DTP SIG Mug Shots
Meeting October 11, 2001
When I suggested we try to improve the mug-shots we take of our members, once again I was reminded of the diverse technical knowledge of our members. Both Stacey Falconer and Grant Fuller who our members know from their contributions of newsletter covers and their instruction of our Illustrator and Photoshop courses commented.
Here is what I asked them: "I'd like to improve the quality of our mug shots of members. Could one or both of you give us some advice at the DTP SIG on Thursday? I'd like to buy one or two spot lights (pointed at the ceiling for diffused light?) and set up a suitable background in the coffee room where we could pose our subjects. Nothing fancy, but something better than we have now." Their responses follow (slightly edited for this page).
Grant Fuller: Basic Setup
I've had reasonable success with one key light, one reflector (piece of white card, 18 x 24" app.), a tripod for the camera and a dark background cloth. The lamp I use is a quartz halogen shop lamp that can cook a cheeseburger from two blocks away and not suitable for human heads. Bouncing light is tricky because it wants to flatten like the TV newsroom lighting and when printed in B&W it loses even more shape. If we have one patient model while creating the set up, the others can be done quickly.
A simpler approach would be a clip-on lamp with a regular 100w bulb and use the wall or card as a reflector. A dark background could be rigged, it only needs to be about 3 ft square.This at least would eliminate the flash.
Stacey Falconer: Lighting
There are several factors to consider in lighting for even mug shots: light intensity- Most people don't realize that the light drop-off of hot lights or flash are 1/4 for every 1/2 the distance that the flash is from the reflective surface. One of the best rules is to use the same distance scale as the f-stop on a camera. 8 feet compared to 5.6 feet requires twice the amount of light. The same is the same for the rest of the series, if thought of in terms of distance: 2 feet, 2.8 feet, 4, 5.6, 8, 11, 16, 22, 32, 44, etc. Most simple camera mounted flashes can not reach more than 8 - 16 feet and still have enough light.
An extrapolation of this is to have a flash 5.6 feet in front of the subject, and have the background roughly three and a half feet (eight feet) from the flash means that the background is under exposed by one f-stop, or half the amount of light. The camera distance has no relationship to the light intensity, except if the camera is mounted on the camera.
This sort of says, that "keep the background a lot closer than the light".
Flash shadow: a bit of side lighting always helps, but not at the cost of a heavy flash shadow. The best solution is to light the background separate from the subject. This is not always practical, but a key light and a fill light are better than nothing.
Lighting ratios: unless you are a fan of "film noir" keep the key and fill light to 3:1. The formula is very simple- (key+fill)/fill. So if the key light is considered as "prime" lighting, and the fill is 1/2 the key, then the formula dictates that (2+1)/1 = 3/1, or (1+.5)/.5 is still 3/1, or 3:1. The easiest way to get this ratio is to again use the above equation: if the main light is say eight feet away, then the key light is 11 feet away. The same goes with the main light being 4 feet away and the fill being 5.6 feet away.
Lighting types: There are a few general lighting types to consider. Let us say you don't want the person head on, but slightly directed to one side or the other. Left or right doesn't matter, except where the key and fill light come from. If the key is on the far side of the face, and most of the exposed face is darker, then it is called "short lighting". When the broad side of the face receives the key light, and the far side of the face receives the fill, then it is called broad lighting. There is a couple of variations, the most important being "Rembrandt lighting", where the key light is high and to one side, to create a triangular shadow on the cheekbone. This is also called trap-door lighting after the painter, who would open a trap door on the roof to let in the key light.
Colour temperature: If a flash is not used, then all the lights should be of the same colour temperature. For film this more or less means using a flash or flashes. For a digital camera, this means using the same colour of lighting. The colour temperature of a standard light bulb is 2800 k, or very red. Halogen work lights are about 3200 k. Real movie set lights are about 3400 K. Pushed tungsten lights that they used in the 60's for indoor movie film where about 3800 K. Flashes are 5000 to 5500 K. Cool white fluorescent lights are daylight with about 30 CC (a standard in colour correction filters) too much green. Therefore, keep the colour temperature as consistent as possible, or reduce the ambient light by overpowering the existing light by at least two f-stops or more.
One of the more easy solutions is to shoot a subject in sunlight and use a bit of fill. Obviously this isn't that easy in Victoria, and especially at night. Sometimes the use of a reflector is the easiest solution, such as a white piece of foam-core board, or even a black reflector cloth or board on the fill side.
The last point is the size of the light source. The larger the light source, such as through a diffuser or matte cloth of some kind (the photographers' soft box), the better the gradation between light and shadow or key and fill lights.
So, in conclusion if a simple key and fill lighting set up is to be used, it can be relatively inexpensive (a couple of halogen reflector work lights) with a diffuser panel in front of each, and a one f-stop distance closer from the subject than the other, with the background as close as possible to the subject unless distinct shadows are visible.
Forget the "bounce off the ceiling" stuff, it's hard to control. I've had to fix far too many wedding photos where the photographer didn't understand light, and that was even before Photoshop, though at least with digital cameras you can see the results faster than Polaroid film, which is probably why their stock is taking a nose dive.
