Use the same tube to trace a circle on a thin sheet of aluminium.(A flattened out drink can works well although thin black card will also work).Initiate the slide show and point the projector a few feet away from the flysheet of your tent till you get a 'sharp' image. Measure the window then cut out, (or stick together) some light tight material (cardboard or black plastic) to a size a bit larger than the window.
After scouring cheap shops the best items I have found, and a healthy balance between transparent and opaque, are thin dust sheets and plain white shower curtains, both of which can be found in the same pound shop you got your lenses from (sorry, should have told you earlier! These are then placed into the obscura or hung from the celing.
With care they can also be laminated to make a flat screen (although the shower curtain material sometimes melts!
Look through with one eye whilst blocking the excess light with your hands.esigns incorporate a single element lens rather than a pinhole.
The increased brightness of a lens means these obscuras can be used in most light conditions.
) Another option to entertain the class would be to make 11 cameras, strap them onto the school football team and watch them try and play football against a group of Y7s whilst viewing the world upside down.
Probably get done on health and safety grounds but worth a giggle!Theses obscuras can also be part of a cross curriculum projects incorporating art, design and technology, recycling, science, (even PE!) Below are some examples from the vey wonderful Trinity Catholic High School in Essex. When you are bored of scaring each other with ghost stories, go to 'settings', disable the 'auto- rotate screen', set up your phone to 'video' or photos on 'slide show' mode and fix the phone under the rubber bands upside down (the image is inverted).) Take the lid off a shoebox and cut two holes at each end, one oval or rectangular (wide enough for both eyes to see through), the other circular and the size of your magnifying glass.(It sometimes takes quite a bit of scissor work to cut through the card!The earliest form of 'photography' and use of a pinhole was the camera obscura (latin for 'better than the telly').