Exercise 7: Your tolerance towards noise

Brief: Set your camera on a tripod. Take a series of identical pictures, changing the ISO setting from one to the next. Avoid exposures more than 1/2 second and cover the whole range of ISO settings available and note the results.

ISO 100, 21mm, f/9.5, 0.30000s

For this exercise I used flowers as the subject due to the variety of textures on the leaves and petals.

ISO 100, f/9.5, 0.3s

ISO 100, f/9.5, 0.3

ISO 200, f/9.5, 1/6

ISO 200, f/9.5, 1/6

ISO 320, f/9.5, 1/10s

ISO 400, f/9.5, 1/10s
ISO 400, f/9.5, 1/10

ISO 500, f/9.5, 1/15s

ISO 500, f/9.5, 1/15

ISO 640, f/9.5, 1/20s

ISO 640, f/9.5, 1/20

ISO 800, f/9.5, 1/20

ISO 800, f/9.5, 1/20

ISO 1000, f/9.5, 1/30

ISO 1000, f/9.5, 1/30

ISO 1250, f/9.5, 1/45s

ISO 1250, f/9.5, 1/45

ISO 1600, f/9.5, 1/60

ISO 1600, f/9.5, 1/60

ISO 2000, f/9.5, 1/90

ISO 2000, f/9.5, 1/90

ISO 2500, f/9.5, 1/125s

ISO 2500, f/9.5, 1/125

ISO 3200, f/9.5, 1/180

ISO 3200, f/9.5, 1/180

ISO 4000, f/9.5, 1/250

ISO 4000, f/9.5, 1/250

ISO 5000, f/9.5, 1/250

ISO 5000, f/9.5, 1/250

ISO 6400,f/9.5, 1/350

ISO 6400,f/9.5, 1/350

Before looking at the affect that the ISO has on image quality it is clear from the camera’s EXIF information it is clear that as the ISO increases so does the shutter speed. Therefore there are obvious advantages to increasing the ISO when wanting to freeze the action in darker settings.

From the images above, which are viewed at 100%, it is clear that the image quality starts to become noisy at around ISO 1600. The leaves appear grainy and speckled. This decline in image quality continues as the ISO increases up to the 7D maximum of ISO 6400.

This exercise has enabled me to get to know my camera better and to be aware of it’s limitations. In lighting conditions similar to the scene above I can use an ISO of up to 1600 before any noticeable loss in image quality. This will enable me to be more creative when wanting to use different aperture sizes and shutter speeds.

Luckily for me, and as demonstrated by this exercise, the Canon 7D has a very good noise tolerance. Norman Koren has produced an Imatest analysis program for quantitative, thoroughly objective analysis of digicam test images. Below are ‘noise analysis’ graphs for the Canon 7D.

Canon 7D Noise Analysis

Canon 7D Noise Analysis

The Canon 7D does a good job at keeping luminance noise (indicated by the black line) at higher frequencies, though the slope of the luminance plot isn’t quite as flat as some other cameras in its category, including the Canon 50D and the Nikon D300S. The result is a fine noise “grain” that is slightly visible at ISO 100, when pixel peeping at deeper mid-tones and shadows. Still, this is very good performance, considering the 7D’s higher than average pixel count. Like many cameras these days, the chrominance channels (especially red) have higher noise levels at lower frequencies, though the 7D’s chroma noise at low ISOs much better controlled than its predecessor, the 50D.

Source: http://www.imaging-resource.com/PRODS/E7D/E7DIMATEST.HTM

 

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