so im startin to build my projector and im lookin through the archives to find the lens to use.. and the most common amongst psone projects (concerning me as im using a psone lcd) is the delta lens.. which is now unavailable.

so what are my alternatives? i have found a few differant lenses that i think would be suitable but im not totally sure.. people often refer to using a "tv" lens.. i have found many tv lenses but im not sure if im looking at the right sort of thing and none of them ever state the focal length,,

this is something i have found on ebay but im not sure about it...

http://cgi.ebay.co.uk/TRIPLET-LENS-VARIOUS...%3A1|240%3A1318

if anyone can give me any advice it would be very much appreciated

and any advice into fresnal size and lamp size etc as well.... i have several metal halide lamps at home already from other ventures long since past ranging from 150w up to 6oow and it would be good to put them to some use

thanks guys

Sure, you can use that triplet.
You can buy the S15 Fresnels (220mm & 317mm - cut to size) and try one of your 150W MH lamps.

It's been shown that you don't want to project larger than 60" with a PSOne screen, as it'll look too pixelated.

An unsplit setup would look like this:


And a split setup would look like this:


Check out the following Google search for more PSOne/OHP builds: site:lumenlab.com +psone +ohp

You might run across a "quirk" when searching using Google, however. If you notice the thread looking "wonky" like this image, simply go up the the top right corner of the thread and click on Options and then Switch to: Standard.

oh cool thanks i was having trouble using the focal calc. as i run linux ubuntu and hate using wine.. the old one works well but i find that visual imagery is very helpful

ideally i want the projector itself to be as small as possible.. and i notice that the throw distance there is 13 feet which is quite a bit more space than i have to work with.. all the other variables seem very good though.. a 60" screen would be great!!

can anyone give me any advice on what i would need to achieve as big an image with a shorter throw? and would it be foolish to use a 400w mh lamp cos of the heat it puts off (i dont wanna burn my house down...)

thanks guys

How short of a throw were you looking for?

well i live in a room that is probably about 13ft x 13ft so i would need a throw to accomodate that.. i worked something out on the focal calc that gave me a 60" screen with a 5ft throw but my numbers were not very exact in relation to things i have found ie fresnal and triplets etc...

im using my windows pc today and using the visual focal calc seems to be easier for me.. i will do some more sums

cheers mate

ok cool i have got a bit further now using the focal calc

i have found these setups to be quite good?





here are the lenses i have found on surplus shed

http://www.surplusshed.com/shop/basket.cfm

and this fresnal http://cgi.ebay.co.uk/FULL-Page-Sheet-Magn...%3A1|240%3A1318


my question is this.. will this work? it all seems to be fine by my reckoning...?

and also.. what about the rear fresnal? is this important?

thankkkyouuuu

The link from surplusshed goes to shopping basket unless we have your account info we cant see it...

hmmmm... that is correct... sorry

here are the lenses

http://www.surplusshed.com/pages/item/l3604.html

http://www.surplusshed.com/pages/item/l10148.html

http://www.surplusshed.com/pages/item/l3465.html

thanks very much

A 4.5' or 5' throw is incredibly short.
You have to keep in mind that, if you're building a split setup, you'll only be able to keystone to a maximum of 15 degrees - and probably not even that much. If you build an unsplit setup, your projector will have to be perpendicular to the center of your screen.
Before you even start to build, you might want to throw together a mock-up out of cardboard (like John D did) and that will give you an idea of whether or not the projector will block your view of the screen.

hmmm.. yeah i see what you mean now.. it will have to be fairly central.. im sorry for sounding so much of a noob but which part of the system is the keystone? and how is it to be adjusted..? at a guess i would say it is the front fresnal.. and that by tilting it slightly it changes the throw of light through the lens so that the projector could be placed lower than the screen?

i really dont have much room to work with so i guess this is pretty important....

cheers

Keystone Correction

There is also lens shifting, but it's a bit more complicated.

ok its all good.. i bought a lens of surplus shed which has focal length of 4-6 inches so i figure if i can get it at 6" combined with my 300mm front fresnal then it should give me and more healthy throw at 60 inches.

im still confused about the first fresnal.. the collimating? i mean.. what does the focal length have to be? im using a psone screen.. shall i just buy another 300mm fresnal and use that?

sorry for bein a noob but its got me stumped

cheers

The first fres. focal length is from the light bulb to the fres. a 220mm focal length is the ideal for optimum brightness 330 tends to loose brightness.

ok cool.. 220 is what i had read for most of them but i was not sure if that varied when the size of the screen changed..

so i need a first fresnal of 220mm definately to catch the light yes?

cheers

yep

Actually, with a 5" screen, you want the first fresnel FL to be as short as possible. If you can find one that's 100mm or shorter and will still cover your entire PSOne screen, then I'd say go for it. The shorter that you can make that collimator (Within reason, given the LCD size) the brighter your projector will be.

ahhh that sounds cool.. i will begin hunting for a well short focal length fresnel then.. any advice on where to start looking anyone?

i have got everything else sorted now so i may just begin building with what i have and see how it goes....

thanks very much guys

You can find some 220mm fresnels as well as a 210mm triplet at izzotek. They're located in France.
If you do a Google search for "180mm FL Triplet Lens" (in quotes), you'll find that triplet sourced in the US. On that vendor's page, you'll also find recommendations for 180mm fresnels.

Sorry, we can't provide links to competitor's websites.