Take similar shots at both normal and high sensitivity (ISO). Shoot first at normal sensitivity, then change to higher sensitivity. Note whether the change make shooting easier. In particular, note whether there were photographs that you could not take successfully at the lower sensitivity but were possible at the higher setting.
Shooting handheld, trying to get a sharp shot of these berries at ISO 200 proved to be a bit difficult. The ISO 800 shot looks sharper, without too much noise evident.
The weave of the hat is much more evident in the higher ISO version. However, looking at the background there is a fair amount of noise visible.
In this street shot where there was a fair amount of movement, the low ISO shot gave far too much blur. Increasing to ISO 800 allowed the faces to be in focus. A little noise is creeping in, but the higher ISO shot is clearly a sharper capture.
For the remaining shots I tried to see how low and high ISO coped with decreasing light. This particular shot was taken at night, through the window of a vintage car showroom that for some bizarre reason has a dalek on display. The ISO 100 shot looks OK at a small size but when you zoom in to 100% the blur is visible. In this instance I went for an extreme change in ISO, right up to 3200. The effect is clear: the higher ISO allowed a much quicker shutter speed and less movement blur. However, the noise is heavy enough to spoil the shot. In a real shooting situation the best compromise might have been been in the ISO 800 – 1600 range.
Early evening outside a train station, and even though there was some ambient street lighting, the ISO 100 shot is blurry; the aperture was as wide as possible but the shutter speed was too slow to freeze any motion. The ISO 1600 version allows for a quicker and therefore a slightly sharper capture – but the shadows are looking fairly noisy. Overall, the higher ISO shot is more acceptable.
Probably the darkest scene I shot, and again I chose quite extreme low and high ISO settings. At ISO 100 the scene is far too blurry, even when viewed small. By cranking it up to ISO 3200 it’s possible to clearly make out the text on the diversion sign, although the flat surfaces – the sky, the road – are extremely speckled.
What I’ve learned:
Another eye-opener of an exercise. Up until now I’ve tended to try to stick to low ISO as I know that this will, in the right light circumstances, give the best quality image. What this exercise has brought home is that in the right circumstances it can be advisable to increase the ISO to make best use of low light and/or to allow faster shutter speed. Interestingly, I had to increase the ISO quite a bit on some of these to demonstrate (exaggerate) the effect. I believe modern digital cameras are better able to cope with reducing noise at higher ISOs. I do now have a better appreciation of how ISO can be used in marginal situations to achieve the desired exposure. Going forward I think I’ll probably treat it as a third option for adjustment, if I can’t achieve the desired effect by adjusting shutter speed and aperture.