Wednesday, 26 June 2013

Exercise: Contrast and shadow fill

In this exercise we are looking at ways of controlling contrast and filling shadow by means of reflective surfaces.  This is an effective alternative to using additional lights in order to achieve the same effect, particularly when working with natural light.  Here, however, I am using artificial lights throughout in order to demonstrate the different effects.

Once again, my patient mannequin is roped in to assist.  The lighting set up is simple as shown in the diagram below.  This diagram shows multiple reflectors, as they were used in different stages, as well as the two lighting sources, a bare flash (Speedlite) and a softbox.
The exercise is in several parts, with, first of all a reference shot using flash without modifier and no reflector and then a second shot using a diffuser (softbox).  During this exercise, the Speedlite was used at half power and the camera settings were:

  • bare flash - ISO 100, f/22, 1/125 sec; and 
  • softbox - ISO 100, f16, 1/125 sec

Bare flash                                               Softbox
These two reference shots clearly demonstrate the difference in contrast between them.  The light from the softbox is a much softer light and provides a smoother transition from light to shadow as well as achieving a more even tone.

The following sequence demonstrating shadow fill, making use of reflectors all use the softbox as the light source.  Apart from the silver foil sequence, I used a commercial, generic, 5-in-1 reflector obtained from Warehouse Express (wex) at a photo show.  As the silver foil behaves differently to the material, I used that in preference.
White 1 m                                              White 1/2 m
This first pair of the sequence also illustrates the effect of the inverse square law.  When the distance doubles,  the intensity of the light falling on the subject decreases by a factor of four.  A white reflector creates a soft light and this can be seen here.  Reducing the distance from the initial 1 metre to 1/2 metre increased visibly (4 times) the amount of light falling on the head, filling in the shadow very well.  The closer the light source is, the larger it becomes in relation to the subject and the softer that light becomes.  This can be seen here with the soft fill from the reflector.
Matt                                                                Shiny                                                         Crumpled
The results of using silver foil with the matt and shiny sides and then the crumpled shiny side did not entirely happen as I had expected.  I expected that with the crumpled shiny side there would be light loss due to being scattered, but this also would create a softer light compared to that hitting the foil in the first place.  This soft light, reducing contrast can be seen here.  It is the difference between the matt and shiny surfaces which I found interesting.  I expected the matt surface to produce a softer fill, but seemingly, it has also provided a higher intensity of fill compared to the shiny surface of the foil.  Expectedly, the shiny surface has a higher contrast when compared to matt, but in theory it should have the same quality as the original source. By that I mean, if a hard light strikes a smooth, mirror-like surface, then hard light would be reflected, whereas a light from a soft or diffused source would reflect soft light.  There is one further variable to be considered here.  As the light has travelled further from the diffused source than that which falls on the subject nearest the source, then the light will have decreased in intensity and will be less soft as the light source is further away.
Gold                                                     Black
I wanted also to show the effect of gold and back surfaces.  The warm light can be clearly seen creating a warmer fill in the shadow area.  The effect of the black surface, which is subtractive, increases contrast and adds depth to the shadows.

Arranging the shots in order of greatest shadow / contrast to least, I have created the above, with greatest top left, running along top row to bottom row least as bottom right.

The results are:

  • black;
  • white at 1 metre;
  • crumpled shiny foil;
  • shiny foil;
  • matt foil;
  • white at 1/2 metre.

Out of interest, I repeated the exercise using the bare flash.  The net effect is much the same, taking into account the harsher light and therefore higher contrast, particularly evident in the main sharply defined shadow line running across the head.


How to control & use photographic lighting - David Brooks

Portrait Photography, Secrets of Posing & Lighting - Mark Cleghorn

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