Sunday, 12 May 2013

Dynamic range impressions

Concerning dynamic range I have been reading 'The Digital SLR Handbook' by Michael Freeman (2011) and I can definitely relate to his ellusions to the importance of getting the exposure as close to your ideal brightness as possible, particularly when out photographing high contrast scenes. I found this useful to remember; not just because there is less post processing, thus resulting in more time to take more photos, but often because extra extraneous post processing such as HDR processing simply isn't necessary. This lack of need for extra processing is partly due to DSLR's (in my eyes) massive dynamic range within the limits of an informed exposure but also because it is further increased by shooting in the raw format.

   I thought it was important to be aware that an informed exposure was 'not necessarily the same thing as getting it averaged' - M. Freeman (2011). The reason I felt it was important was because shadow areas held more detail than the highlights - in a typical raw capture you could 'expect to be able to adjust the original exposure by up to 2 stops darker and 4 stops lighter' - M. Freeman (2011). This meant shadow areas were more responsive than highlights in terms of retaining detail later.
Figure 1 - jpeg version (including histogram)

   These raw exposures captured with ideal brightness when processed - even quickly - can produce images with, for me, dynamic range approaching HDR images' dynamic range. For example, in this handheld, high-contrast shot (Figure 1), I tried as suggested in 'The Digital SLR Handbook' (2011) to assess the scene and take a photo where I was 'on guard against clipped highlights' - M. Freeman (2011). There was sufficient dynamic range in my Sony A57 DSLT camera to later process the raw file with, of course, no highlight clipping but also very little shadow detail lost. I did this by simply dragging the 'whites' and 'highlight' sliders to the left and the blacks and shadows sliders to the right quite strongly within Adobe Camera Raw 7.1 (Figure 2).

Figure 2 - raw version (including histogramwithin Adobe Camera RAW 7.1)
   As can be seen in Figure 1, areas of extreme shadow in the equivalent jpeg image (I shot the image in raw+jpeg format) were mostly black and highlights appeared 'washed-out'. On the other hand, highlights in the raw version (Figure 2) were still rich in colour, while shadows could be 'opened up', without much penalty of noise. I had discovered noise could be a problem when shadow areas were brightened in the 'your tolerance for noise' exercise. I perhaps went to the extremes of the 'shadows' and 'blacks' sliders a bit too much in the example photograph, although it was just to show the scope of the camera's dynamic range. I was therefore eager to find a practical measurement of my camera's dynamic range within the course in case I needed to make a judgement on how best to capture a very high contrast scene.
Photograph 1 - raw edited version where converging verticals and barrel disortion were corrected

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