[HN Gopher] DIY "infinity contrast" TV - with 100% recycled part...
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DIY "infinity contrast" TV - with 100% recycled parts [video]
Author : HelloUsername
Score : 101 points
Date : 2025-03-04 14:55 UTC (8 hours ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| gibibit wrote:
| A bit clickbait calling it "infinity contrast" even if it's
| higher contrast than an LCD, is it still a finite contrast.
| Probably not higher contrast than modern OLED TVs, but a clever
| hack with stuff at hand. Just not up to the hype of infinite.
| nickthegreek wrote:
| Not sure I would call that clickbait when the Creator put that
| phrase in quotes in the original video title.
| smusamashah wrote:
| FIY, current substitute title (using DeArrow chrome
| extension) is "DIY Rear-Projection TV - Recycling Broken TV
| And A Projector"
| Kirby64 wrote:
| The author is using a DLP projector to backlight the LCD. When
| the projector is displaying black it effectively is infinite
| contrast. The light is reflected away and never reaches the LCD
| to backlight it.
| smusamashah wrote:
| Black color coming from projector isn't full black either
| https://www.projectorreviews.com/articles-
| guides/projector-b...
| gibibit wrote:
| Good point, I hadn't even thought of this.
| mbreese wrote:
| True, but for this purpose, it's "blacker" than a typical
| LED backlit TV. For a Youtube / DIY project ... I think the
| description is fine.
| wdfx wrote:
| He also did not do (or at least did not mention) anything
| about the reflected/diffused and ambient light behind and
| around the TV screen, which would negatively impact
| contrast.
| mlyle wrote:
| No. It's not literally infinite contrast.
|
| On the other hand, there's very little light spill from
| DLP--- and what little there is, is attenuated by a really
| big factor by the LCD.
|
| I'd guess the limiting factor is light scattered elsewhere
| in the room and by the front surface of the display.
| gibibit wrote:
| Ignoring the fact that the projector doesn't get to true
| black (noted by smusamashah), and supposing there's no
| diffusion that spreads the light of a pixel out to
| surrounding areas of the display panel, it would be possible
| to say that the display has infinite contrast, I suppose that
| is true.
|
| Contrast is important, but alone it is useless. You could
| have a display with only two levels: black and white, and if
| the black is perfectly black, then it's infinite contrast
| (any level of white, no matter how dim, is infinitely
| brighter than total black), but 1-bit color would be useless
| in reality for home theater.
|
| To make infinite contrast useful, it's necessary to have HDR
| as well to take advantage of having very dark and very bright
| areas both able to be represented with detail. Plus having
| sufficiently bright maximum brightness so that the brightest
| highlights can really shine.
| deepsun wrote:
| Just to note that absolute black is not achievable. The
| best coatings in labs reach 99.99% but it's never 100%.
| theshackleford wrote:
| > To make infinite contrast useful, it's necessary to have
| HDR as well to take advantage of having very dark and very
| bright areas both able to be represented with detail.
|
| SDR benefits incredibly as well. HDR is another elevation.
|
| Getting stuck with LCD contrast for years was a travesty to
| image quality across the board.
| SirMaster wrote:
| That's not true at all. Black on a projector is still
| projected light, especially with a DLP which have the worst
| contrast ratios of the 3 projector types (DLP, LCD, LCoS).
|
| What he is making here is a dual panel display. There are
| actually some LCD monitors that use this concept of 2
| separate panel layers each providing their normal contrast
| resulting in a multiplicative effect.
|
| For the video posted here, the DLP is probably at best 1000:1
| and the cheap old LCD is also maybe about 1000:1, so you get
| about 1 million:1 which is a lot, but not technically
| infinite like self-emissive display that can turn off the
| pixels completely for sections of the picture like OLED and
| microLED.
| Dylan16807 wrote:
| What makes self-emissive "technically infinite" but not
| DLP?
|
| I would say the weak point of DLP is the screen material
| needing to be light-friendly, but that's on a sliding scale
| with the emissive display, not a hard line difference. Both
| of them preserve black levels when turning on, unlike
| traditional LCD, but also it isn't true black for either of
| them.
| SirMaster wrote:
| LCD projectors do better at contrast than DLP though.
|
| For example the Epson 5050UB or LS12000 do about 5000:1
| native contrast. Most DLPs around the same price level
| are in the 1000:1 to at most 2000:1 contrast level.
|
| A DLP is nothing like an emissive display. The entire
| area of a projected image with any projector is always
| lit up by the light source. Any projector, including DLP
| is like a TV with a single backlight and no local array
| dimming.
|
| Here are some simple photos of DLP projectors and here
| you will clearly see that the black parts, like the black
| bars above and below the cinemascope image, or even the
| spill over past the edges of the panel are not black at
| all.
