Gigantic 100" Projector Lens

[Shamone MO FO]

Firstly apologies in advance if I have posted this in the wrong topic!

Now I have just been looking at a lens on ebay that claims you can use it with a portable (14") TV and project that image of upto 100" onto a wall.
Now I am a bit sceptical about this
The guy is a power seller and has quite a few good comments but who's to say that his mates haven't just posted these (see waht I mean about sceptical) LOL

Has anyone ever done this or know a man who has? Even your view would be welcomed on this one!!

The Lens is only £3.75 GBP but the moneys not the issue - I dont want to waste hours of my time constructing the thing to find I'm the latest sucker falling for a Scam!
You can see for yourself the item is here: http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=3375639644&category=32046

I look forward to all those replies! Lol

[offline]

Never seen one but think about the pitch. 14 inches to 100 inches = lots of big blurry dots. You would have to sit a fair distance away in a pitch black room and have a bottle of asprin handy.

[Shamone MO FO]

That was my first view but if you look at the link the picture quality (on the wall ) looks pretty good!

The jury's still out

[NightWing]

These thing have been around since the dawn of tv.

Problem are a few physic laws that relagate this to pitch black rooms or burning out the source to get enough light to even project it.

There are good reasons why those projectors cost so much.

[Cobra]

I was just thinking about that: how bright would you have to set the poor little TV to get decent brightness over that area?! If you see a projector (even an overhead projector in schools) the bulbs they use are extremely bright - sometimes even metal halide lamps (hence the fans to cool them down).

There's a rat in a blender's chance that this lens will do anything but project a blurry, dark mass onto a wall. Not worth it unless you feel like buying it and getting legal about it being a hunk o' junk. You'd need a lot of spare time, though!

CobraDMX

EDIT: And anyway, if these really worked you'd be able to buy them in the high street. You can't though. Also, I notice the guy who wrote that advert can't spell.....

[Shamone MO FO]

Hmmmm put very well now you come to think of it!

Yeah I think I'll save my time. DAMN if only I could afford a REAL Projector! ah well there's always a 100W bulb and a magnifying glass! maybe I will sell my idea on ebay- Probably work just aswell as those ones LOL

Thanks anyway guys!

[Cobra]

Anything, if marketed correctly, will sell. Just look at McDonald's!

CobraDMX

[BJ_M]

Never seen one but think about the pitch. 14 inches to 100 inches = lots of big blurry dots. You would have to sit a fair distance away in a pitch black room and have a bottle of asprin handy.

in reality all CRT based video projectors and rear view monitors use anywhere from a 3" - 9" CRT which is blown up to even ~16 (lcd and DLP projectors are a lot brighter and go bigger) screen ..

but these are VERY high output crt's with lots of cooling (sometimes even water based cooling) ...

as mentioned -- his contraption has been around since the dawn of tv . i remember seeing these sold in the 60's ..

didnt work then either ...

[offline]

in reality all CRT based video projectors and rear view monitors use anywhere from a 3" - 9" CRT which is blown up to even ~16

1st of all, cathode ray based projectors are terrible. This was the
first technology to be seen in consumer rear projection units - dark, blurry and washed out images. 2nd, even the earliest units had to have
a special CRT with much finer pitch, higher contrast and brightness than an ordinary TV screen - some models having three screens to handle
each primary colour and improve output (kind of an early elcheapo RGB system.) Now imagine the results with a standard 14" TV ?

(lcd and DLP projectors are a lot brighter and go bigger) screen ..

Sure, but what has that got to do with this thread?

[doctor]

There are free plans on the net to make one of these using a fresnel (sp?) lens & plywood, or even cardboard, if I remember correctly. Might want to look at that before you go any further.

one of them is here:
http://bigscreentv.20m.com/photo.html

[BJ_M]

in reality all CRT based video projectors and rear view monitors use anywhere from a 3" - 9" CRT which is blown up to even ~16

1st of all, cathode ray based projectors are terrible. This was the
first technology to be seen in consumer rear projection units - dark, blurry and washed out images. 2nd, even the earliest units had to have
a special CRT with much finer pitch, higher contrast and brightness than an ordinary TV screen - some models having three screens to handle
each primary colour and improve output (kind of an early elcheapo RGB system.) Now imagine the results with a standard 14" TV ? :x

(lcd and DLP projectors are a lot brighter and go bigger) screen ..

