanks for your comment and your experience ! I’m happy as well to see someone else trying to find a solution to get proper b&w prints!
      In fact I think you are facing almost the same issue I had when I started, even if your phone screen contrast might be better than my LCD panel. At first I tried to use the grayscale of my display, and observe high contrast as well. So to compensate this, I changed the dynamic of the source image using the transfer curve. But doing so give banding as the screen grayscale resolution is 8bits, or 256 tones.
      As far as I understood, this is due to the response curve of the paper. The response of the paper to the light intensity is not linear and should be rather the same as the film negative. And of course your screen doesn’t have the same response curve regarding the requested grays.
      You probably know the “double exposure” method for black and white print from film, on multigrade paper. You expose half of the time with a high contrast filter, and the other half with a low contrast filter. This to have control of the dynamic range.
      It is a pending idea I have for my LCD as well, to expose several versions of grayscale image.
      Maybe you can “de-saturate” your contrast with double exposure as well. Expose a normal version of your picture for half of the time, then expose a very “de-contrasted” version for the other half. This might be enough to avoid to expose each gray values the right amount of time as I did.
      Hope that helps, and of course don’t hesitate if you have questions. I’m curious to see your setup and results, don’t hesitate to share a link here if you have things online.
      Have a nice day,
      Pierre

      Reply
  4. Pierre

    Hi!
    I came across this very good post while searching the web for ways to produce digital negatives. I’m indeed very keen to dive into “alternative printing processes” (cyanotype, carbon transfer, …) which are based on exposure under UV light, but, as someone commented elsewhere on your work, printing digital negatives kind of holds me back a little bit… Indeed as image processing workflow is mainly digital nowadays (often too when shooting film), it is appealing to keep its convenience (control/reproducibility) down to the very last step before the image takes physical shape. For that matter your work should be of great interest to people involved in alternative printing processes, as it illustrates that such processes are to most extent a special case of masked (stereo)lithography (MSLA) a rising technology in 3D printing. Though I don’t have any experience in darkroom printing, I feel that your approach delivers surprisingly well. Kudos and thank you for sharing it!
    If I may, I have a couple of questions:
    – When you compare your print with the professional one, you mention that you intentionally lowered contrast and sharpening, does that mean that you may have come closer to the professional print if you had wanted to?
    – The close-ups indeed show less contrast/dynamic range, details in your print, have you since then made further progress with the fine tuning of the calibration curve? May the thickness of the panel cause some kind of diffusion consequently softening the projected image? Would a “collimated” light source bring improvements?
    – Vertical lines artifact is something that could possibly turn photo enthusiasts away from this approach; I’m wondering what is causing that. According to you, is it hardware or software (graphic driver) related? I’ve quickly looked into feedback on MSLA 3D printers, which use similar LCD panels, but it is unclear if reported artifacts could echo what you are noticing. Would some kind of pixel-shift technique (shift LCD mask while adjusting it accordingly) be way to fix that?
    Thank you for your feedback
    Have a nice day

    Reply
    1. pierremuth Post author

      Thanks a lot for your comment! And your very interesting questions.
      – I think I can get close to the pro prints rendering, regarding contrast and accentuation. The company’s process somehow put the accentuation cursor a bit too far in my opinion. My version is without digital accentuation, thus the softness.
      – I cannot really measure the dynamic range, whereas for the contrast it was by choice during my digital treatment. However you’re right, the calibration curve still needs some adjustments, in particular for the bright grays. I suppose the light of the enlarger is enough directional, as the LCD pixels are visible on the paper. You’re probably right about the thickness, the dark pixels tend to spill like half a pixel in the surroundings, results of the absorbing part of the LCD is slightly too far from the paper. (first glass layer thickness)
      – The lines are, I think, purely hardware related. On the LCD, there are tiny gaps between pixel lines, with I presume an electric conductive track. I didn’t perform tests by using the 3 sub-pixels. These LCD panel are the same as color one but without the RGB filter. In my case I use B&W images, so all the 3 sub-pixel are on or off.
      Hope that helped, don’t hesitate !
      Have a nice day too,
      Pierre

      Reply
      1. Pierre

        Hi again,
        Thank you for your prompt feedback and your explanations!
        As much as I can see in the close-up as well as in the pattern test print, line artifacts don’t seem to be present in purest whites as well as in very deeper blacks, while it’s very “obvious” in “mid tones” where lines tend to have the same “thickness” as the pixels themselves. That puzzles me a little. I mean, does it fit to the assumption that lines relate to panel internal wiring? Shouldn’t deeper blacks exhibit white lines then? That’s why I was inclined to suspect something related to the way the graphic card handles the animation, refreshes pixels… But maybe the tonal differences I point above have to do with the spill effect induced by the refraction though the panel material (what is the thickness of the panel?)…
        Your remark on the 3 subpixels is interesting. Digging further, I’ve realized that there seems to be two kinds of monochrome LCD. Some are customized “color” LCD with 3 sub-pixels, others are claimed to exhibit no subpixel . Maybe the later behaves differently…
        Best

  5. Pingback: Night reading 4K monochrome LCD display | About using electronic stuff

    1. pierremuth Post author

      Yeah, I hope he is not too upset about this. I was listening to him while testing the screen. And when I wrote this post, I realized I only had this picture of the screen before I mounted it in the frame.
      Thanks for your nice words !

      Reply
      1. Abdula

        Good afternoon!
        Maybe you can tell me – how to run your program?
        I tried to run it in Windows 10 and nothing happened.
        I have the latest version of java installed.
        I also tried to run it via .bat file
        (start cmd /k java -cp C:\1\Calibrator.java) and it just pops up black for a second and then disappears.
        Unfortunately I am not really good at programming and I must be doing something wrong.
        I would be sincerely grateful to you if you could help me.
        By the way, on my screen with about the same density (I have 270ppi) I was able to completely remove the pixel raster when transferred to photographic paper with minimal loss of detail.
        I applied a filter in front of the screen (matte film from a perforated pocket, tread sheet) – the image lost a little detail, but when magnified through a magnifier no pixels are visible, the texture of the matte film became visible – it is quite shallow, chaotic and much more pleasing to the eye.

      2. pierremuth Post author

        Hello !
        Thanks a lot for the filter idea ! It is very clever and can be adjusted with different grain density !
        To launch the program, I’ve updated the Git repo with a complied Jar file -> https://github.com/pierre-muth/Digital-Picture-to-Analog-Darkroom-print/tree/master/DigitalToAnalogPhotography/jar
        Could you try with > java -jar GrayScalePlayer.jar ?
        Then on the interface you’ll have a button to choose you image file, and then a start button to play the sequence. I still have to find a way to customize the curve gray vs time with the interface and not by modifying the program.
        Hope that helps

  6. Abdula

    Thank you, it all worked!

    Yes, the ability to adjust the gray level curve would be a very useful addition.

    Please tell me, is there any way to save the final result to a file (something like .gif)?
    I can do something radical and record in video format via screen capture, but what good would that do? That’s probably not the right way.

    Reply
  7. pierremuth Post author

    Hi ! I’m pleased that works on your side as well!
    A video capture should work I suppose, with a very low compression ratio, or lossless format to avoid artifacts.
    It is technically possible to generate a Gif file, as far as I remember, each frame can have a different timing. I will try to find some time to search on that.

    Reply

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