|
| https://i.redd.it/ak3lwsumvccc1.jpeg
|
| https://preview.redd.it/eyc62402amnd1.jpg?width=4000&form
| at=...
|
| In that second photo, the odd shape of the black
| projected area is due to the user using keystone, so the
| image is not being displayed on that part of the imaging
| panel and it's just left black, but you can see then what
| the black level really is for projected "black" pixels.
| tshaddox wrote:
| > Black on a projector is still projected light, especially
| with a DLP which have the worst contrast ratios of the 3
| projector types (DLP, LCD, LCoS).
|
| If DLP has worst contrast than LCD, then why would this
| project be even remotely successful? Wouldn't the LCD layer
| in the stock LCD TV would have already been more
| effectively blocking the light from the stock backlight?
| Miraste wrote:
| You're missing that the LCD is still there. It's still
| blocking just as much light as it originally did, but now
| the DLP chip is also blocking light. The effect stacks.
| tshaddox wrote:
| I suppose so, but is that fundamentally different from
| just putting two LCD layers (from two identical TV) in
| front of the backlight?
| SirMaster wrote:
| No and there are monitors that do that (search dual layer
| lcd monitor). They are really expensive.
| drjasonharrison wrote:
| The projector lens's optics (coatings, materials, etc.) will
| have been designed and engineered to have a specified
| contrast ratio.
|
| So yes, if the internal light engine of the DLP truly
| reflected all light away, then, if it outputs zero photons
| for full-screen black, you could say the projector outputs
| zero photons.
|
| However, the DLP is not 100% effective; the interesting
| images will have a mix of bright and dark areas, and the lens
| and software image processing will raise the black levels
| above zero.
|
| Source: I worked at BrightSide Technologies before and after
| the acquisition by Dolby Laboratories and learned about DLP
| lens limitations from the engineer working on DLP+LCD based
| HDR displays.
| smusamashah wrote:
| When I read infinity contrast, and knowing how great DIY perks
| is, I assumed it to be something like this
| https://youtu.be/JoLEIiza9Bc?t=335 but couldn't wrap my head
| around the idea on a TV.
| numpad0 wrote:
| the joke is that contrast is a ratio, and any number over zero*
| equals +inf. I've seen similar lines used in OLED
| advertisements during 2010s, despite many OLED having non-zero
| minimum intensity. It's a reference to those.
| Animats wrote:
| Projectors are only "infinity contrast" in total darkness.
|
| But with enough lamp power...
|
| Larry Ellison used to have a TV projector sized for a movie
| theater but aimed at a home sized screen, so he could watch
| movies and enjoy a view of the outside world at the same time.
| Of course, now anybody can go to Costco and buy a TV that
| bright.
| SirMaster wrote:
| Projectors are never infinity contrast as they cannot turn
| off individual pixels. Projectors have a single constant
| light source to all pixels like a non local-array dimming TV.
| It's entirely up to the imaging panel to modulate the pixels,
| and none of the 3 panel types can block all the light for a
| pixel.
| firefoxd wrote:
| I'm glad he is back to making approachable projects. It was a
| boon for me during the pandemic. I particularly love the fake
| windows to light my closet that looks like daylight.
| PhunkyPhil wrote:
| Is that one really doable?
|
| It's one of the ones that's been at the top of my list, but my
| lack of engineering/tinkering experience has made me a bit
| apprehensive. Is it result really worth the effort?
| all2 wrote:
| There's 3 components:
|
| 1. a TV or monitor diffuser
|
| 2. a sheet of LEDs
|
| 3. a power supply capable of driving those LEDs. Typically a
| 12V supply is sufficient (I don't recall if he goes into
| power supply sizing).
|
| If you're comfortable with learning some things (soldering in
| this case), you'll be able to pull this off pretty easily.
| Uehreka wrote:
| My friend and I looked into that one to see if it would help
| his mood when working in his downstairs office (his apartment
| had a weird layout upstairs). It kind of looks like you need to
| have a room you can sacrifice to hold all of the equipment, and
| a door with the right shape. It wasn't very practical in that
| apartment, or in any apartment either of us have lived in
| since.
| ThrowawayTestr wrote:
| The results he's able to achieve with this are very impressive. I
| wonder if consumers would accept a TV that isn't paper thin if it
| had OLED performance at LCD prices.
| anadem wrote:
| Nice, but he totally hides the lining-up of the rear projector
| image with the main screen's image, which I imagine is a painful
| process.
| laweijfmvo wrote:
| he talks about that extensively and goes over the software
| fix(es)
| KeplerBoy wrote:
| meh, he doesn't really address the issue. He just mentions
| using OBS to threshold the image and dilate the resulting
| regions.
