Histogram - Seitz roundshot Instruction Manual

3.1.7 Histogram

The „Histogram" is an important tool to determine the quality of the exposure. When
the image is perfectly exposed, the histogram shows an evenly distributed light
frequency with no cropping of light at the borders like pictured above.
The x-axis of the graph shows the light levels (in DNs) and the y-axis the frequency of
these light levels in the image. It groups the DNs in classes (for example, 0-100 DN,
101-200 DN, 201-300 DN..., 15'901 – 16'000 DN) and then plots the frequency of
these classes (how many times these light levels are observed in the image) on the y-
axis to show the statistical distribution.
Underexposing the image is less problematic than overexposing it. An
underexposed image (for example by 1 f-stop) can quite easily be
brightened or tone-mapped in post-production (with often better
dynamic range), whereas darkening an overexposed image does not
lead to the same results (information in bright areas is cropped).
Instruction Manual Seitz 6x17 Digital - version 4.05 - May 2013- © by Seitz Phototechnik AG / Switzerland www.roundshot.ch
The „Histogram" is displayed with the image and shows
the distribution of light from the very dark to the very
light parts (in DNs) of the image.
When the image is underexposed, the histogram
values are situated on the left of the graph, i.e. most of
the light frequency is distributed in low DN levels.
Create a longer exposure or open the aperture.
When the image is overexposed, the histogram values
are situated on the right of the graph, i.e. most of the
light frequency is distributed in high DN levels.
Create a faster exposure or close the aperture.
When the exposure of the image is cropped, the
histogram becomes very flat. This happens when some
extreme values are located below the minimum (0) or
above the maximum (255). Adjust the exposure speed
or the aperture until the cropping disappears.
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