Sure, but what has that got to do with this thread? :?

i guess you have never seen a good quality CRT projection system ... they are stunning quality ... they all use 3 tubes .... red green and blue.

Red green and blue are additive primary colors ...

the true primary colors are red , yellow and blue .. also,

Magenta, yellow and cyan are process primary colors.

i brought up dlp and lcd projectors becuase i had qualified the crt projector as being up to a 16' screen more or less .. video projectors can go on a larger screen of course but not crt based systems - so i qualified my statement ...

there is one exception though to a larger than 16 foot crt based projection ... JVC/HUGHS video projectors at one time used crt's in thier video projectors which through a secondary proccess were blown up to even ~40+ foot screens ... They competed against the GE talaria which used oil instead of a tube to form the video image and were a little brighter but you could not tip them at any time more than 30degree's or it would be a 25,000$ repair bill each time (the projectors cost $250,000)..

[robb7979]

Shamone,
I've only read one "un-biased" review of these lenses on the internet, and I just can't remember where it was. I think it was on the video section of www.diyaudio.com, not sure. Anyway, whoever it was said that it worked, but barely. The tv just wasn't bright enough. Also fresnal lenses aren't designed for projection, so you can imagine the crappy quality. Incidently, if you'd like to see one of these lenses anyway, you can buy them at pretty much any drugstore. They're called page magnifiers. You can get a good projector below $1000 nowadays anyway

-rob

[mikel]

quote:
"They competed against the GE talaria which used oil instead of a tube to form the video image and were a little brighter but you could not tip them at any time more than 30degree's or it would be a 25,000$ repair bill each time (the projectors cost $250,000).."


A used Taleria is much cheaper these days. They are a pain to move.
(VERY HEAVY)
Mine is about 1/3 the size of a refrigerator. Older light-valve technology, still a good picture though, (maybe up to 25ft max) , but it takes about 45min for the oil to heat up, so ya gotta plan your viewing in advance.

[offline]

BJ_M,

you are confused I believe. We are discussing a tv screen in a box
with a lens - NOT a separated RGB projector. Some had 1 screen
and were B&W, some had 3 screens RGB. Early models used just
a lens, others used mirrors and ant-reflective coating with a
secondary light source.

Nothing you said refutes my argument, some of it
seems spurious. What has oil based 40 foot images and DLP/LCD
screen sizes got to do with it? BTW it is not incorrect to state
that red,green,blue are primary colors in this discussion- they are primary for pixels. While the video signal can transmitted in
component form to improve the image, how many or rather
what are the primary colors of the pixel? Answer: Red, Green, Blue.
Calling RGB "additive primary" is just semantics in my book.

[BJ_M]

quote:
"They competed against the GE talaria which used oil instead of a tube to form the video image and were a little brighter but you could not tip them at any time more than 30degree's or it would be a 25,000$ repair bill each time (the projectors cost $250,000).."


A used Taleria is much cheaper these days. They are a pain to move.
(VERY HEAVY)
Mine is about 1/3 the size of a refrigerator. Older light-valve technology, still a good picture though, (maybe up to 25ft max) , but it takes about 45min for the oil to heat up, so ya gotta plan your viewing in advance.

a really neat machine ... we had something like 6 of them at one time.. does yours have the rainbow effect around the picture ? I wonder where you could even get one of these fixed ... i guess there would be a number of these around along with edophores and hughs and the like (can't remember all of them) ..

GE made a double model of the talaria for 40+ screen - it WAS the size of a fridge .... it also had a better picture ....

[mikel]

Yup, it has the colors around the frame of the picture..
The original buyer gave up on it. (could not afford to fix it)
...it passed thru a couple other hands till I got it for free.
And lucky for me, after messing around with it for more than a few hours,
I got it up & working.
It came with a long lens....might be fun to project movies on the
garage door across the street.
mikel

[unloaded]

Here's another way to make DIY projector. This method actually does fairly decent and can be done for pretty cheap.
http://www.gideontech.com/guides/projector

peace.
unloaded