Find a scene that has a wide range of brightness - appears contrasty, in other words. Find the exposure setting at which the highlight clipping warning just appears.
For this exercise I decided to go out to the garden, the sun was shining and it seemed like a good option.
Clipping due to overexposure
Clipping can often occur in image highlights as a result of an incorrect exposure when initially photographing or scanning to a digital image. Increasing an exposure increases the amount of light collected or the sensitivity of the sensor, and increasing it too far will cause the lightest areas, such as the sky, or light sources, to clip.
Bright areas due to overexposure are sometimes called blown-out highlights or flared highlights. In extreme cases, the clipped area may appear to have a noticeable border between the clipped and non-clipped area. The clipped area will typically be completely white, though in the case that only one color channel has clipped, it may represent itself as an area of distorted color, such as an area of sky that is greener or yellower than it should be.
[online text] available from:
http://en.wikipedia.org/wiki/Clipping_(photography) [Accessed on: 21/09/12]
Image 1
1/160 f5.6 ISO 800
This image was taken mid afternoon in the garden. This was just outside of the highlight clipping areas.
Image 2
1/200 f5.6 ISO 800
The next 3 images were taken decreasing the exposure each time and clearly show the highlight areas ie the brighter areas of the images beginning to become washed out, these areas being the path, sky and sunlit areas.
Image 3
1/100 f5.6 ISO 800
Image 4
1/80 f5.6 ISO 800
Image 5
1/60 f5.6 ISO 800