Shooting outdoors means dealing with challenging and changing lighting conditions which can sometimes lead to blown out highlights in your images. ie. Groups of pixels in your image that are 100% white and show no detail. Taking the time to think about the way your camera is set up before heading out will help you to avoid having to deal with this common issue.
Learn You Camera's Metering Modes – if you haven't read the section of your camera's manual about metering then sit down and take it on board! Learning about the differences between the various metering modes (they are called different things by the various different manufacturers such as Evaluative, Matrix, Partial, Spot, Centre-weighted etc.) will ensure you are able to select the most appropriate mode depending on the circumstances.
Watch that Histogram – DSLRs will normally have a built in display that allows you to see a histogram showing the range of light captured in an image, typically with shadows shown on the left and highlight shown on the right.
As with most technical matters in photography, opinion varies on the best way to utilise the histogram – a lot of photographers and websites will tell you that the ‘best' way to ensure that your image is well exposed is to have a histogram that looks like a classic bell curve or mountain, whilst others will tell you that due to the nature of the way digital cameras capture light it is better to expose ‘towards the right', or towards the highlight end. This article from LightStalking's Jason Row explains the latter in greater detail and is well worth a read.
Use Your Camera's Blink Function – a simpler way to show over exposed highlights is to use a feature that the majority of DSLRs will have, the option to show over-exposed highlights as a blinking area on the image. This feature makes it very easy to spot where you have over exposed. Again, if you aren't sure how to activate or use this feature, consult the manual for the camera you are using.
Shoot RAW – if your camera has the ability to shoot RAW files then wherever possible use it – RAW files have a lot more leeway when it comes to clawing back highlights than JPG files.
Consider Using Filters – Gradual density filters can be used to balance the exposure of the sky and the rest of the scene. They are especially useful if you are shooting in the afternoon and there's a lot of light in the sky. Neutral density filters can be used to reduce the amount of general light in a scene and can be utilised where a scene is just too bright to capture normally. A good set of filters are a must if you intend on shooting outdoors regularly.
On the shot above the bright cloud in the sky would have been completely blown out if I hadn't used a gradual density filter.
Learn About Bracketing Your Shots – another alternative method to avoid blown out highlights is to use exposure bracketing – most DSLRs have this included (again, consult your manual if unsure or this site lists some commonly used cameras bracketing features), but if yours hasn't it's an easy feature to replicate manually. Exposure bracketing lets you capture the same scene with different exposures but with the same aperture and ISO.
By default, most DSLR cameras let you bracket -2 stop, 0 stop and +2 stop images. Or to look at it another way, an image that is underexposed, a ‘correctly' exposed image and an over exposed image. These images can then be manually imported and blended (using Photoshop or similar software capable of handling layer files) or combined into one file using the HDR (High Dynamic Range) method. Arguments about the aesthetic appeal of HDR can be found all over the internet – whatever your opinion of the final result, it's a good way to avoid blown out highlights.
As for out of camera work, stop and think about the circumstances of the shoot – if the light is too bright and harsh now, can you come back earlier or later in the day, or on a different day when the weather is different?
Do you have any tips for reducing highlights when shooting outdoors? Please share them in the comments below!