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Hello, my name is Judas Gutenberg and this is my blaag (pronounced as you would the vomit noise "hyroop-bleuach").



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   how best to project a design onto a painting
Thursday, November 29 2012
My most recent painting was based on a photograph. Ideally I would have been able to somehow project an image of that photograph onto the canvas and use that to sketch out the rough composition. But because I had no way to do that, I ended up resorting to the ancient technique of working to a grid. Mind you, I have a device called a Project-A-Scope (it's nearly as ancient as the grid technique) stolen from my mother that supposedly uses reflected light to project an image from a flat opaque object onto a wall, but the image it casts is too dim to be useful. I'd had plans to build my own VGA projector using an old laptop and an overhead projector, but the other day when I did a quickie-build on such a device, I ran into a number of problems. For starters, it's impossible to remove all the wiring and guts from behind most laptop LCDs. You can get rid of the diffuse light source with its layers of fresnel-lens plastic, but the wiring connecting the LCD elements to their control circuitry usually attaches along two edges of the display with wires that are too short to permit get the electronics out of the way so that light from a bulky source (such as an overhead projector) can shine through unhindered. In theory a laptop-cum-overhead-projector should work great, and in practice it is much better than a Project-A-Scope, but it's a clunky, unweildy system, and then there are those shadows from the electronics that cannot be pushed out of the way.
So today I took delivery of an NEC MT820, a genuine SVGA projector I'd bought on Ebay for almost $90 (including shipping). That's a good deal and was one of the few times I'd actually done anything other than click "buy it now" on Ebay. I'd been outbid on a 1280 by 1024 pixel projector that had gone for about $120, so I'd been determined to get this 800 by 600 pixel unit.
Today it arrived, a big boat anchor of late-90s technology, dating to when LCD projectors were rare and expensive. As had been mentioned in its Ebay description, the only thing wrong with it was that its zoom functionality was inoperable. I immediately took the projector apart and soon had isolated the part that wasn't working. A plastic gear on a small servo motor was spinning uselessly on its plastic shaft. If only more friction could be developed in that mechanical connection, I could get zoom working again. At first I tried SuperGlue, but that didn't seem to work (and there was a real risk of accidentally getting glue into places it should definitely never go). So then I tried welding the plastic gear to its plastic shaft. This was easier to do than it sounds; all I had to do was heat up the tip of a tiny screwdriver and then use it to poke the junction between the gear and the shaft in a couple places. To ensure a good connection, I didn't just poke; I also twisted. The fix worked and now my projector has zoom. The resolution isn't great, but it should be adequate for sketching out overall composition. And with the zoom functionality, it should also be possible to project higher-resolution details onto details of a painting as needed.


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http://asecular.com/blog.php?121129

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