The remit was to take an image indoors using daylight, the image had to contain a combination of sharp detail and textureless areas, with some of the textureless area in shadow.
The camera was set on a tripod and using the AV setting a series of shots were taken using ISO 100 through to ISO 1600. The cream wall has no features, whilst the wooden vase and Russian dolls provide both texture, detail, colour and shadow against the wall. I shot at f5.6 so that the images were not too under-exposed or I did not incur overly long shutter speeds.
None of the following images were processed so that the true impact of the ISO adjustments can be seen.
|ISO100 Shadow and detail|
|ISO200 Shadow and detail|
|ISO400 Shadow and detail|
|ISO800 Shadow and detail|
|ISO1600 Shadow and detail|
With exposure increased in raw the coloured artifacts become more noticable.
At ISO1600 the noise is very apparent and does not make for a very satisfactory image at all. Depending on what people are trying to capture sometimes it is better to obtain the shot than have no record whatsoever. Sometimes a little grain can add interest to an image especially if the image is converted to monochrome so the discolouration is less obvious.
The conclusion reached is that at a push I personally would not try to use a higher ISO than 800, but possibly would use 1600 if I desperately wanted to capture a specific event. The 400D seems to manage fairly well up to ISO400.