Saturday, 21 April 2012

Scene dynamic range

When referring to dynamic range in a picture we are talking about the number of F stops between the darkest area and brightest highlight. If a scene we wish to capture exceeds the dynamic range of our camera we have to make a decision. Do we lose detail in the shadows or the highlights?

I have captured five scenes, each with different lighting and measured the brightest and darkest areas. These are shown on the sketch that accompanies each image.

Image 1. The park. F8 @ 1/80, 100 ISO, 50mm.
My notebook with the darkest and lightest metered values shown.
Image 1 (above).
The lighting for this shot was a clear bright day late afternoon about 4 o'clock. The shot was taken in the open although there are shadows from surrounding trees across the path.  The darkest area is the patch roughly in the centre of the picture. This metered at 1/15 @ F8. The lightest part is the sky in the top left. This metered at 1/800 @ F8. This is a 5 and 2/3's stop range. I have my camera set at 1/3 stop intervals. I would rate this as a fairly average dynamic range.

Image 2.
For this image I wanted to work with low contrasts. I set up a still life consisting of some glass vases which were placed on a piece of silver coloured card. I set this up in my conservatory which has a plastic roof and provides a very diffused lighting. The set-up was shot on a sunny day around mid day. The camera was tripod mounted.

Image 2, Glass. F11 @ 1/60, 100 ISO. 105mm.
The darkest and lightest areas.
I metered using the camera meter set to evaluative metering for the shot and changed to spot metering to measure the bright and dark areas. In this image there are not really any clearly defined highlights or dark areas. After metering several darker patches, I ended up using a reading from the middle of the frame for a highlight and from the dark edge of the right hand vase for the darkest area. The measurements were 1/80 @ F11 for the brightest part and 1/50 @ F11 for the darkest. The exposure range for this set-up is a mere 2/3 of a stop.