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Author Topic: fresnel lens big screen tv  (Read 2249 times)

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eightbit

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fresnel lens big screen tv
« on: March 19, 2003, 11:07:56 am »
Has anyone tried the big screen projection tv off from ebay?
Heres an example auction-
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3012024832&category=20389

I'm doubtfull about how well it works for viewing in a big room but I was thinking about trying it inside of a sit down cabinet that would be mostly enclosed.
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Re:fresnel lens big screen tv
« Reply #1 on: March 19, 2003, 01:13:08 pm »
if it was that great people would alreadybe using them everywhere...universities, bars, etc...
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rampy

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Re:fresnel lens big screen tv
« Reply #2 on: March 19, 2003, 01:29:35 pm »
well i'm sure there are drawbacks... but someone in byoac DID use a fresnel lens with their project to make their 14" pc monitor look less tiny in the cabinet...  *shrug* ymmv...

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Re:fresnel lens big screen tv
« Reply #3 on: March 19, 2003, 01:41:33 pm »
i actually got a fresnel lens and gave it a go (just using a mock-up made out of card) and it works ok...

my image wasn't that bright (i was using an old 15" monitor though), but it was quite sharp

i reckon it'd work quite well if you used a tv with the brightness+contrast turned way up

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MameFan

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Re:fresnel lens big screen tv
« Reply #4 on: March 19, 2003, 03:33:32 pm »
I think I posted here before about my experience with one.

I found one in original box that looked like it came from the late 60's or early 70's at the latest (style of print, pictures of people/tv set's of the time), therefore the newer lenses MAY likely be better.

It works as advertized, but with large pixel, high contrast graphics  (especially of older "classic" games) as compared with smooth image TV pictures, you will clearly notice what I call "warp speed light traces" appear between the lens and the CRT.

Better explained, here's an example:

In the attract mode of Ms.Pacman, the ghosts come in from the right side of the screen and go under the rectangular logo and slide up the left side.   When watched through the lens, each ghost will have it's color in a dimmed fashion appear to be a ghost line drawn towards the center of the screen, sort of how it looks in star trek when they go to warp speed and you can see the traces of light go diagonally towards the center of the screen.

In addition, unless you are EXACTLY standing in the center, you will notice geometric distortion of the edges of the screen farthest from you.


Again, this was with a ~30 year old lens meant to enlarge old 15 and 17 inch TV tubes to look like 30" ones, so newer tech may work.  At the very least I'd suggest putting it behind the smoked plexiglass to reduce seeing some of the issues with them.