mardi 1 février 2005

Multiple Images... Photography by Numbers Sometimes there are photo techniques in the back of your mind that you have never used... you know how they are applied but don't know if they will ever be applicable to your kind of photography. There are several such techniques in my head... but luckily the trends which come and go in the arts, and photography is an art, have moved on to save me the visual embarrassment of exposing myself to the ridicule of those both above and below me in the pecking order of credibility in print. As a freelance photographer there was one phrase which always haunted me and sometimes taunted me... "You're only as good as the last job you do." What it meant was that if I goofed with my last set of shots for a client... then that was possibly, or more like probably, the last time their voice would be at the end of the phone with an offer of more work. That's why as a freelancer it was wiser to have as many varied outlets for your services as possible and not have all your eggs in the same basket. So by playing the numbers game I frequently used a photo technique which was simple to do but difficult to keep simple... that of using multiple-exposures... but with a twist! Multiple-images are what they say... more than one image recorded on (usually) the same frame of film. I can't think, off hand, of any cameras which can't be used for this technique... and I have to admit that with modern auto-everything cameras it's far easier to do successfully than with the older metal, mechanical, meterless cameras I tend to use. What you do is first decide on the number of exposures which would make an interesting final image... then calculate the exposure required for each individual image which becomes the same exposure you would have used with a single shot... make the adjustments... then fire away. With my mechanical cameras I have to press the shutter once... press the camera rewind button in to release the wind-on clutch... cap the lens and wind-on... uncap the lens and take the second shot... and so on maybe nine, sixteen, twenty-five times! However, when I'm serious about multiple-exposures I use a motor-driven camera keeping my finger or thumb on the rewind button/switch whilst firing away on the motor-drive. On the most modern camera I ever used, a Nikon F4 about 10 years ago, there was an automatic feature to program the number of shots required and the camera did the rest. I also had an MF-23 Multi Function Back for the Nikon F4 which once programmed would do many things at intervals, including bracketing multi-exposures at different times of the day... but that's not photography to my mind. No doubt some of today's cameras pause if a cloud obscures the sun so as not to ruin a "perfect" shot. The exposure compensation required for multiple-exposures is easy to calculate in your head... if you're reasonably good at numbers. Think of a normal exposure, say, 1/125 sec at f/8 as being the fixed number. If you take two exposures on the same frame of film then the exposure is halved for each shot making two exposures of 1/250 sec at f/8... or two exposures of 1/125 sec at f/11. Likewise for four exposures on one frame of film you take four of 1/500 sec at f/8 or four of 1/125 sec at f/16. Alternatively you can change the film's ISO setting on your camera or meter... by doubling the number of shots you double the film speed... from, say, ISO 50 to 100, or from ISO 100 to 200. If you make four shots on a single frame change the film speed by two stops from, say, ISO 50 to 200. If you make nine shots on a single frame, which I do mostly as it appears to be a good balance between "impressionism" and "abstraction" with some "recognition" retained, then change the film's ISO rating by three steps... from ISO 50 to 400. Twenty-five shots would need the equivalent of five stops change... from ISO 50 to 800... but with this number things can go awry because of the build-up, or lack of overlapping density on the film. You have to experiment to get the best from the technique... and if I'm in the multi-exposure mood then half a film or more is exposed on the same, or similar subjects. Of the two subjects here the modern office block in central London consumed two films at one sitting... or 72 frames... or perhaps 500 to 600 exposures... from which I know I have half a dozen shots worth reproducing in print or on screen... the rest were consigned to the round filing cabinet under the desk. Similarly with the multi-exposures of Autumn foliage at Westonbirt Aboretum, in Gloucestershire, out of half a dozen films exposed on a Hasselblad 500C I got maybe half a dozen good shots and a worn out wrist from cranking the rewind handle so many times! 9:51:46 PM    comment []