|
| That raises a lot of other questions: He obviously feeds two
| different videos to the displays. How is this done? Does it
| add latency, does it work with, let's say, Netflix DRM? Are
| the two videos even in sync or is the obs post processed feed
| always N frames behind (think of the transition between
| barely lit and bright scenes)?
| badmintonbaseba wrote:
| I would be more interested in matching up timing/latency,
| especially with the OBS processing in the middle.
| drjasonharrison wrote:
| and don't forget to re-synchronize the audio!
| uSoldering wrote:
| I think it's odd to make a whole video about a DIY rear-
| projection television without using the phrase 'rear-projection
| television'. It's novel to bounce it off the ceiling, and it
| repurposes e-waste so it's a great project.
| tobr wrote:
| He does mention rear-projection TVs.
| uSoldering wrote:
| I guess I missed it and was hoping for a deeper dive.
| Miraste wrote:
| The novel part is projecting onto an LCD panel instead of a
| simple piece of glass.
| withinrafael wrote:
| Very cool and a great speaker. Forgive my naivete but would
| enclosing the back with a short-throw projector reintroduce the
| LCD light bleed he fought hard to eliminate? I wonder how you
| would address that. I suspect painting the interior Ventablack
| wouldn't be enough.
| ChrisMarshallNY wrote:
| Very cool, and great video.
|
| It seems that projector tech (like laser printer tech, and
| flatbed scanner tech) has been pretty stagnant, the last few
| years.
|
| Every now and then, I look at the latest projectors, to see if
| there's any justification for me to replace my old (10 years or
| so) LED projector, and I have not seen anything that has made me
| want to.
| Miraste wrote:
| They have gotten better. Recent consumer projectors use triple
| (RGB) lasers as a light source, which improves color accuracy a
| lot. It's not worth replacing one that works, but it is
| noticeable.
| ChrisMarshallNY wrote:
| My experience with laser projectors, is that they work great,
| but have very weak beams (for reasonably portable ones).
|
| I need it to be something I can toss into a backpack (along
| with a bunch of other stuff), and be around 1000 lumens.
|
| Not just lumens, either. The color needs to be good, the
| resolution needs to be (hopefully) greater than 1080p, and it
| needs to be usable in a semi-lit room. I don't care about
| speakers. I use projectors as a speaking aid.
|
| I've been using a tiny InFocus LCD unit that's great, but a
| little anemic (1080p/750 lumens).
|
| The promise of a laser, is that you can project it against a
| cinder-block wall, and it will stay in focus, and show great
| color.
| Miraste wrote:
| I've only used larger, higher power ones that are meant to
| stay in one place. Even with those, all the "point it at a
| wall and it looks like a TV" marketing is fiction. They
| don't look good without projector screens unless you're in
| a dark environment.
| ChrisMarshallNY wrote:
| Makes sense.
|
| I have heard that laser projectors don't need to be
| focused.
|
| Is that true?
| Miraste wrote:
| Yes and no, but mostly no. Nearly everything advertised
| as a laser projector uses the laser as a light source for
| a normal DLP/LCD/LCoS setup, and needs to be focused the
| same as with a light bulb source. Even the triple laser
| ones work this way-the triple laser part just means they
| don't need a color wheel.
|
| There _are_ true laser projectors where the lasers go
| directly to the projection surface. These are called
| Laser Beam Scanning projectors, and they don 't have to
| be focused. They work pixel by pixel in scanlines kind of
| like a CRT, and since the laser doesn't diffuse over
| short distances, it's never blurry.
|
| Unfortunately, it's a dead technology. I only know of one
| still in production, and it's 120lm or something.
| SirMaster wrote:
| They improve color gamut coverage and color volume, but I
| would not say accuracy. It's much harder to get an RGB laser
| projector accurately calibrated than an old mercury lamp or
| even single blue laser / yellow phosphor projector.
| abdullahkhalids wrote:
| For the sake of my eyes, I have wanted to switch from using a
| secondary computer monitor to a projector. I imaging switching
| looking from primary monitor at 2 feet vs projector screen at 8
| feet would be good exercise for the eyes.
| ge96 wrote:
| I like this super low F-stop lens video although it was massive
| WWLink wrote:
| Hahaha I guess it's time to bring back rear projection TVs!
| kridsdale1 wrote:
| This is an old concept. There was a research lab in Vancouver
| circa 2008 who did exactly the same thing (I applied to intern
| there as an EE student). It was the first HDR video display ever
| built. They had to also design the encoding format.
|
| They never commercialized but they sold their patents to Dolby
| who turned it in to "Dolby Vision".
| gedy wrote:
| I saw similar at SIGGRAPH 2004. Still a cool DIY project.
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