
Antique 4x5 camera creates 20 micron photolithography masks [video] - EvanAnderson
https://www.youtube.com/watch?v=YAPt_DcWAvw
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canada_dry
Ben Krasnow (a Googler by day) has one of the most incredibly interesting
channels on youtube - and accompanying blog [1].

The effortless way he is able to describe complex processes and techniques
used in his experiments borders on being _Feynman like_.

[1] [https://benkrasnow.blogspot.com/](https://benkrasnow.blogspot.com/)

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ddingus
I agree. He's a treasure, and I've learned so much. And learned it fairly
easily.

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bkraz
Hi. I'm the creator of this video. Let me know if you have any questions.

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bane
Awesome video and process, we've been talking about this at work since it
showed up here and have a few questions if you don't mind:

How far do you think you'd be from making a simple 8-bit CPU like a 6502?

Have you thought about illuminating the initial film exposure as well as the
substrate exposure (on the slide glass) using monochromatic light sources like
a mercury UV lamp?

Instead of a vacuum pump to flatten the film during exposure, how about
electrostatic charges?

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bkraz
Thanks! I'm very far from making a CPU. Check out Sam Zeloof's work to see
some of the other parts of home IC fabrication. Creating the mask is just one
part of the process, and dialing in diffusion, oxide growth, metal deposition
would take a lot of additional effort.

Yes. My original attempt (years ago) was to use a standard photographic
enlarger: replace the lens with quartz, place the paper or plastic master
design on a UV light source on the table, then place the microscope slide with
photoresist in the enlarger where the film would normally go. One problem is
the lens is not setup to cover a whole microscope slide. Another problem is
not enough UV light getting through the whole optical system -- exposure would
have been hours if it worked at all.

Haven't tried electrostatic. Considered low-tack adhesive (3M post-it).

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madaxe_again
I used to travel with a crown graphic - pretty much the same camera as in the
video, shooting colour positive. You can do some great stuff with them, and
tilt-shift is trivial, if that’s your thing. Quality on slow film is just
crazy - I’ve a shot of an ex, she’s half-frame, and you can see the second
hand on her watch - you can get very fine focus with a loupe, and having a
Polaroid back to do some instant tests was a godsend - but you can’t get the
film for it any more.

I have no idea where he’s finding film so cheap - I stopped when it was
costing me £5 per exposure.

It also folded up into a very neat little box, which is irresistible to
children - sadly one was handed it by a friend, who promptly destroyed it.

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Palomides
I literally just bought a box of the film he's using here, it's a high
contrast red-insensitive film, $15 for 50 sheets,
[https://www.freestylephoto.biz/531345-Arista-Ortho-Litho-
Fil...](https://www.freestylephoto.biz/531345-Arista-Ortho-Litho-
Film-3.0-3.9x4.9-50-Sheets-For-4x5-Film-Holders)

developing it for normal contrast images is more difficult but not impossible

~~~
staticautomatic
I've shot a ton of Kodak Ortho film in 4x5 at EI 3, 6, and 12. It's actually
super easy to develop. I recommend stand development in 1:100 HC-110 with
occasional agitation. The developer basically exhausts after 10 or 12 minutes
depending on the temperature, which happens to be pretty much exactly the
right development time, so it's pretty much impossible to over-develop.

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bane
One of my coworkers did his dissertation on photolithography, I grew up in a
family printing shop and we followed a remarkably similar process to generate
the metal offset plates that were used in the presses. It turns out that the
processes are so similar that my colleague and I often frequently remark about
it during idle chit-chat.

There's pitifully few good explanation videos about the printing version of
this process, but here's a quick video (in Chinese, but if you watch the OP's
video this one should be easy to follow)
[https://www.youtube.com/watch?v=KENIyBWNhyk](https://www.youtube.com/watch?v=KENIyBWNhyk)

The process in the printing industry has gotten very refined as well: you can
go directly from a digital image file to a plate in one entirely automated
step:

[https://youtu.be/mA8Dnp0rp3Y](https://youtu.be/mA8Dnp0rp3Y)

[https://youtu.be/TeJ_STTfBsI](https://youtu.be/TeJ_STTfBsI)

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cculpepper
Ben's interview on The Amp Hour [0] is pretty great as well. Awesome person,
amazingly the same in person as in his video persona.

[0] [https://theamphour.com/480-an-interview-with-ben-
krasnow-8-y...](https://theamphour.com/480-an-interview-with-ben-
krasnow-8-years-on/)

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chongli
This is so cool! Questions for engineers:

How much work would it take to go from this process to producing a working
chip in his garage, like a 6502 or something? Would it be at all feasible? He
did point out a ton of defects in the final product, probably due to dust or
scratches in his equipment/materials. Would it be possible to clean this up
enough to get 1-2 usable chips from a single sheet of 4x5 film? Without
turning his garage into a clean room?

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Cerium
Here is a blog on home IC production: [http://sam.zeloof.xyz/first-
ic/](http://sam.zeloof.xyz/first-ic/)

Having done some work in a university lab, I have no desire to be involved in
silicon work in a home environment. It requires dangerous chemicals, and lots
of equipment and dedication.

A short list of what I remember: \- Spin coater \- Some solution of exposure
of masks \- Various chemical baths (HH, piranha, etc) in a dedicated area. \-
Inspection microscope \- Tube oven \- Vapor deposition \- A way to measure
film thickness

~~~
chongli
I wonder if at some point we'll develop new materials and techniques that make
it easier to do this, with safer chemicals and less equipment. It may seem
far-fetched but you never know. When I was a kid I would've thought it pretty
far-fetched that people could 3D print ventilator valves at home that are
actually saving lives during a pandemic.

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itgoon
Applied Science is one of my favorite YouTube channels.

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splintercell
Cringing it everytime he calls it an antique camera.

This is like a millennial talking about an antique technology called 'VHS'
tape.

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tasty_freeze
Go to craigslist (for a large city) or ebay and search "vintage computer".
Stuff produced in the 90s is considered vintage.

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foldr
Vintage != antique, and ginko is absolutely right. You can buy the exact same
kind of camera brand new today:

[https://peartreephoto.com/sinar-p3-view-
cameras/sinar-p3-df?...](https://peartreephoto.com/sinar-p3-view-
cameras/sinar-p3-df?gclid=EAIaIQobChMIrtS2k6rE6AIVCLTtCh0UbwYdEAAYASAAEgLWZ_D_BwE)

(Ignore all the marketing copy about digital. Anyone dropping this amount of
money on a monorail probably would be using it with a high-end digital back,
but that's not included in the price, and the camera above could perfectly
well be used with a film back too.)

