Sunday, 17 February 2013

Exercise: Control the strength of colour

Objective:  to demonstrate how colour changes with exposure.

In this set of images, it is brightness which is being considered.

Brightness is the relative lightness or darkness of a particular color, from black (no brightness) to white (full brightness).  If the sequence of images were therefore to be extended in both direction, from over-exposure to under-exposure, then as expected, they would go from white through to black.

This is achieved by controlling the exposure at the time of shooting.  In the sequence below, the exposure was varied by half a stop.  The first exposure in the sequence being the setting given by the camera's lightmeter and the second receiving half a stop additional exposure; all the remaining exposures being progressively half a stop under exposed from the "norm".

1/125 sec at f/11
R80 G0 B14.1

Looking at the sequence the one thing which becomes apparent is that the quality of the colour changes.  In this case, red goes to pink when it is lighter so no longer is this the true colour. Using the percentage RGB shown in Lightroom, this can be seen as the values change significantly as the exposure varies.  These values are shown in each caption.  As exposure decreases  the Red value decreases significantly, so the Blue component becomes more significant.  Given time I will look at other colours in the same way to see how these colour shifts affect those colours with changes in exposure.  Reading the various reference texts, I have noted that yellow only varies between a medium and very light.  

1/125 sec at f/9.5
R89 G14.6 B19.5

1/125 sec at f/13
R70 G0 B9.1

1/125 sec at f/16
R57 G0 B9.9
1/125 sec at f/19
R44 G0 B10.9