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84<p class="text-center"><a href="motion-picture.html#log">Log Format</a> • <a href="motion-picture.html#properties">DPX Properties</a> • <a href="motion-picture.html#settings">DPX Settings</a></p>
85
86<p class="lead magick-description">DPX (SMPTE 268M-2003) - This format is used in Motion Picture and Effects industry that makes particular use of the extensive header information and the format's flexibility in being able to handle high dynamic range and logarithmic color values at a variety of bit depths using RGB or YCbCr pixel descriptions.  It is based on, but largely supersedes, Kodak's Cineon format that has more a more film specific header.</p>
87
88<p>One example of it's use includes scanning film for use in post production. Each frame is stored as an individual DPX file ranging from 2k (2048 pixels wide) to 8k (8192 pixels wide - for IMAX frames) at anything between 8 to 64 bits per color component. A sequence of these might then be processed using compositing software, altering the color or adding visual effects. Once complete they might then be recorded digitally to tape or projected back on to film.</p>
89
90<p>The color values for each pixel are often stored logarithmically (particularly if the sequence is destined to be transferred back on to film) which more naturally reflects the density of how color information is stored in the emulsion on the original film. When viewed without alteration, logarithmic files appear to have very low contrast and requires a 'look up table' to translate the logarithmic image to something that resembles what you might see if the image was transferred back to film and projected in a cinema. Apart from making the image linear (like most typical computer images) and adjusting the gamma level this table sets where the black and white point lies.</p>
91
92<p>For a 10 bit logarithmic image where each color component value ranges from 0 to 1023 the black and white points are normally set at 95 for black and 685 for white. What this means is that the logarithmic file stores color values that are lighter than what the linear version will display as pure white and darker than what it will display as pure black. This extra information therefore remains available for an effects artists who might wish to alter the brightness of the image after it has been stored as a DPX file.</p>
93
94<p>As an example, had this information been lost, reducing the brightness of an image uniformly would result in highlights becoming darker, whereas with this extra information the highlights instead reduce in size and start showing details that were previously too bright to be seen. The latter is far closer to what happens in the real world.</p>
95
96<p>The header can contain Film and/or Television specific data related to a production. For example the television header can contain a SMPTE time code so that shots exported as a DPX sequence from a production's edit can be easily replaced once any effects have been added. The film header holds information about the reel of film the frames originated from and various camera settings that were used while filming.  All these details usually stay with the images as they are passed between post-production companies.</p>
97
98<h2><a class="anchor" id="log"></a>Log Format</h2>
99
100<p>The color values for each pixel are often stored logarithmically (particularly if the sequence is destined to be transferred back on to film) which more naturally reflects the density of how color information is stored in the emulsion on the original film. When viewed without alteration logarithmic files appear to have very low contrast (leftmost image), and so require a 'look up table' to translate the logarithmic image to something that resembles what you might see if the image was transferred back to film and projected in a cinema (rightmost image). Apart from making the image linear (like most typical computer images) and adjusting the gamma level this table sets where the black and white point lies.</p>
101
102<ul>
103  <a href="../images/bluebells_log.jpg"><img src="../images/bluebells_log.jpg" width="384" height="288" class="image-slices" alt="bluebells-log" /></a>
104  <a href="../images/bluebells_lin.jpg"><img src="../images/bluebells_lin.jpg" width="384" height="288" class="image-slices" alt="bluebells-linear" /></a>
105</ul>
106
107<p>For a 10 bit logarithmic image where each color component value ranges from 0 to 1023 the black and white points are normally set at 95 for black and 685 for white. What this means is that the logarithmic file stores color values that are lighter than what the linear version will display as pure white and darker than what it will display as pure black. This extra information therefore remains available for an effects artists who might wish to alter the brightness of the image after it has been stored as a DPX file.</p>
108
109<p>As an example, had this information been lost, reducing the brightness of a linear image uniformly would result in highlights becoming darker (leftmost image), whereas with this extra information the highlights instead reduce in size and start showing details that were previously too bright to be seen (rightmost image). The latter is far closer to what happens in the real world.</p>
110
111<ul>
112  <a href="../images/bluebells_clipped.jpg"><img src="../images/bluebells_clipped.jpg" width="384" height="288" class="image-slices" alt="bluebells-clipped" /></a>
113  <a href="../images/bluebells_darker.jpg"><img src="../images/bluebells_darker.jpg" width="384" height="288" class="image-slices" alt="bluebells-darker" /></a>
114</ul>
115
116<h2><a class="anchor" id="properties"></a>DPX Properties</h2>
117
118<p>ImageMagick supports these DPX properties:</p>
119
120<pre class="pre-scrollable"><code>dpx:file.copyright
121dpx:file.creator
122dpx:file.filename
123dpx:file.project
124dpx:file.version
125dpx:film.count
126dpx:film.format
127dpx:film.frame_id
128dpx:film.frame_position
129dpx:film.frame_rate
130dpx:film.held_count
131dpx:film.id
132dpx:film.offset
133dpx:film.prefix
134dpx:film.sequence_length
135dpx:film.shutter_angle
136dpx:film.slate
137dpx:film.type
138dpx:orientation.aspect_ratio
139dpx:orientation.border
140dpx:orientation.device
141dpx:orientation.filename
142dpx:orientation.serial
143dpx:orientation.x_center
144dpx:orientation.x_offset
145dpx:orientation.x_size
146dpx:orientation.y_center
147dpx:orientation.y_offset
148dpx:orientation.y_size
149dpx:television.black_gain
150dpx:television.black_level
151dpx:television.break_point
152dpx:television.field_number
153dpx:television.frame_rate
154dpx:television.gamma
155dpx:television.integration_times
156dpx:television.interlace
157dpx:television.padding
158dpx:television.time.code
159dpx:television.time_offset
160dpx:television.user.bits
161dpx:television.vertical_sample_rate
162dpx:television.video_signal
163dpx:television.white_level
164dpx:user.id
165dpx:user.data
166</code></pre>
167
168<p>Look for any user data as the <code>dpx:user-data</code> image profile.</p>
169
170<p> To determine which properties are associated with your DPX image, use this command for example:</p>
171
172<pre class="highlight"><code>identify -verbose bluebells.dpx
173</code></pre>
174
175<p>To identify a particular property, try this:</p>
176
177<pre class="highlight"><code>identify -format "%[dpx:television.time.code]" bluebells.dpx
178</code></pre>
179
180<p>Finally, to set a property:</p>
181
182<pre class="highlight"><code>convert bluebells.dpx -define dpx:television.time.code=10:00:02:15 bluebells-001.dpx
183</code></pre>
184
185<h2><a class="anchor" id="settings"></a>DPX Settings</h2>
186
187<p>Use <a href="command-line-options.html#set">-set</a> to specify the image or film gamma or black and white points.  For example use:
188</p>
189
190<pre class="highlight"><code>-set gamma 1.7
191-set film-gamma 0.6
192-set reference-black 95
193-set reference-white 685
194-set profile dpx:user.data
195</code></pre>
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