Instructables

Cardboard Props: How to make a 1950's type Press Camera

Step 5: Lens

Picture of Lens
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If unlike me you do not have a small plastic disk that you can use for a lens you have two options, you can just leave it out as it's not REALLY going to be missed or you can make your own, to do so see below

All i did was drew around a circular shape onto a flat plastic surface like that of a plastic tub, and cut out the shape using a sharp knife (or pair of scissors depending on your preference)