by Dave Montizambert Published 01/04/2012
I've done much soul searching over these past months of 2012, and I've come to the conclusion that I can't call this column Lighting for Digital X anymore. Digital is trite since almost all photographers are digital now and so digital is taken for granted. So what shall I call it? Lighting For The Hell Of It, or Lighting For Fun And Profit? The first is too "Hell's Angels" and the second only Americans would appreciate. How about my old title "Creating With Light"? Let me know if you hate this or not. Also I've redone my author's image with a snazzy new B&W self portrait, the old one was about 12 years out of date. Anyhow on with the article.My photographic style pushes me to attain maximum theatrical effect with my lighting, which usually entails placing lights to the side or behind my subjects to push shadows across them or towards the camera. To do this kind of lighting effectively one needs to meter and when metering, one needs to be aware of a little incident metering glitch that will invariably befall you.
When a light source is placed beyond 90˚ from the subject camera axis (see Diagram1), the apparent brightness of this backlight (see Image 1 bottom left-hand frame labelled +0), obviously viewed from camera angle, appears brighter than what an incident meter reading of this backlight suggests. Sorry about the uninspired self portrait but it was the help's day off. In fact, the further the source gets from 90˚ towards 180˚, the brighter it appears. For instance, if we repositioned the light to105˚, the effect of this change will appear even brighter than at 90˚, and if then repositioned to 120˚, the effect will appear even brighter than 105˚.
Now conversely, if you take a reflective meter reading from the camera's position with let's say a 1˚ spot meter, the meter will read true. The only problem is, where do you read off the subject, if you read off an area of the flesh that has shine on it caused by the light in question, it will read brighter than if you read off an adjacent non-glare area; if you read off hair or clothing those readings too will read differently. The truth is, to work out lighting ratios and/or exposure with a reflective meter takes more intelligence and time than working with an incident meter. I don't know about you but I try to keep intelligence to a minimum. With an incident meter you simply place it against the subject and point the dome at the light in question, its reading tells you what it wants you to set your camera to, to create what it thinks is a correct exposure for that area - the only problem is, the meter does not consider the camera viewpoint which becomes a problem when your light source sits at an angle greater than 90˚ from the camera.
The solution - schedule in a little time to do a lighting-ratio test using a simple portrait set-up. For my test, I keep it really simple and just set up a main light and a separation light (see Diagram1). The purpose of this test is to show you the correlation between incident meter readings and actual brightness appearance on a subject from a light that is placed beyond 90˚ from your camera axis. Once your set-up is complete, start the test by measuring the strobe placed beyond 90˚ from camera axis with an incident meter. Adjust the light's power output until it reads three stops darker than the camera setting - for instance, if the camera aperture is set to f 8 for a good exposure of the main-light and for depth of field, then the light striking the subject from the light in question should read three stops darker at f 2.8. Even though the backlight reads f 2.8, capture an exposure with your camera still set to f 8. With the first exposure of the test in the bag, turn the light's power up one stop, it should now read f 4. Again capture a frame with the camera still set to f 8.
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