
DIY True 4K Projector - humbfool2
https://youtu.be/YfvTjQ9MCwY
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huhtenberg
Since the right people might be reading through the comments here -

I've been looking at making a hi-res _ceiling_ projector for a living space.
Perhaps not one, but a set of several projectors with an overlap, but the key
point is that they need to be placed in a way so not to interfere with the
normal flow of life. Nor to be easily shadowed by people walking around, etc.
This (likely) mandates placing them around the room perimeter, possibly on the
walls at some height. This in turn means that they will be projecting at an
angle.

Do I understand correctly that it's not possible in principle to achieve
proper focus on the target surface when projecting at an angle like this? That
is if I am to project, say, a star field then it's not be possible to have
stars close to the projector and far from it to be both in focus at the same
time?

~~~
Someone
In principle, it is possible. A tilt-shift camera can bring any plane in
focus, so running it in reverse will project the image sharply on your
ceiling.

See
[https://en.wikipedia.org/wiki/Tilt–shift_photography](https://en.wikipedia.org/wiki/Tilt–shift_photography)
for cameras. [https://www.projectorcentral.com/Understanding-Lens-
Offset-a...](https://www.projectorcentral.com/Understanding-Lens-Offset-and-
Lens-Shift.htm) learnt me that you can buy projectors that use this method. I
suspect that back-projecting televisions ([https://en.wikipedia.org/wiki/Rear-
projection_television](https://en.wikipedia.org/wiki/Rear-
projection_television)) often use it, too.

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huhtenberg
Thanks, these are good leads.

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QuotedForTruth
My older Epson 8350 projector has a feature they call "Lens shift." When
setting it up you make sure that it is perpendicular to the screen surface.
Then it has two mechanical adjustments to vertically and horizontally shift
the image. Page 25 of this user manual shows that it can shift the image
vertically up to one image height up or down. And horizontally up to one half
image width either way. It makes setup a lot more flexible. I'm not sure how
common the feature is though on newer more available projectors.

[https://files.support.epson.com/pdf/plhc87u/plhc87uug.pdf](https://files.support.epson.com/pdf/plhc87u/plhc87uug.pdf)

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cmurphycode
This is so awesome! Back in 2008 I built a projector from an old unsued laptop
and a high powered metal halide overhead projector that I bought off ebay for
50 bucks. It was surprisingly good looking; I was very happy for the total
investment. It was unwieldy and pretty power hungry, but none of that really
mattered living in my college dorm at the time.

When the laptop screen eventually gave up (I think just the connector) I never
ended up rebuilding it. Nowadays you can get a really awesome looking
projector setup for so little, it's not really worth trying the same approach.

But from what I skimmed through, this is a build of way higher complexity,
cost, and quality. I'm looking forward to watching this video tonight.

~~~
Slartie
In 2006 or so I did the same, building a projector out of a laptop LCD
(without the laptop, just a plain LCD module and a controller), some lenses, a
fresnel lens (cut in half, one part before and one after the LCD) and a 400
watts mercury vapor lamp usually intended to be used to light up factory
halls. I constructed a housing for it from wood, a cooling system using lots
of PC fans to vent that 400 watts of heat, and even a microcontroller-based
control system for the entire thing, with a small LCD display, which managed
stuff like tracking bulb used time, monitoring internal temperature via a temp
sensor IC and letting the cooling system run for some time after turning off
the lamp to get the heat out.

That thing was heavy and loud as hell, and it wasn't very bright considering
it used 400 watts of light power, but it was about half the price of an
equivalent projector back then, which effectively allowed my poor student self
back then to enter the home cinema scene, which I couldn't have afforded
otherwise.

There even was an entire little scene back then of DIY projector enthusiasts
(at least in Germany) with bulletin boards and even some niche online shops
specialized in selling suitable lenses and LCDs and matching controller
boards. It was great fun and a great learning experience, especially since you
could get help from like-minded people and ideas from other people's projector
projects.

A few years later it all quickly went down the drain when the first Full-HD
projectors with acceptable quality dropped into price ranges that were
affordable for the general public. It simply wasn't possible to compete with
that anymore, neither in terms of quality nor in terms of price. I myself
replaced my hunk of a self-made projector after about 4 years of use or so,
with one of these entry-level full HD home cinema projectors (which I'm even
still using today, so that was a really good investment in my book). But that
self-made device was worth every cent and every hour of work, and I still have
fond memories of building it and tweaking it for maximum quality and then
watching movies with it, all the while thinking "man, I built that thing
basically from scratch".

