Does anyone know how to make an Overhead Projector?

Hi All, does anyone know how to make an OHP (just to be clear "OHP" not "OAP" - I already have a couple of these and despite their age they work perfectly well). i'm no artist (nor nuffink), but i'd like to paint an intricate image onto a large canvas. i've mocked the image up on paper, but to ensure accuracy, i'd like to project this image on to the canvas and trace from that. i'm unable to link my computer to an OHP device for all sorts of dull reasons (that neither you, nor i would want to go into right now), so unfortunately this isnt an option. all (practical) ideas will be gratefully received. regards Rens

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jbath5 years ago
Do what Leonardo Da Vinci had to do.

First divide your drawing into four quarters and reproduce each quarter by squaring off the original and enlarging it four times on to the respective quarter of your larger paper. Then pin prick all over the lines of your blown up reproduction and with a pencil transfer your pinpricks four times larger, on to the wall by poking the tip of the pencil through each pinprick. then join the dots on your new four times larger surface.

Squaring off means covering your drawing with vertical and horizontal lines then doing the same on a blank sheet but with four times (or however large you want to make it) the distance between the lines.
Goodhart7 years ago
lemonie9 years ago
A bright light, lenses and a mirror would be required.
I was looking for a nice diagram of one for you, but got distracted by this:

your link there is worrisome - I wouldn't want the general public to have access to my 'to do' list at work....
rens (author) 9 years ago
thanks for all your suggestions...i think the best idea (assuming it's not feasible / affordable to make my own OHP)is to try and loan one from a school...better get moving quick as they'll be closing for summer soon ("summer"!?! given the weather in the UK this term is surely in violation of the trades description act...if anyone happens to be speaking to the almighty one over the next couple of days, could you mention it on my behalf?) shame about the OHP...i was looking forward to the prospect of toiling away on this...guess not everying in life is Instructablisable.
Kiteman9 years ago
If your "master" is on paper, you don't need an OHP, you need some kind of camera obscura or camera lucida.

The obscura uses a lens to project an image in a large box or room (like a giant pinhole camera. Put your canvas on the "wall" of the box and brightly-illuminate your master opposite the lens.

The lucida uses mirrors to overlay the image of your master over your view of your canvas. All you need to do is trace around what you see.
rens (author)  Kiteman9 years ago
sorry to be a dullard, but does this work even when the image I'm starting from is smaller than what I'd like to scale it up to? i.e - the mock up is probably 1/4 of the final size.
Kiteman rens9 years ago
The obscura would, you just arrange canvas, lens and master to match what you want, but the lucida wouldn't.


Most obscura are smaller than what the artist wishes to portray, but there is no scientific reason why.
rens (author)  Kiteman9 years ago
sheeeshkebabs!! I will need a really large mirror, glass panel & box to do this as the final canvas size is 720 x 1680mm (assuming i haven't misunderstood the useful link you sent) I'm kinda hoping that i have misunderstood something, as i'd like to give it a go, but before i do...given the canvas size (720 x 1680mm), will i need to scale up the materials accordingly? many thanks for your help on this one.
Kiteman rens9 years ago
The box can be a room or tent... ... actually, thinking about it, it would be easiest to re-draw the image onto an acetate sheet and then borrow a projector from a local school's art department.
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