Winter in Italy

By all accounts this weekend is to be the last before the weather turns colder and wetter as winter approaches Ireland. In some respects we are lucky that our winters are not as severe as other places, though the occassional snow fall can be a welcome change from the usual “rain, clearing to showers” forecast that becomes all to common this time of year.  We are unlikely, however, to see a snowfall like they get in the skiing resort of Sauze D’Oulx in the Italian Alps, where today’s image was taken.

The shot, taken in early 2008 during a skiing trip with friends, is a view from our apartment on the outskirts of the resort, which is itself not too far from Turin.  It’s also a good example of two reasons to use a digital SLR camera in RAW mode rather than in JPEG mode.

Although I shoot in RAW 100% of the time these days,  this shot was taken in JPEG mode.  And had I shot it in RAW mode, it would be a better image.

The first reason to shoot in RAW mode is white balance.  White balance is basically the way you calibrate your camera sensor to interpret the range of colours in the scene to compensate for the colour temperature of the light falling on the scene, so that whites stay white, greys stay grey, and blacks stay black.  For instance, if you take a photograph indoors at night, using your room lights to light the scene, the light has a warm tone from those tungsten lightbulbs.  If you take a shot outdoors on a cloudy day, the light will have a cool tone.  Put a white subject in both those scenes, and if you want it to stay white in the final image, you need to communicate to the camera that the light sources are different temperatures.  The way you do this with a digital SLR camera is by setting the white balance appropriately – e.g. to tungsten for the first shot, to cloudy for the second.  This then adjusts how the camera processes the colours to keep the white subject white in the final image.

Or at least that’s what happens when you shoot in JPEG mode.  And once that compensation is applied, in JPEG mode it is very difficult to change it without compromising image quality.   Cameras provide a means for JPEG shooters to not have to worry about this too much by including an Automatic White Balance mode, but, like all automatic modes on a camera, it is not fool proof.  It works by using the camera’s metering system to make an educated guess as to the colour temperature of the scene.  But the system can get confused. One particular culprit for confusing the automatic white balance calculation is snow.  I’m not entirely sure why this is, but I suspect the sheer volume of white in a snowy scene just upsets some assumptions the camera makes and it misinterprets the scene.  Typically you will see a picture of a snowy landscape reproduce with a noticeably blue tint.

If you shoot in RAW however, because the camera applies almost no processing to the image, you can change the white balance in post production with no loss in image quality whatsoever.   Because of this, even if you usually shoot in JPEG mode, if you find yourself photographing snowy scenes, give some consideration to trying out RAW.  For the shot above I manually adjusted the white balance to keep the snow white because I was aware of the issue, but taking it in RAW mode would have been a better option.

The other (probably bigger) reason to shoot in RAW mode is that the image retains more information (it’s a bigger file) and so you can recover detail from the extreme areas of the exposure, and particularly from the highlights.  It’s all to do with how different levels of exposure map into the 12-bits of information stored per colour channel, per pixel.  The mathematics aren’t important – what is important is that with a RAW file it is possible to adjust the exposure by up to two stops in each direction after you’ve taken the shot.

As well as doing wholescale adustments to the exposure however, most RAW processors (like Aperture, which I use) will allow to to make local adjustments, and recover detail in the highlight or shadow areas of the frame.

If you look at the bottom left corner of the shot above you’ll notice that it is pure white.  (Actually, there’s a very slight sepia tone applied in post-processing for this shot, so it’s acutally pure very light beige).  Had I shot it in RAW mode I could, more than likely, recovered detail in this area of the frame and avoided that blown-out effect.  At least I got the white balance correct, I suppose.