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THE CELLULOID IMAGE
|REVIEW PAGE - from Amateur Cine World July 27, 1961|
THE BOLEX B8SL
(Std 8mm double-run)
|The twin-turret B8SL, with the normal lens
in the taking position below the light meter.
Starting button adjoins the name plate; in the
same side, above, is the knurled wheel for
safety lock, continuous run, etc., and below,
the threaded socket for a cable release.
The scale shows the light meter setttings
corresponding to film speeds of between
10 and 40 ASA.
Test Reports normally deal with newly released equipment. We make an exception in favour of the B8SL in response to an unusually large number of requests.
BOLEX B8SL STD 8MM CINE CAMERA
THE B8SL is the twin-lens turret version of the simplest of the Bolex light-meter cameras for 8mm., the G8SL. It has one running speed (18 f.p.s.), a single-frame release, and a simple optical viewfinder. The turret is designed for the standard "D" mount, so that the user has a wide choice of lenses; those supplied with the camera are a 13mm. f/l.9 fixed-focus and a 36mm. f/2-8 focusing telephoto.
Body - Light alloy die castings, with black grained leatherette side panels, and bright metal beading round the edges. The door, hinged at the back and fastened by a central catch, cannot be closed if the gate has been left open. The door catch can be folded flat upwards or downwards to cover either single or double dots marked on the metal underneath, thus showing at a glance whether the first or second run of film is being exposed - a point easily forgotten if the camera has been put away for some time.
Light trapping is by a 1/8inch deep tongue-and-groove join all round (except where the inner ridge is cut away in two places to clear the spools); for extra light-tightness, the groove is lined most of the way with black cord.
A standard English (1/4inch Whit.) tripod bush is located at the front right-hand corner of the base - not, we felt, the ideal position. Apart from making a tripod slightly unbalanced, the off-centre bush causes uneven pressure, which could prevent the camera from sitting squarely on a pan-and-tilt platform covered with a resilient material; any resulting tilt could easily be allowed for, of course, but spirit levels built into the panning head would no longer be accurate.
Gate - The front plate is relieved so that the emulsion side of the film is not rubbed in the picture area. The pressure plate behind is not relieved, but its flat surface is highly polished and thus unlikely to mark the base side if kept clean. Both parts of the gate are blackened to prevent halation.
For threading, the gate is opened by pulling a small lever; this allows the pressure plate to swing back under spring tension, withdraws the claw from the film path, and re-sets the footage counter to zero. To close the gate, the lever is pushed forward. The pressure plate can be pulled right out of the camera for cleaning; when that is done, the front plate remains fairly inaccessible, but there is just enough room to clean it and the aperture with a piece of chamois leather or soft cloth wrapped around a match or orange stick.
Sideways positioning of the film in the gate is by an unusual arrangement of fixed and sprung guides. Their combined effect is to give the film a slight diagonal bias which, say Bolex, improves steadiness. In our tests, the performance of the B8SL certainly supported the makers' claim.
Intermittent - A fully retracting claw describes a true D-path motion and engages the film through the back, the perforation used for pull-down being the first below the bottom of the gate (+1). The rotating disc shutter has an opening of 150°, giving an exposure of 1/43 second at the 18 frames per second taking speed; the inertia of the mechanism increases the single-frame exposure time to about 1/30 second.
Film Path - Above the gate, a relieved roller on a sprung arm and, below the gate, a rubber covered post are used to isolate the intermittent movement from the spools. The upper spool spindle is plain, and the lower carries a single dog for take-up. The take-up spool supplied with the camera has four slots in each side, which may present difficulties if one wants to transfer a half-exposed reel from the B8SL to a camera with spindles coded for orthodox spools with three slots in one side and four in the other. Although such occasions are rare, it seems a pity to have departed from established international practice in this respect; moreover, coded spindles would prevent incorrect insertion of a film in the BSSL.
Take-up drive is through a slipping clutch which has its tension set to operate only with the assistance of the claw; after the last perforation has cleared the claw, therefore, the end of the film remains trapped in the gate and cannot spring loose on the spool.
Footage Counter - Driven from the mechanism, this gives readings on a dial marked at every foot and numbered at every 2 foot. Travelling past an index mark in a window at the rear of the camera, the dial shows the amount of film exposed and re-sets automatically to the starting position when the camera gate is opened.
The START mark is set at 4 foot from "0" on the counter scale to give the correct length of leader. There is, however, no corresponding mark on the dial for the trailer. Instead, when 25 feet has been exposed, the counter makes a click as a warning that the useful part of the film is at an end. After ten further clicks, the user knows that all the protective trailer has been run off, but the counter reading remains at "25." A slight disadvantage of this method is that, in surroundings too noisy for the first click to be heard, one could not tell from the reading of "25" whether this point had just been reached or whether part of the scene had already been allowed to run on the trailer, which may be lost in processing. It would be better if the dial continued to advance with the clicks, though this might raise constructional difficulties.
