Friday, August 31, 2012

Proper Exposure Matters!

Text And Photography By George Jardine Published in Advanced Camera Technique
There are differences between the way film responds to quantities of light and how a digital sensor responds. The Zone System was devised to create a method for photographers to accurately predict how various tones within a scene would translate to the photographic image. By understanding how to reconcile the differences between digital and analog photography, we can use the Zone System just as effectively today.
There are differences between the way film responds to quantities of light and how a digital sensor responds. The Zone System was devised to create a method for photographers to accurately predict how various tones within a scene would translate to the photographic image. By understanding how to reconcile the differences between digital and analog photography, we can use the Zone System just as effectively today.
The first thing you probably notice is how compressed the tonal range is, especially in the shadows. The 5D Mark II is showing only about 7 stops of useful dynamic range here, and the lower shadow values are stacked up very close together.

Fig. 7

Turning to the new 2012 Process Version, we find that EV 11 with more than one full stop of exposure (1⁄2 sec. at ƒ/5.6) falls at 99.9%, which then yields these values (Fig. 7).

The difference is pretty dramatic and points to several notable improvements. First, the entire range expands out across 11 EVs, which causes the top five steps to much more closely resemble the top five values in Adams' Zone System. The lower five steps still show less differentiation than on the Zone System scale, but these last three steps at least now have usable values.

Highlight rendering has changed considerably, with the top two stops of exposure being compressed into just 9% of your top tones—9% in Lightroom's gamma-encoded 0 to 100 scale, which could represent as much as 75% of your total gray levels in the capture's linear 14-bit space! Compared to the 2010 process where the top two stops of exposure account for fully 30% of your gamma-encoded tones, the new process produces a much more "film-like" transition into white, with many more available tones to play with.

These results convinced me of two things. First, more than ever, proper exposure is paramount with digital. Placing your maximum white value as high up in the exposure as possible ensures that you'll have the most bits to play with and the greatest possible separation in the midtones. Second, I clearly would have to start carrying my spot meter with me everywhere as a standard part of my camera kit.

So now that you know where your tones are going to fall in Lightroom, what are you going to do with that? In my next installment of this two-part series, we'll look at just that, with a fun analysis of how to use highlights with whites and shadows with blacks in the new 2012 Process Version.

See more of George Jardine's photography, read his blog and check out his Adobe Lightroom tutorial videos at www.mulita.com.

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