Highlight clipping

One of the negative effects of the linear way in collecting light is that at the brightest end there is a point where the tones go pure white.  Our eyes don't see this and if you've worked with film you won't have experienced it to the same extent as with the digital sensor.

When I first started shooting with my dslr I found that I had problems with the sky in a lot of my shots.  Unless the sky was a bright, clear blue which is a bit or a rarity, I would have a pure white sky with patches of light grey.  Underexposing the shot can help with this but the sensor will still tend to over-expose the bright areas.  This is known as highlight clipping.

As a response to this I set the highlight clipping warning on my camera so now when I take a shot if there are any areas of blown out highlights I see a flashing light (blinkies) in that area on my LCD display.

Although we should try to avoid the 'blinkies' there are times when you have to decide what impact they have on your shot.  If there is a small area of blown out highlights in your image and it does not take away from the main subject then you can decide to leave them alone.  On the other hand if over a third of your image is blown out as in my examples with the skies then you need to adjust and shoot again.

This is a case where bracketing can help.  If you simply adjust your exposure for the sky to ensure it is not over exposed then you run the risk of having your foreground too dark.  By bracketing you can take one shot but at different exposure settings.  For example, the images could be one as the meter sees it, 1 stop under and 1 stop over.  These can be adjusted in photoshop later so you can brighten up the darker areas or darken the lighter areas depending on your shot.