Ross, Andrew & Thomas. The advent of collodion negatives on glass in the 1850s made enlargement more practical. Achille Quinet's invention of 1852 used artificial light, but was inefficient, requiring very extended exposures. David Acheson Woodward's 1857 'solar enlarging camera' addressed that problem by tapping the brightest light-source then available – the Sun – with mirrors and a condenser. Solar camera Solar cameras, introduced in the late 1850s, and ancestors of the darkroom enlarger, were necessary because of the low light sensitivity of albumen and calotype materials used. A larger version of the 18th century solar microscope, they were first freestanding, a design analogous to picture-taking cameras but with the relative position of negative and lens reversed so that sunlight shone through the glass plate to be projected onto photo-sensitive paper inside the instrument. Mounted on a stand, they could be rotated to continuously face the sun. Woodward's 1857 solar enlarging camera was a large instrument operated out-of-doors that could produce life size prints from quarter plate and half plate negatives with an exposure of about forty-five minutes, improved in the 1860s and 70s with a clockwork heliostat to rotate the mirror in synchronisation with the sun's passage to concentrate its light on the condenser lens, while Désiré van Monckhoven's 1863 patent was for a modification of Woodward's design that had an appearance more like a modern horizontal enlarger. The instrument was used by significant photographers Disderi and Nadar. By 1890, artificial light sources – gas, petroleum, limelight, magnesium, and electric light bulb – were commonly used in enlargers, but even at the turn of the century simple folding daylight enlargers still found a use among amateurs to easily produce prints of a fixed size. Some cameras were made convertible to use in a similar manner. Commercial enlarging In the 1870s hand-coloured enlargements from carte-de-visite prints and daguerreotypes as well as existing negatives were offered for sale in London for two shillings for an A4 print, and three pounds for a life size bust, and R. L. Elliot & Co., of King’s Road could print up to 25" x 20" from quarter plate negatives in 1878 using limelight, as suggested by John Benjamin Dancer. Fast bromide and chloride printing papers largely superseded albumen emulsions in the 1880s. Types of enlarger A condenser enlarger consists of a light source, a condensing lens, a holder for the negative and a projecting lens.