Latitude


Image sensors are capable of recording a limited tonal range or brightness range. A subject photographed in high contrast lighting may exceed this recordable or ‘dynamic range’. The ability for the image sensor to accommodate a brightness range is referred to as its ‘latitude’.
Digital image sensors capturing JPEG images typically capture a brightness range of only 32:1 or five stops. It is essential for digital photographers to understand that when capturing JPEG images with directional sunlight, shadow and highlight detail may be lost. The photographer capturing RAW files has increased flexibility to capture a broader range of tones and with careful exposure, post-production processing and printing techniques they can extend this range dramatically. 


Previsualization

Awareness of the subject brightness range and the capability of the photographic medium to capture this range of tones, allows the photographer to previsualize or predict the outcome of the final image. When the brightness range exceeds the sensor’s capabilities the photographer has the option to increase or decrease exposure to protect shadow or highlight detail that would otherwise not record or switch to RAW capture when using a DSLR. These scenes are described as ‘extreme contrast’. 


Extreme contrast

In an attempt to previsualize the final outcome of a contrasty scene with a high brightness range, many photographers use the technique of squinting or narrowing the eyes to view the scene. This removes detail from shadows and makes the highlights stand out from the overall general scene. In this way the photographer is kind of able to guess the contrast of the resulting image terms of photography. If the photographer fails to take into account the image sensor’s limited capabilities both shadow detail and highlight detail can be lost, when there is a huge difference between the two extremes. Its better to protect the highlight detail in the exposure and fill the shadow detail with additional lighting if possible. Taking an average of the two extreme readings does not help as you may not get detail in either of the extremes. If one area needs an exposure of f 2.8 and the other one f 32, this does not mean that setting the camera at around f8 will justify the extremes but you will end up not getting detail in any area. One needs to understand which area has the focus of interest. What would the eye want to see. What do you want to show in the photograph ? Detail in dark areas with washed out highlights or detail in the brighter areas with deep dark shadows. Generally, shadows are always preferred compared to washed out highlights. Darker areas are more forgiving and one can recover some detail in these areas though RAW convertors and other editing softwares but detail lost in highlights cannot be recovered at all.  

 

In many situations when you are expected to work quickly, you simply notice the extreme brightness range and make quick judgements from experience to alter the exposure. This experience will come from your everyday observation of light in day to day situations in life. More you observe, more you will develop the sense of understanding light and contrast and its impact on the sensor.

A good understanding of your camera's exposure meter is very important. Its not really the same as it was several years back and there has been a lot of research and development in this area. While the exposure meter can still be fooled but the interpretations are certainly much better than the earlier times. The TTL metering is linked to the focusing point selected and obviously you will focus on the main subject, which will be rendered with correct focus. However, with a good understanding of your camera's behaviour ( yes, different camera brands and models may react differently to different situations ) you should know when to override the metering suggested by the camera.

This average exposure may not be suitable if the subject or detail is located in the deep shadows or bright highlights. In these instances the photographer must override the exposure indicated by the meter and either open up (increase exposure) if shadow detail is required, or stop down (decrease exposure) if highlight detail is required.

Few things to keep in mind-

You can alway use external light sources like a strobe /flash, a continuos fill light depending upon the situation to bring up the exposure in darker areas. On the other hand a neutral graduated filter may be added to reduce the exposure from the brighter area.

Shoot in RAW and not JPEG. RAW has a much larger ability to retain detail in extremes compared to jpeg. You can pull up the detail in shadows and highlights with the very basic RAW convertor.

You can also create two different layers, one justifying the highlights and the other justifying the shadows and sandwich them to bring out the best of the two.

Do not further increase the contrast in your camera settings. Do not reduce it bellow