Friday, 6 April 2012

My camera's dynamic range

In this scene I have set up a shot where the camera is just short of highlight clipping on the white card. I have used evaluative metering to measure the whole scene. This has resulted in a somewhat darker scene than I would normally shoot.

Scene as shot. F22 1/125 Evaluative metering.

After taking the picture I measured exposure at various points. When using spot metering the card came in at 1/100 @ F22. The small difference could be the brightness of the sun changing between shooting the scene and measuring or due to the change in metering systems.

I picked several different points on the car based on how bright they appeared to the eye. The darkest area was the gap between the tyre and the wheel arch which measured 4 seconds at F22. The brightest part (after the card) was a patch of light on the reflective hub cap.

Exposure measurements taken at various points.
The total range from darkest to lightest runs from 4 seconds at F22 to 1/100 of a second at F22 - a range of 8 2/3 stops.

Below we can see what the darkest area of the image looks like if we ramp up the exposure. Digital noise is making it difficult to see the detail in the darkest area of the wheel arch (below).

Exposure ramped up to show digital noise competing with detail.
This exercise would suggest that my camera has a range of approximately 8 2/3 stops, although you could argue that it is slightly less as the darkest point is very noisy.