Thursday, October 20, 2011
Nelson's column as seen from the National Gallery at Trafalgar Square in London.
In this photo, relying on the camera's exposure system can be a problem. What I don't want is a wash out sky and I don't care about the shadow detail on the National Gallery column. There is plenty of time for manual exposure - Admiral Nelson is not going to walk away! I use spot meter to read off the blue sky and add 1 stop. Then I read off the white cloud to make sure that it is not more than 2 stops over exposed. The exposure was 1/1000 sec, f/8, ISO 200.
That is equivalent to 1/250 sec, f/16, ISO 200 - sunny 16 exposure. What is sunny 16? In those olden days when we use film, the rule of thumb for exposure in bright sunlight is to set aperture at f/16 and shutter speed is the reciprocal of film speed. In this case should be 1/200 sec. The nearest available shutter speed at that time was 1/250 sec. Adjustment for shutter speed was on the top dial and only at 1 stop increment. What worked before still apply today. After all the advanced evaluative/matrix/RGB metering system, I could just set the exposure at sunny 16 and get perfect exposure.
I prefer the size of the Nelson's column to appear slightly bigger relative to the Nationaly Gallery column. To do that I have to walk away further and use longer focal length (go figure!). But my back is already against a wall.