People talk about soft and hard light but really it is just a gradation between them. How does one measure the hardness of light falling on the subject as opposed to the hardness of the source?
Clearly hardness of the source would be measured by calculating the angle between the distance of the source and the size of the source.
So the sun would be the Tan-1(Sun Height / Sun Distance) = 0.53 degrees i.e. extremely sharp.
A blonde with reflectors 0.1m diameter positioned about 5 meters away from subject would be Tan^-1 (0.1/5) = 1.14 degrees i.e very sharp.
A softbox 2m high and 2m from subject would be Tan^-1 (2/2) = 45 degrees i.e. soft
However when there are obstacles or diffussion in the way the actual hardness of light falling on the subject is different - so how does one measure this?
In some instances the diffuser or diffusion becomes the new source - e.g. a tweenie bounced off a muslin - the muslin is now the source if the muslin is 2 meters away from the subject and 2m high the light falling on the subject now has a hardness of 45 degrees (i.e. soft).
But when the sun becomes diffused by haze, mist, fog, cloud covering, etc. the effective sharpness of the shadows surely changes - until it is overcast and then the angle of hardness is 180 degrees - totally diffused and no shadows.
I was walking in the countryside on Sunday and the lighting was beautiful. Something I would like to replicate.
It was overcast, not heavy overcast and a low sun was diffused through some more whispy clouds.
So I took out my Lee swatchbook and observed the colours that surrounded me. I measured the angle at 10 degress, and the shadows to be about 4-5 shows darker than the highlights.
But I had no idea how to measure the hardness of the shadows. The clouds were diffusing the sunlight and a rough guess would be 80% if 100% is a perfect sharp line. I presuming the sharpness of the sun is less in winter than in July due to travelling at a lower angle, and hence more diffusion through the atmosphere. Is there a tool for such a thing? Is there a known chart for the hardness of sunlight under various conditions - i.e. December vs July. Does the sharpness actually change between winter and summer due to a lower trajectory and more atmosphere to travel through or only intensities?