From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Instruction manual for the SEI Exposure Photometer.
| Identifier | ExFiles\Box 168a\3\ img511 | |
| Date | 24th September 1940 guessed | |
| ILFORD presents the SEI Exposure Photometer USES A.{Mr Adams} Determination of camera exposures for making negatives in general photography. B. Determination of exposures in reversal processes. C. Determination of exposures in copying. D.{John DeLooze - Company Secretary} Determination of exposures in enlarging. E.{Mr Elliott - Chief Engineer} Measurement of transmission and reflection densities. F.{Mr Friese} Measurement of brightness and illumination levels. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} Determination of other data of interest to photographers and illuminating engineers. GENERAL DESCRIPTION AND PRINCIPLE OF OPERATION This is a light-measuring instrument containing its own comparison lamp which is set by the user to give standard output. The photoelectric cell and microammeter necessary for standardising the lamp are contained within the body of the instrument. The scene to be studied is viewed through the telescope of the instrument and a small spot in the middle of the field of view is made to coincide with that part of the scene, the brightness of which is required to be known. The photometric setting is then made by causing the brightness of the spot to match that of the scene. The instrument possesses two outstanding advantages over most photographic exposure meters: it can be used to measure the brightness of very small areas in the scene—spot in the field of view subtending an angle of only ½°, and the range of brightness which may be measured is a million to one, accommodating dark surfaces in interiors and brilliantly lighted skies. Instructions are given here for finding camera exposures: A, in making negatives for which the deepest shadow to be recorded is taken as the critical factor; and B, in making positives by the reversal method for which the brightest highlight is used. The other applications listed opposite are described in the booklet sent out with the instrument. Note: The instrument is supplied without a battery. Instructions for making the instrument ready for use are given in paragraph 14 under 'Maintenance Instructions.' A.{Mr Adams}—CAMERA EXPOSURES FOR MAKING NEGATIVES IN GENERAL PHOTOGRAPHY 1 Set the film scale. For ordinary black and white negative making set the black index on the narrow knurled ring (2) opposite the appropriate speed number on the Film Speed Number Scale (10). The meter is graduated in British Standard Exposure Indices. The following conversion table will enable the appropriate exposure index to be derived from other speed indices:— Speed Conversion Table. The values given are for daylight use and allowance for other light sources must be made in accordance with the film or plate manufacturers' instructions. S.E.I. Exposure Photometer (British Standard Logarithmic Exposure Index): 16, 19, 22, 25, 28, 31, 34 Scheiner Degrees (British and Continental): 17, 20, 23, 26, 29, 32, 35 D.I.N./10°: 7, 10, 13, 16, 19, 22, 25 Approx. H.{Arthur M. Hanbury - Head Complaints} & D.{John DeLooze - Company Secretary} (British): 100, 200, 400, 800, 1600, 3200, 6400 Weston (Daylight): 2.5, 5, 10, 20, 40, 80, 160 Burroughs Wellcome (Column I) Ilford Group: I A, A B, B C, C D, D E, E F, F G A.S.A. Speed Number (American Standards Assoc.): 3, 6, 12, 25, 50, 100, 200 American Scheiner Degrees: 12, 15, 18, 21, 24, 27, 30 2 Standardise the lamp. Press the black switch button (11) in the broad knurled ring (1) at the bottom of the instrument. Note the position taken by the pointer of the microammeter (5) at the top. Make the pointer coincide with the standard mark by turning the recessed rheostat control (12), which will be found at the lower end of the barrel of the instrument. Release the switch button after standardising. 3 Set the colour-of-the-light corrector. If working by daylight set the knurled disc (3) which is found under the eyepiece (4) of the telescope so that the white spot index is immediately under the telescope. If working in ordinary artificial light set this disc so that the yellow spot index is under the telescope. 4 From the camera position look through the telescope (4 and 6) at the scene to be photographed. 5 Focus the eyepiece to your individual eyesight by sliding it along the barrel of the telescope. The object lens (6) also may be moved outwards if necessary for close work, but for ordinary use it should not be withdrawn. 6 Bring the black photometric spot in the middle of the view to coincide with the image of the darkest part of the scene. | ||