Projector Cyanotype and Chiba python digital negative.

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Today I looked into calibrating UV focus. Holy moly! Look at that! My focus was at zero in visible light but in UV it's shown at 16 or more in this chart.
The card was at 45 degrees, the distance to 16 mark from 0 is 76mm so it means that I have to focus my projector 54mm in front of the actual photo. And I just did my first image with these changes and boy! wow! its nice!

 

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But one thing I noted was that the focus 54mm away is around 10%. Every footnote i've read says that UV focuses 5 to 10% in front of visible light. Here for whatever reason, the UV light is focusing 10% behind visible. I guess I should not really expect a particular number or direction since lens makers can pretty much swing the focal plane any way they want. Any comment or opinion on this? The lens on this projector is weird. It has this sort of central pinch to it. Like the center part of the lens looks almost flat if not reversed inward. I thought it was maybe parabolic or hyperbolic or something. but if you look from the side you don't see the typical parabola shape, you see this center pinch. The same with the light's lens. I think they are playing some sort of focal plane correction from both sides of the optical chain.

 

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OK So last week I worked on the focus thing. Today I gave up on processing the images locally on the little thinkcentre computer. Instead I went back to Mr ChatGPT and I asked it to build me an HTML page and serve it locally using podman. The benefit of this is that you can have a big powerful computer do the image crunching and a tiny computer do the projecting. It can be the same computer it doesn't matter. To use it:

You will need Ubuntu or some other Linux. I don't do windows programs sorry for you if you must use windows:
first allow the network traffic :
sudo ufw allow 5000
Then
podman run -d -p 5000:5000 my-flask-app

it looks like this:

then just open an email file, hit process image. That will start the threshold as a series of images in a cache folder on the server. then when it is done, go hit start or stop. Oh and input your exposure time. Its really working finally!! like if you set it to 12minutes it will expose for 12 minutes!


One last bit. On Firefox (friends don't let friends use chrome anymore) go to : about:config and then search for "full-screen-api.ignore-widgets" double click her to set it to true. Now if you press F11, the top menus of your browser will disappear and you will have a single window with your image ready to go. Hit start then take the pointer and put it somewhere else so the menus autohide. Its working OK. It probably needs some TLC but I am not complaining.

my projector is 1080p, but you can change the native resolution in the python app called app.py:

 

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I'm following this recipe: https://lemmy.world/post/26591859 and I'm getting photographic level resolution on my cyanotypes. On textured paper its interesting because you can Illuminate it directly overhead and see the resolution you saw when it was wet, but as soon as the illumination comes from elsewhere it looks like a regular slightly blurry cyanotype. On glass and plastic as well as flat photo paper it keeps its full resolution. The formula comes from the latest experiments by Habib Saidane but are modified and a completely separate thing. The tissue poured with the sensitizer doesn't actually dissolve away when developed in water. the image is embedded inside of it. The formula seems to clear to paper-white unless you use some sort of staining liquid.