Homemade movie screen for someone who's not 100% clear on aspect ratio

August 3, 2023 12:51 PM

Making a DIY indoor screen to project stuff onto extremely basic: cardboard tubes, fabric, staple gun. The best place to hang it will accommodate about 65" of width. For most things I'm going to project from Netflix or wherever, how many inches top to bottom should I be figuring on? I feel like there's a very basic answer here but it's the kind of thing I google and people are talking about it in depth and my eyes glaze over...
posted by less-of-course to Media & Arts (10 answers total)

Best answer: It should be the same aspect ratio as whatever your projector is, typically 16:9. That's about 1.78. So if you want 65 inches wide, you want 36.5" high. 65/36.5 = 1.78 (approximately).
posted by wnissen at 12:57 PM on August 3, 2023 [7 favorites]

try a calculator like this.
netflix is mostly a 16:9 ratio, to calculate screen size you should input the distance folks will be from the screen and the calculator will output the dimensions.
posted by dannysaur at 12:58 PM on August 3, 2023 [2 favorites]

Cinematic programming these days will be mostly 16:9 but there is a fair amount of produced-for-television content or older movies in "full screen" (as opposed to "wide screen") aspect ratio that may be 4:3 or thereabouts.

You'll need to decide whether you want your screen to accommodate the latter but if you have 4:3 content to display and your maximum width is going to be 65", then you would want the height of your projection surface to be a bit less than 49". (65 / 4 * 3 = 48.75)

If you don't care about 4:3 content then you can get away with a height of a bit less than 37" (65 / 16 * 9 = 36.56)
posted by Nerd of the North at 1:22 PM on August 3, 2023 [2 favorites]

I think wnissen is right. The dimensions of the screen shouldn't be based on any possible aspect ratios of Netflix movies, or made-for-television productions, or what have you. The dimensions should be based on what the projector outputs. Depending on what you are showing, you may end up with some blank areas on the sides or top of your screen, but that shouldn't matter. You want the screen to accommodate whatever maximum size image the projector can generate.
posted by JD Sockinger at 1:48 PM on August 3, 2023 [7 favorites]

you want 36.5" high

For the viewable part. You may want extra "drop," if you want to install the top bar higher than the top of the image.
posted by snuffleupagus at 2:37 PM on August 3, 2023 [1 favorite]

Nerd of the North is right that you would want the visible area to be 48.75" if you watched a lot of pre-HDTV TV or 50+ year old movies. Depending on your projector, you would need to either zoom it or move it, though.
posted by wnissen at 8:03 PM on August 3, 2023

The PJ (or playback device) will scale SD content and display it with "black bars." If not already scaled in the format delivered (e.g. old movies on a streaming service).

What's going to be connected to playback 4:3 native? A VCR? DVD player? Not a lot of HD PJs with RCA or S-Video inputs (vs. business presentation PJs) — even component is hard to come by now.
posted by snuffleupagus at 5:53 AM on August 4, 2023

Projectors have different "throw distance" which is the distance from the projector to the screen at which it can be in focus. Many projectors have zoom lenses, but on some the zoom is very small (1.1x only).

What this means is that depening on the specific projector, you could find that the location the projector needs to be mounted is inconvenient (e.g. right where your seats are) or impossible (e.g. further away than the back wall).

If you have already have a projector, then set it up and turn it on, focus and angle it properly, then make the screen sized to fit the projected image.
posted by soylent00FF00 at 7:54 AM on August 4, 2023 [4 favorites]

^this is true, and something you can't do with a manufactured screen. (Thus the calculators.)
posted by snuffleupagus at 10:41 AM on August 4, 2023 [1 favorite]

> If you have already have a projector, then set it up and turn it on, focus and angle it properly, then make the screen sized to fit the projected image.

Came to say this. You can guess and calculate and etc etc etc - and those might get you in the right ballpark, especially if done carefully - but there is nothing quite like getting the exact equipment you are planning to use, set up in the exact location you are planning to use it, broadcasting the exact type of content you would like to view (and trying a bunch of different things here - there might be some content formatted differently, or some equipment, say a game console, that requires a different resolution on your projector and so has a different aspect ratio, etc), and then dialing in your build to fit this exactly - and/or, be designed in such a way that it can comfortably deal with any of the possible different combinations or requirements that might be thrown at it.

If you don't have the exact projector/system/etc you are planning to use, personally I would wait to finish the project until I did. It's a sort of "measure twice and cut once" type of situation - once it's all fit and in place, it's going to be a giant pain to make it six inches taller or whatever.
posted by flug at 10:38 PM on August 4, 2023 [1 favorite]