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bserge
DIY Perks is a fantastic channel. So much good stuff, so little time to try
everything :D

~~~
ccurrens
I agree! I particularly liked the one using a two-way plastic mirror and
webcam, so that you can maintain eye contact when you're video calling
someone. Similar principal to a teleprompter.

[https://www.youtube.com/watch?v=2AecAXinars](https://www.youtube.com/watch?v=2AecAXinars)

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aidenn0
When you buy an expensive projector you are paying almost entirely for
brightness, so this result isn't too surprising.

~~~
radley
And HDMI 2.x, HDMI 2.x, power levels, & color settings.

Still, it looks like a fun project. I ended up watching the entire video.

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fenwick67
The super low-cost version of this is a magnifying glass and a shoebox - it
works surprisingly well if you're only throwing a few feet in a dark room.

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superasn
I never even knew Sony had released a 4k phone. What a clever way to kill two
birds with one stone: Get an android system with a 4k screen but for 1/5th the
price.

This guy is a true hacker.

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pengaru
A bit disingenuous for the presenter to completely ignore the obvious
vignetting of his dim projected image, the results seemed pretty mediocre from
where I'm sitting.

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ktm5j
I built a similar LCD projector when I was in high school! Same basic
principal as is used here, shine light through a bare LCD panel (mine was from
a broken laptop), add some fresnel lenses and a focusing lens and throw it all
in a box.

Pretty cool, but just buy a damn projector. Do not approach this as something
practical that's going to be useful, because it's not. It's huge, probably
loud, you'll get dust and stuff stuck in all sorts of places messing with the
image and it lacks advanced focusing like keystone transform
[https://en.wikipedia.org/wiki/Keystone_effect](https://en.wikipedia.org/wiki/Keystone_effect)

~~~
soylentcola
Yeah, we did something similar in our apartment in the early 2000's. It was
one of those old overhead projector/fresnel lens/repurposed monitor LCD panel
deals that were all over the internet at the time.

It was a cool project and when it was just me and a friend sharing an
apartment, we didn't care that it was janky (especially since any large format
screen was way too expensive for us at the time). But now you can get better
performance from a cheapo projector and for a bit more, you can even find
decent short-throw models these days.

My current project (that is collecting dust) is a big dual-lamp auditorium
sized Epson that I snagged when it was getting tossed out at work. Sadly,
while it was working when I picked it up, somewhere along the way from the
office and through a couple of moves the auto-iris got stuck/damaged.

It's the most frustrating thing because the projector works fine but when it
powers on, there's an error message stating that the auto iris has an error
and it won't let you proceed. I don't even care about the auto iris and while
I've dismantled it quite a bit and blown out/lubed everything I could find, I
still get the error. Apparently they all had this problem but it's way out of
warranty and I don't see much point in paying to have a free projector
repaired.

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lmilcin
This is marvelous.

Now imagine, with no right to repair, manufacturers locking all components
making these things impossible.

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mleonhard
He mentions that adding a reflector to the LED will reflect too much heat onto
the LCD. Could this be solved with a pane of glass between the LED and the LCD
to absorb the IR light?

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netsharc
The audio seems to be a let down though: plug something into the
(disassembled) phone's audio jack.

I wonder if phones can deal with USB audio cards (that have surround options),
or if there are any Bluetooth audio solutions that offer surround sound.

Or I guess you can replace the phone with a PC/laptop, and have the display
connected to an LVDS driver..

~~~
foobazzy
Wait. It's a phone. That means, it does have bluetooth. Or you can buy one of
those dongles that are basically like a wireless aux cable (I forget the
technical term for it)

Edit: Something of this sort: [https://crossbeats.com/collections/all-
products/products/con...](https://crossbeats.com/collections/all-
products/products/connect) (No affiliation to the company or the product)

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chooseaname
Interesting. I’ve been thinking of trying to find a decent projector that
operates off 12V for hurricane season. Something cheap because we’d not use it
too often. DIY might be an option. I don’t have access to any way to make the
metal panels like this one has though.

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ghostbrainalpha
Does hurricane season mean your family is camping out in the basement?

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chooseaname
Florida doesn’t do basements.

