Human eye The upper end of the range is given in terms of normal visual performance as 10 cd/m (100,000,000 or one hundred million candelas per square meter). The eye includes a lens similar to lenses found in optical instruments such as cameras and the same physics principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop. Refraction in the cornea causes the effective aperture (the entrance pupil) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it
The Flower of Gloster The Flower of Gloster The Flower of Gloster is a 1911 book by E. Temple Thurston (23 September 1879 – 19 March 1933), an Anglo-Irish poet, playwright and author. Published by Williams and Norgate, it sold well enough to merit a second edition two years later. A third unillustrated edition was published by Chapman and Hall in 1918, after which the book remained out of print for over half a century until being republished by David & Charles in 1968. A year before that, ITV had broadcast a 13-part children's serial of the same name (loosely) based on Thurston's original