Diaphragm (optics) curved blades improve the roundness of the iris opening. In a photograph, the number of blades that the iris diaphragm has can be guessed by counting the number of diffraction spikes converging from a light source or bright reflection. For an odd number of blades, there are twice as many spikes as there are blades. In case of an even number of blades, the two spikes per blade will overlap each other, so the number of spikes visible will be the number of blades in the diaphragm used. This is most apparent in pictures taken in the dark with small
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