Motor - The spring is wound by a fold-over ratchet-action key which can be turned while the mechanism is running. A full wind of 11 turns transports just under 7 feet of film - a maximum run of 32 seconds - before the mechanism automatically cuts out. When the cut-out operates, the camera stops with the shutter open; this is worth remembering, for there is a risk of fogging spreading to the other "run" of the film, and possibly spoiling the middle of a shot, if the shutter is left open for long with the lens uncapped.
Motor speed is controlled by a centrifugal governor. On the model tested, this was very efficient; the average running speed was exactly the nominal 18.0 frames per second during the first 10 seconds of each run, 17.7 f.p.s. during the 10-20 second period and 17.3 f.p.s. between 20 and 30 seconds.
Release - The mechanism is controlled by a small sliding catch on the front right-hand corner of the body. Associated with it is a serrated disc, placed iust above, which is turned to one of the four positions: SECURITY LOCK, SINGLE FRAME (not exposed until the starting catch is released), NORMAL RUN and CONTINUOUS LOCK-ON RUN. Below the release button is a socket for a standard parallel-thread cable release.
Viewfinder - Of the simple optical type, this gives an image of roughly two-thirds life-size. The whole field corresponds to the area included by the standard 13mm. lens, and engraved rectangles show the fields covered by 25mm. and 36mm. lenses. Field adaptors for use with 5.5mm. or 6.5mm. wide-angle lenses are available as extras, as are pairs of parallax-correcting prisms (l foot and 2foot or 25cm. and 50cm.), and special eye-pieces for those with abnormal sight.
The finder axis is 11/16 inch to the right and 1 1/16 inch above the lens axis.
Lenses - The swing turret carries two standard D-mounts spaced 1.25 inch apart. It is firmly indexed by sprung pins and can be rotated in one direction only (clockwise seen from the front).
The Yvar l3mm f/l.9 fixed-focus lens is engraved (in red) with the minimum safe shooting distance for each aperture. The Yvar 36mm. f/2.8 telephoto focuses down to about 1.5 feet; it is fitted with the Kern patent Visifocus depth-of-field indicator in which orange dots, changing with the aperture in use, indicate the limits of sharp focus on the focusing scale. A depth-of-field table is also supplied.
Both lenses are provided with screwed front cap, and for the 36mm. there is a small leather pouch in which it may be stored when another lens (such as a wide-angle) is fitted on the turret.
Exposure Control - The unique feature of the Bolex system is that the photo cell measures the light that will actually fall on the film, so that exposure settings are not influenced by the brightness of objects outside the area included in the picture. Depressing a small lever positions the p.e.c. behind the lens, and in front of the shutter and film, while the measurement is being made. When the release button is operated to start shooting, the cell automatically retracts out of the way.
Exposure is set by matching two needles visible in the viewfinder. One of these, black, is controlled by a galvanometer measuring the light reaching the photo-cell through the taking lens. The other needle, red, is a datum which has to pre-set according to the speed of the film in use.
The first step in using the control is to consult a table on the front of the camera which assigns numbers from 4 to 10 for film sensitivities of 10-40 ASA (11-17° DIN). The red needle is then set in the appropriate position by rotating a knob on the galvanometer housing until the appropriate film sensitivity number is aligned with (normally) a small black arrow. Once made, this adjustment does not have to be altered until a film of different sensitivity is used (or for some special lenses, to be discussed below).
With the red needle correctly set, there is little more to be done. The camera is aimed at the scene, the lever depressed to position the photo electric cell in front of the film, and the iris ring of the taking lens turned until the black needle covers the red. It is a quick and easy routine, and one of its particular merits is that, the setting being based upon the light that will reach the film, allowance is automatically made for the effect of any filters, etc., fitted to the lens (and, indeed, for the lens cap, which, if left on by mistake, will keep the black needle in its bottom position, no matter how much the aperture ring is turned).
The photo electric cell though behind the lens when a reading is made, is closer to the lens than the film. The difference is immaterial with lenses of normal and long focal length, but the marginal rays in the wider cone from a wide-angle lens would result in an incorrect exposure reading. The necessary adjustment is made by shifting the red pointer to a different pre-set position, and this is done by setting the film sensitivity number against a red arrow on the calculator dial, instead of the black arrow used for the normal and tele lens.
Compensation by means of the red arrow is not possible on the BSSL if the film in use is faster than about 20 ASA. For such films, the procedure when using a wide-angle lens is to use the black arrow, align the two needles in the view-finder with the iris control, and then close down the iris by a further stop before shooting the scene. Indeed, even with 10 ASA films, this method may be preferred to repeated re-adjustments of the galvanometer dial when wide-angle and standard lenses are being used in rapid succession.
