Exercise 8 - dynamic range

More sun, more exercises...

Location: a still cold, but snow free back garden.

ISO (lowest setting) - 200

Noise reduction - off

Highlight - white paper taped to the garden fence

Shadow - the bamboo bed

This seemed like a simple enough exercise, reading it; it also seemed simple when I took my camera into the garden and took a series of photographs. However, once inside doing the write-up I suffered brain freeze. It didn't make sense and I even re-did the exercise twice! I was still struggling but rather than grab the camera again I went for paper and tabulated all three sets of result. Suddenly it was simple again. I have no idea what happened, but it was very strange.



The bamboo bed

Exposure Values

Aperture	No highlights	Point 1	Point 2	Point 3	Point 4
f/6.3	1/1000	1/13	1/50	1/80	1/80
f/14	1/250	1/2	1/10	1/15	1/15
f/22	1/100	1/1.3	1/4	1/6	1/6

The yellow shaded column gives the exposure values at which there were no highlights showing on the piece of paper. The other columns show the values taken, from the specific areas of the photograph, using the cameras spot meter.

Using RAW to examine shadow detail

The image below shows the darkest area of the photograph lightened (exposure value of +2.85 in Photoshop) to show the fence panelling in the bamboos. It is very difficult to tell the difference between fence, bamboo and leaf.



Fence/bamboo shadow detail

Calculating the dynamic range of my D90

At f/6.3 exposure values from 1/13 through to 1/1000 giving 6.5 stops

At f/14 exposure values from 1/2 through to 1/250 giving 7 stops

At f/22 exposure values from 1/1.3 through to 1/100 giving 6.5 stops

According to the experts...

The forums differ in their opinions regarding the dynamic range of my camera, but it's somewhere between 7 and 9 fstops. Going by all the technical data presented on these websites I would guess that they applied a more rigorous set of test protocols than I did. I also suspect that it took them weeks to arrive at these results rather than a few hours. So all said and done I'm happy to accept that my results probably have a reasonable margin of error and that the dynamic range of my camera is between 7 and 9 fstops.