Exercise – Higher and lower sensitivity

In an effort to get through the lighting exercises in a reasonable time (there are a lot of them) I’ve lowered my personal quality control and included the pictures below. While the images are throw-away, they demonstrate the theories I set out to.

On my walk to work this morning, I spotted this arrangement that contained both movement (in the wind turbine blades) and some fairly deep shadow on the right side of the telegraph pole. I used the x100 and set the aperture to f/16. That meant that as I changed the ISO setting, the shutter speed would change automatically.

Because it was a bright, July morning I engaged the camera’s in-build ND filter to allow a slow enough shutter speed to see movement in the blades at ISO200. That was the starting point as I moved up through the range 200, 400, 1000, 1600, 3200 and 6400.

The pictures to the right show a detail of the main image, enlarged to 100%.

The ISO200 shot was taken at 1/8th of a second and as you might expect, it wasn’t possible to get an acceptable image with the camera hand-held.

At ISO400 and 1/18s, the image is acceptable (the benefits of a lightweight, compact camera). There is good detail throughout, a full histogram and detail in the shadows.

At ISO 6400, the shutter speed has reduced to 1/250s, freezing any movement in the turbine. This is at the expense of detail, particularly in the shadows. The detail has been replaced with unattractive digital noise – not a problem when viewed on a screen at these sizes, but it would be if printed or enlarged.

The exercise shows that we should keep our options open and use higher ISOs if it allows us to get the shot we need, particularly if the final use of the image allows.

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