Winter Landscapes page 3

Above: I made some pictures “exposed (fully) to the right” – and could scarcely see a thing on the camera’s display. A more conventional exposure, with the histogram’s bell closer to mid point, yielded a better result.

Exposure Matters
One of the greatest advantages of shooting digitally is the ability to confirm the right exposure at the time of shooting rather than days later at a light table. But notions of what is “right” are a little vague. The exposure that looks right on the camera’s monitor is almost certainly not the best one. The “right” exposure for a JPEG file is not necessarily the same as for the RAW version. And as for what the camera’s own meter suggests – that is often little more than a starting off point anyway.

A digital camera records light  quite differently from film – or our eyes. In its linear response to light, twice as many photons make the image twice as bright. Since a 12 bit digital camera can record 4096 levels of brightness between pure black (0) and pure white (255), it follows that half the total number of levels (2048) are represented in the brightest stop. Conversely, the darkest stop has only 64 levels  “expressions of difference”. What this means in practice is that if you underexpose an image, you have many fewer levels to remap over the width of the histogram from highlight to shadow than if you “ expose to the right” of the histogram. Underexposed pictures, once processed, exhibit exaggerated noise and poor tonal gradation.

Expose to the right and your image may look too bright on the camera’s monitor, but you are assured that you are starting off with as much data as possible. Your guiding principle should be the preservation in at least one colour channel of detail in the most important highlights in the picture. Cameras tend to be conservative and blinking highlights may in fact be fine when the picture is in the RAW converter.

 It’s clear that the histogram, rather than the camera meter’s readout, is the point of final reference and for this reason I’d recommend you keep things simple – and exposure more consistent – by using manual exposure mode and learning where best to meter the scene in centre-weighted or spot mode, for the best approximation of good exposure.

Right: Not only does the surf and spray contrast better with a dark sky emphasises the menace of these enormous waves racing toeards the shore

Blow-out
Worried that you’ve lost vital highlights ? Then, if your camera permits, view the individual colour channels; often highly saturated colours will blow out a single channel but detail in one other is all you need. Be pragmatic, too, about how far you should go to save highlights; try to keep detail in sparkling water or a sun-lit ice and you’ll end up underexposing the rest of the picture so severely that you’ll have too little data to map for smooth and detailed shadow areas. If the highlights are not important – or you are specifically after a “high key” look - then just let them go.