Once the glue has dried, cut your crisp can to length. The longer the tube, the greater the magnification, but the more light will be lost (requiring a longer shutter speed or higher ISO).
With your tube cut to size, it’s time to mount your lens.
A 50mm prime lens is ideal, and as you aren’t actually ‘mounting’ the lens it doesn’t need to match your camera mount – a manual-focus lens with a manual aperture is ideal – the same lens can also be used for freelensing (see page the Christmas project #1).
Your exposures will have to be set manually and you will have to focus by moving the camera backwards and forwards, but despite these limitations it’s still possible to produce some striking results – you can even turn the lens slightly to create a ‘tilt’ effect.