A similar dodge makes it possible to use the meter for films faster than 40 ASA - the maximum catered for with standard lenses. The film speed is first divided by 2, 4 or 8 (whichever brings it to below 40 ASA), the viewfinder needles are aligned, and the iris then closed down by, respectively, one, two or three stops.
For single-frame exposures, the instruction book recommends setting the index 11/2 units higher than for continuous run; alternatively, the lens can be closed down by half a stop over the normal reading.
To check the zeroing of the galvanometer, two triangular marks on the calculator are matched; the red and black needles in the viewfinder should then be aligned when the camera is held level with the lens capped to prevent light from reaching the photo-cell. The zero can be adjusted by turning a small screw just below the lever positioning the cell, but as the galvanometer is a delicate instrument this is perhaps a job better left to the dealer.
One minor limitation of this excellent exposure system is that a reading cannot be made while actually shooting - to compensate, for example, for a cloud in front of the sun or for a pronounced change in scene brightness during the course of a pan.
Again, like all meters which integrate the light from the whole scene, that in the B8SL can give correct readings only for "average" subjects. With such special cases as a figure standing against a background that is predominantly white or predominantly black - the figure requiring the same exposure in both cases for good rendering of flesh tones - one of the usual remedies must be applied, such as taking the reading from close enough to the subject for the background light to be insignificant. Better still is to take the camera so close that the only light entering the cell is that reflected from the subject's face and then, on returnmg to the shooting position, open the lens by one stop to compensate for the fact that a brighter-than-average scene has been measured. It must be stressed that these departures from normal routine will seldom be required. For the majority of scenes, simple needle matching will give fully acceptable results.
Instruction Booklet - This is comprehensive, well illustrated, and sensibly begins with a brief summary of the instructions for use "If you are impatient to shoot your first film." There are some sound general hints on filming technique. The only fault we could find in an exemplary book was the omission of a depth-of-field scale for various lenses; the loose leaflet included for the telephoto lens could be easily mislaid.
PERFORMANCE - The Bolex B8SL was a pleasant camera to use, both in the hand and on a tripod. A mild complaint must, however, be made of the lens designer for putting the aperture ring at the back of the l3mm. lens and at the front of the telephoto. When groping for it to adjust the meter balance, one too easily handles the wrong ring. With practice, the fingers would no doubt go to the right place every time, but the camera would be still easier to use if the aperture rings of both lenses were at the front.
The exposure meter produced consistently wcll-exposed results, failing to do so only on those exceptional scenes where it was obvious that some correction to the indicated exposure would normally be made.
The picture steadiness, tested by super-imposed shots of a high contrast target, was exceptionally good; in fact, few 8mm. cameras reviewed have scored such high marks here as the B8SL, single-frame exposures were rock-steady, and in continuous-run shots vertical jitter was barely detectable.
The mechanism gets up to speed very quickly - so fast, in fact, that the first frame of each shot is no lighter than its successors. This is not an unmixed blessing, for it makes the start of similar shots harder to find in editing; one obvious remedy is to develop the habit of exposing a single frame with the lens capped between any two shots taken from a single viewpont.
Viewfinder accuracy was fairly good. A moderate error at the top of frame, and part of the error at the bottom, was due to parallax. A very small amount cut off at the sides was a symmetrical error and of no practical importance.
Lenses First Class
Tests of resolving power showed that the 13mm. lens was just a trace soft at full aperture, with definition falling off slightly towards the corners. However, it improved rapidly with only a little stopping down. The 36mm. lens retained good definition and contrast right up to full aperture. With subjects less exacting than our charts, the full-aperture softness of the 13mm. would not be noticeable; on the various pictorial scenes shot during testing, both lenses produced first class results. The focusing scale of the telephoto was correctly calibrated at all distances checked.
The footage counter was found to be accurate and easy to read; its only weakness, as mentioned earlier, is its failure to show how much of the trailer has been run through the gate. The frame line was correctly positioned to bisect the sprocket hole.
The Bolex B8SL measures 2 inches wide by 5 inches high by 5 inches long over the turret and weighs about 21bs. Price (since April, when it was reduced), £59 19s. 9d. cornplete with the two lenses. A black leather wrist-strap is 19s. 2d. extra and an ever-ready case £4 7s. 2d. It is a pleasure to recommend a camera with so many good features as this.
Submitted by Cinex Ltd.
|Light-meter section of the B8SL.
Behind the iris and aligned with
optical axis (arrowed line) is the
circular element of the photo-
electric cell: it moves upwards
automatically, clear of the light
path, when shooting begins.
Current from the cell goes to the
coil (between the horse-shoe
magnet) and deflects the black
needle in the viewfinder.
When the iris is adjusted to
line up this needle with the red
pointer (grey in the diagram),
the correct exposure is set.
First published March 2004 ........ Last updated: 17 August 2009 ........ cel08.htm .......... İMM1X-G.L. Newnham