Highest Quality Capture: Workflow Phase I - Black and White in Photoshop CS4 and Photoshop Lightroom - page 38

shadow areas, degrading the quality with lost sharpness and an exponential
increase in grain but still of ering some information in the printing process.
With slide i lm on the other hand, it is very important to monitor overexposure
and the resulting loss of detail. Slides capture a much smaller brightness
range than negatives, and therefore require more careful exposure. In digital
capture, as with slides, overexposure resulting in blocked highlights is the
most common problem. Digital sensors are linear and have abrupt endpoints.
According to ISO measurements by Kodak, a digital sensor exposed for an
18% rel ectance gray card will saturate at 106% rel ectance (and reach a pixel
level 255 out of 255.) This can result in blocked highlights in contrasty scenes.
Many digital camera sensors reduce the severity of the blocking with built-in
tonal response “S” curves. These curves are applied when raw capture i les
are converted, but are not the i nal solution for perfect exposure in the i eld.
Digital photographers must still be ever vigilant in their attention to highlight
information when setting exposure.
Therefore, for the highest quality image capture, especially in extreme and
challenging lighting situations, raw capture is by far the best choice.
So what is the Zone system more specii cally?
In essence, the Zone system describes the range of tonalities from light to
dark, or pure white to pure black within an image. Ansel Adams divided this
range of tonalities into 11 zones (0-X in Roman numerals), each zone being a
single f-stop or aperture setting apart. The middle gray value corresponding
to the 18% gray card is assigned to Zone V, and each of the remaining zones
as a one stop exposure increase or decrease from Zone V. With 0 being pure
black (black without detail), the darker tones were assigned lower zone
numbers. With Zone X corresponding to pure white (white without detail),
all the lighter tones were assigned higher zone numbers. Whereas the ends
of the scale II and IX will show only a bit of detail, III, IV,VI and VII will clearly
reveal subject detail and texture.
With the full range of tones established, Ansel Adams dei ned the dynamic
range as the i rst useful values with detail as Zone I-IX. Exposure latitude was
outlined as the range of values that a particular i lm (or now, digital sensor)