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 page for a photometer or exposure meter, detailing camera exposures and maintenance.
| Identifier | ExFiles\Box 168a\3\ img512 | |
| Date | 24th September 1940 guessed | |
| 7 Press the switch button again and try to make the spot match the part of the scene selected as in the previous paragraph by turning the broad knurled ring (1). If the spot is always too dark or too light the image of the object must be darkened or brightened by turning the knurled disc (7) so that the photometric spot can be matched. This knurled disc will be found to carry three spot indices. One of these is to be set immediately under the middle of the telescope objective as follows:- for bright scenes use the blue spot index for normal scenes use the white spot index for dark scenes use the red spot index 8 Read the time of exposure on the appropriate scale (8) in relation to the f/number scale (9) taking care to select the exposure time scale of the same colour as the index spot used for the operation described in the previous paragraph. B.-CAMERA EXPOSURES FOR REVERSAL WORK (COLOUR OR BLACK AND WHITE) 9 Set the film scale by bringing the white index on the knurled ring (2) opposite the appropriate number on the Film Speed Number Scale (10). (See paragraph 1 for table of equivalent speed numbers.) 10 Make the adjustments described in paragraphs 2 (to standardise the lamp), 3 (to set the colour-of-the-light corrector), and 5 (to focus the telescope). 11 Select for measurement the most brightly lit white object in the scene. If no such object exists an artificial highlight should be made by holding a piece of matt white paper or card so that it is illuminated in the same manner as the subject. The card should be held at right angles to the direction of light from the main source in order to give the maximum brightness. 12 Make the photometric measurement of the highlight in the same way as described for the shadow in paragraphs 6 and 7. 13 Read the exposure as described in paragraph 8. For 16 frames cine work read off the stop on scale 9 against the cine index @ on the appropriate scale 8. MAINTENANCE INSTRUCTIONS 14 Battery. The battery to be used is a cylindrical one, size U.2. To ensure good contact choose a make without a pip on the centre brass terminal (e.g. G.E.C.). To prepare the battery for use, strip from it the insulating paper sleeve, clean both end contacting surfaces with emery cloth and smear lightly with Vaseline. Open the base of the photometer by holding fast the Speed and Lens Aperture scales and unscrewing the bottom of the instrument by turning the broad knurled ring (1). Insert the battery, base first, into the cavity. Replace the base of the instrument. WARNING: The battery should be inspected occasionally to see that no corrosive chemicals are exuding from it. If the instrument is to be stored or left disused, the battery should be removed. 15 Lamp Bulb. To replace the lamp bulb unscrew the base and remove the battery. Withdraw the tube lining the cavity in which the battery was situated. The bulb is mounted at the end of this tube lining. Slacken the bulb clamping screw, withdraw the locking plate and take out the bulb. Replace this by the spare special bulb supplied with the instrument. PRICE £36 . 0 . 0 (Free of Purchase Tax) Leather Carrying Case £1 . 10 . 0 (Plus Purchase Tax) Distributors ILFORD LIMITED, ILFORD, LONDON Printed in England | ||