Catriona sewing the curtain for the camera obscura.

The image seen inside the camera obscura, caught on a piece of white foamboard, recorded with a digital camera. The image is roughly 20 x 16 inches. This was recorded with the lens shining down through the maxiumum opening in the roof of the camera, a hole of 6" diameter. This approximates to an aperture of roughly f 4.5.

The mauvey-blue of the cardigan, which is fairly central in the image, shows quite dramatically the spherical aberration of the lens ... right in the centre the colour is quite clean and clear, but move just a small distance away from the centre / axis and the colour rapidly becomes muddier.