Canpic78 wrote:
Glitzy & patterned surfaces will reflect light in many different ways such as Christmas wrapping paper. Flash doesn't work out well, as it creates too much light in one spot, so I put the object in the shade. A bright gold color turned out green in some places. What is the best light for these types of photos?
Short answer: locate the light outside the "family of angles" that will reflect into your camera lens,
or use diffuse light.
The problem is "specular reflection": light from a point source striking a surface that is smooth
and shiney, causing a beam of light to be reflected into the camera. A surface that diffuses light creates
only a diffuse reflection which is less concentrated and so does not cause a probem. A piece of white
paper creates a diffuse reflection; a mirror creates a specular reflection.
If it were one tiny mirror, the chances of it reflecting your flash into your camera lens would be small.
But if the surface is large and covered in tiny mirrors, there is very good chance it will hit your lens.
Not to worry: you can still dodge the bullets, but you have to know which spots are safe.
Light reflect soff a perfectly flat surface so that the angle at which it leaves the surface is the same
as the angle at which it hit the surface, and it will stay in the same plane (Law of Reflection).
Remember that a light that is far away (such as the sun or a distant flash) strikes all parts of a surface
at close the the same angle. So no matter where you stand on the opposites side of a pond from the
sun, if you point the camera at the pond some part of the pond will reflect it back into the lens.
When the light is closer and the surface is smaller, then there is only a small "family of angles" that
will catch a reflection from a stationary light.
One way to see this simple specular reflection from a flat object is to set a mirror the size of the object
on top of the object. Then you can see quite easily where the light goes.
When the shiney surface has texture, this family of angles may get quite large. You may need to experiment
to find the best placement. You can move either the camera or the light--whichever is more convenient.
When the subject consists (as most do) of several planes, then you avoid reflections from each plane.
The subject of reflections is thoroughly explained with many examples in
Light: Science and Magic,
5th Edition, by Fil Hunter, Steven Biver, and Paul Fuqua (New York and London: Focal Press, 2015.
ISBN 978-0-415-71940-7, paperback).
Alternatively, try a very difuse light source. You could try bouncing flash off the ceiling, and if that doesn't
work, off a wall. Makes sure no direct flash falls on the subject. (Soft boxes and small umbrellas are not
diffuse enough to eliminated specular reflections.)
If the surface causing the refllections doesn't conduct electricity, then a polarizer filter might help.
But metal surfaces (e.g., aluminum foil) do not polarize light, so if it's tinsel causing the reflections,
a CPL won't help.