274
CAMERAS BY ROSS, KNIGHT, CLAUDET, WILLATTS, &c.
[Ci.ass X.
Careexter and Westley (No. 270, pp. 437, 43S)exhibit a pair of phantasmagoria lanterns; a lantern withthe addition of a microscope, together with a set of lensesto be used in conjunction with them; a series of subjectsin outline, and various paintings adapted for dissolvinglanterns.
IIorne, Thornthwaite, and Wood (No. 220, pp. 434,435) exhibit a dissolving apparatus for the oxyhydrogenlime-light, showing the contrivance for dissolving thepictures; also an oxyhydrogen microscope, and a seriesof paintings for dissolving views. The novelty of thisarrangement consists in the shutters being placed so thatthey cut off the rays where they cross in front of thelenses, by which means a more perfect dissolution takesplace. The quality of the manufacture and the generalarrangement of the various parts are good.
Photographic Cameras.
The camera is the principal instrument of the photo-graphist, as by its means light is made to become achemical agent.
This instrument, the invention of Baptista Porta, to-wards the end of the sixteenth century, was simply adark chamber furnished with a single double-convexlens, fitted in a tube, and serving for the focal adjustment ofthe image. So constructed it was first applied to the copy-ing of different objects, the outlines of which, as given bythe camera, were traced upon the paper by a pencil; butthe image was reversed. After a time this inconveniencewas rectified by the use of a mirror; with an instrumentof this kind, A. Canaletti, at the beginning of theeighteenth century, made the drawings for his fine pic-tures of Venice, winch he consequently executed with aperfection of perspective so great as to be regarded as anillusion.
By degrees a lens concave towards the object andconvex towards the image was adopted; the picture wasthus rendered clearer, but the colours of the spectrumwere not corrected. At length an achromatic lens wasused, the flint glass being towards the object. M. Daguerrewent a step further, and determined those relative pro-portions of the camera, which, for the most part, are stilladopted; the interior being carefully darkened, for thepurpose of avoiding casual reflection upon the field ofview.
Mr. Ross, in addition, prepares those for portraiturewith the greatest intensity yet produced, by procuringthe coincidence of the chemical actinic and visual foci.The spherical aberration is also corrected very carefully,both in the central and oblique pencils.
One of the exhibitors of photographs, JI. EverabdBi.anquart, proposed the use of a white chamber, foraccelerating the process; but there are serious objectionsto its adoption, and it therefore is not used.
The object-glasses exhibited are, for the most part,achromatic and double, and consist of two lenses placedat a distance from each other. A photographic object-glass without defect is yet a desideratum.
Ross (No. 254, pp. 435, 436) has exhibited the bestcamera in the Exhibition. It is furnished with a doubleachromatic object-lens, about 3 inches aperture ; there isno stop, and no part of the field employed which does notreceive plenty of light; so that the corners as well as themiddle of the picture are well illuminated. The field isflat, and the image is very perfect up to the edge. It has arevolving and adjusting back-board for the reception oftwo plates. The same exhibitor has a second camera,furnished with a single achromatic lens of small aperture.The glass of this instrument having been removed, theimage could not be examined.
Henneman and Maloxe(No. 297, pp. 441, 442) exhibita camera by Ross. It is furnished with a single object-glass, aperture 4) inches, the light is admitted throughapertures 0'2 inch, 0'4 inch, 0'8 inch diameter, at about4 j inches, or at about one diameter of the lens from itssurface, the combination being mounted on a brass coneattached to a mahogany plate, which slides and revolveson the front of the box, to allow any given point of thepicture-plate to become the centre of the field. The
picture-board is 84 by 10 inches; the focus varies from10 inches to 17 inches according to the distance.
Knight and Sons (No. 453, pp. 462, 463) exhibit acamera, the oak stand of which is solidly constructed andpretty firm. It has adjustments for height and azimuth,but not for angular altitude, and has no level. It isfurnished with a double picture-plate. The box expandsfrom 9.j to 14 inches. There is no lens, and consequentlythe image could not be examined. The same exhibitorhas a second camera, in a neat, flat, folding mahoganybox, with hinges, which closes up lengthways. It ison a slight, unstable tripod stand, made by cross bracings.The aperture of the object-glass (a single achromatic forlandscapes) is about 2j inches; the aperture in front ofthe glass is O'O inches, placed at 3J inches in front of thelens. A projection placed in front of the aperture keepsoff stray light. The lens is mounted on a slide to adjustto focus, and its focal length is about 12 inches. No raycan reach the corners of the picture when the lens isbrought home, and only very little light when out as faras it will go.
Horne, Thornthwaite, and Wood (No. 220, pp. 434,435) exhibit a camera with a double achromatic object-glass, whose aperture is about 2$ inches. The size ofthe picture is 8 by 7 inches. The frame allows of twopapers being placed in at one time. The box is madeto fold together, and is a fine specimen of beautiful, neat,mahogany work, with many good contrivances to keepout light. There is no speciality in the construction ofthe daguerreotype and ealotype apparatus of these exhi-bitors, excepting a mode of iodizing and bromizing theplates, by sliders of great neatness; the exquisite work-manship of their several articles; and the general arrange-ments for their use in daylight. Some very fine specimensof chemicals used in the process of photography are alsoexhibited. A Prize Medal was awarded to Messrs. Horneand Co.
Claudet (No. 296, pp. 440, 441) has exhibited cameras;the largest has an aperture of 3 inches in diameter,double achromatic object-glass; when the whole apertureis open, about one-third of the breadth of the lens is cutoff on either side, so that only about one-third of thebreadth of the picture receives full light from the lens,and the illumination is in consequence very unequal.The image is good and the field is flat.
In Claudet’s multiplying camera, the multiplying isperformed by cross-sliding motions of the picture-plate,performed by two racks, working at right angles to eachother, so as to present different parts of the picture-platesuccessively to the axis of the lens, exactness beingsecured by the division of the racks into inches and tenthsof inches. The camera is short focussed, to give smallminiature portraits, either presenting the same individualin different aspects, or several grouped together. Theobject-glass is double achromatic: its aperture is 3 inches,separated by 6 inches on a slide-rack to work in andout of the box ; there are no diaphragms interposed.'Pile front of the box carrying the object-glasses openswith a hinge. The tube projects one-eighth of an inchin front, outside of the object-glass, to cut off stray light.The focus is very short, having about 5 inches, extensibleto about 8 inches by approach, within limits of motion.By focus is meant the distance of the picture-frame fromthe hinder surface of the hinder lens.
Willatts (No. 265, p. 437) exhibits a portable photo-graphic camera with a flexible cloth body instead of awooden one; it is furnished with horizontal movement,and is adjustable to lenses of various focal lengths; ithas, also, an angular adjustment of the frame of thelenses, the latter for the purpose of keeping the image inthe centre of the frame without altering the position ofthe camera. The size of the photographs is 1U4 hv84 inches. The cloth body of the instrument is mountedby flexible vulcanized caoutchouc bands at each extremity,and is thus firmly attached to the ends of the camera.The whole instrument is easily taken to pieces and puttogether, and occupies but a small space. The imagewas not examined.
Vari.ey and Son (No. 257, p. 436) exhibit a singlereflecting camera. This is a plain speculum with thin