Blown highlight

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A blown highlight is an area of pure white on the negative, print or digital image, where there is thus no texture and no differentiation. Blown highlights often exhibit posterisation as they transition to other values. Generally speaking, blown highlights are to be avoided. They are relatively recoverable on film, somewhat recoverable when shooting in digital raw, and not recoverable in files which are 8 bit in depth or less, such as most JPEGs.

The rear display of most Nikon digital cameras can be set to reveal blown highlights.

Blown highlights are easily identifiable using the histogram, as they are shown by a stack of values on the extreme right edge.

In this histogram, the stack of values on the right (the very thin, tall line) can be clearly seen.

Sometimes, blowing the highlight can be used creatively. In this histogram, below, you see a range of values gradually building up to a large area of pure white. If you want to create images this way, it's important to inspect them very carefully to ensure there is no banding or posterisation. Display on a computer screen is considerably more forgiving of this than a print.

Here is the image that produced that histogram:

An image using a blown highlight as a background, which is now very popular in portrait photography, will always have the tell-tale stack of values on the right. This works very well, because the transition between other values and white is deliberately discontinuous, giving maximum contrast, and with no risk of banding.

If you want to create hot spots as a tool in composition to draw the eye, the histogram should ending up something like this:

In this image, the hot spots are round the edge of the leaf, below, but have been pegged a little below the maximum value, to allow a smooth gradation to the very highest values. Again, careful inspection of the image is needed to ensure that posterisation is not taking place.