Your tolerance for noise

The exercise required taking a series of photographs indoors during daylight using a combination of sharp detail and textureless areas, with some of the texture in shadow, on each ISO setting available.  My camera Nikon D5000 has an ISO range of 100 to 6400.  In a previous similar exercise completed in TAOP, I found that in darker situations, noise started to be introduced at around 250, so I was interested to see in a lighter context what the results would be.  In practice, I rarely exceed ISO 200 if I can help it, unless I deliberately want to introduce grain, or if lighting conditions make it really necessary.  I used my prime lens for the photographs (focal length 35mm), allowing a faster shutter speed on a wider aperture.

1/10s  f/1.8  ISO 100

1/20s  f/1.8  ISO 200

1/30s  f/1.8  ISO 250

1/30s  f/1.8  ISO 300

1/45s  f/1.8  ISO 400

1/60s  f/1.8  ISO 500

1/60s  f/1.8  ISO 640

1/90s  f/1.8  ISO 800

1/125s  f/1.8  ISO 1000

1/125s  f/1.8  ISO 1250

1/180s  f/1.8  ISO 1600

1/180s  f/1.8  ISO 2000

1/250s  f/1.8  ISO 2500

1/350s  f/1.8  ISO 3200

1/750s  f/1.8  ISO 6400

As the results show below, with a pale coloured background, the noise started to appear around ISO 320 and by ISO 500 it was too much.  Even at the magnification of the images above, you can see noise by ISO 640 and obviously this continues to increase through to ISO 6400.  So even though my camera has the ability to use the higher ISO sensitivities, I don't think it is advisable unless you deliberately want noise.

In recent photographic memory, I have only taken one image where I felt the noise added to the image.  In this image, I think the noise in the sky adds some interesting speckles and texture in the top right corner as they meet the lines of the bridge, tree etc.

1/45s  f/3.3  ISO 2000