What is Coverage, Edge transfer, Shadow definition, Shadow contrast, Highlights?

What is Coverage, Edge transfer, Shadow definition, Shadow contrast, Highlights?

© Bron Elektronik AG - by Urs Recher

With the “Famous Five”, we have a complete tool to analyse light. When you see a photograph or when you have a certain light mood in mind, you can easily figure out which light shaper you should use to get the desired effect.


1. Coverage:
The coverage of a lightshaper tells us how the light is distributed.

It can be:
- Even (e.g. big softbox behind camera, open reflectors defocussed, Para FB defocussed, optical snoots)
- Center weighted (e.g. open reflector focussed, Para FB focussed, Reflector Par, some fresnell spots, any lightshaper with honeycomb grids)
- Linear graduated: (e.g. long and narrow softboxes at short distance, striplites and lightbars as sidelights)

The coverage of a Par reflector (here I used three of them) is clearly centerweighted.




2. Edgetransfer:
The edgetransfer gives us an idea, how abrupt the light ends, once we reach the end of the lightangle.

It can be:
- Very sharp (e.g. optical snoots and attachments)
- Quite sharp (fresnell spots, Satelite evolution, Minisatelite and honeycomb grids)
- Soft (e.g. Softboxes, acrylic arealights such as Hazylight-Soft and boxlite, open reflectors)
- Non-existent (bare bulp, balloon, litestick and lightbar)

As we can see in the reflection in the eyes, the light is coming from the right. Nevertheless we notice a light fall off on both sides of the face. On the left it is a”normal” shadow, on the right it is the edge transfer of a Pulsoflex C.




3. Shadow definition:
Shadows of hard lights are highly defined while soft lights have a low shadow definition. Diffused lights have no shadows at all. (Also read Eye school part one: hard, soft and diffused light)

The shadow of the no-parking sign is already less sharp than the shadow of the model because he is further away from the relatively hard light (a standard reflector P70).




4. Shadow contrast:
Working in a black or very large studio we can expect black shadows wherever we do not intentionally illuminate our object.

In smaller or brighter painted environments however light can be bounced back from the walls and fill in the shadows. In this situation the shadow contrast depends directly on the lightangle of our source: Directed spots or normal reflectors with honeycomb grids do not hit the walls very much resulting in black shadows. Working with the broncolor balloon we have a lightangle of 360°. All the studiowalls get a lot of light and the shadows are very bright.

When we are working with such a “wide-angle-light”, the inverse square law (see 1.3) still gives us a possibility to control our shadows: The closer we get (to the object or model) the faster the light falls off after hitting it. This makes the walls (and the floors and ceilings) darker and the shadow contrast is increasing.

In this shot we can see clearly defined shadows (hard light) but the contrast of these hard shadows is very low.




5. Highlights:
In general we can say that the highlights of hard lights are very small and completely burnt. Those of soft lights show clearly the form of the lightshaper (rectangular or round) and might still be burnt a little. Diffuse lights finally should not show any dominant highlight anymore, but they can reduce the colors dramatically ( e.g. the color of eyes in a diffuse portrait).

The brightnes of the highlights give you additional information about the distance from the light to the object or model. The thumb rule is: When the light shaper is further away, the highlight is brighter. This fact is precisely explaint in the Urs Recher book “Light Architecture”.

Shooting cutlery (or any shiny, polished object) is nothing else than shooting the reflections of the light source. Here, this is an acrylic diffuser with a standard reflector P70 with honeycomb grids behind it. The narrow white reflection is made with a Striplite 60.


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