Recording to Blackmagic RAW
Blackmagic RAW works in 2 different ways. You have a choice to use either the constant bitrate
codec, or the constant quality codec.
The constant bitrate codec works in a similar way to most codecs. It tries to keep the data rate
at a consistent level and won’t let the data rate go too high. This means even if you are shooting
a complex image that might need a bit more data to store the image, a constant bitrate codec
will just compress the image harder to make sure the images fit within the space allocated.
This can be fine for video codecs, however when shooting Blackmagic RAW you really want to
ensure the quality is predictable. What would happen if the images you were shooting needed
more data, but the codec just compresses harder to make a specified data rate? It’s possible
you could lose quality, but not be sure it’s happening until you return from a shoot.
To solve this problem, Blackmagic RAW also has an alternative codec choice called constant
quality. This codec is technically called a variable bitrate codec, but what it’s really doing is
allowing the size of the file to grow if your images need extra data. There is no upper limit on
the file size if you need to encode an image but maintain quality.
So Blackmagic RAW set to the constant quality setting will just let the file grow as big as
it needs to be to encode your images. It also means the files could be larger or smaller
depending on what you are shooting. I guess if you leave your lens cap on the lens, you won’t
waste space on your media!
It is also worth noting that the quality settings for Blackmagic RAW are not obscure names, but
are more meaningful as they are derived from what’s happening technically. So for example
when you have selected the constant bitrate codec, you will see quality settings of 3:1, 5:1, 8:1
and 12:1. These are the ratios of the uncompressed RAW file size vs the file sizes you should
expect when shooting in Blackmagic RAW. 3:1 is better quality as the file is larger, while 12:1
is the smallest file size with the lowest quality. Many users of Blackmagic RAW find that 12:1
has been perfectly ok and they have not seen any quality limitations. However it’s best to
experiment and try various settings for yourself.
When using Blackmagic RAW in constant quality, the options are Q0, Q1, Q3 and Q5. These are
the compression parameters passed to the codec and they are setting how much compression
is applied in a more technical way. This setting is different because the codec operates
differently between constant bitrate vs constant quality. In this constant quality setting, you
really cannot tell what the file size ratio will become as it varies a lot based on what you are
shooting. So in this case the setting is different and the file will become the size needed to
store your media.
Constant Bitrate Settings
The names for 3:1, 5:1, 8:1 and 12:1 represent the compression ratio. For example, 12:1
compression produces a file size roughly 12 times smaller than uncompressed RAW.
Constant Quality Settings
Q0 and Q5 refer to different levels of quantization. Q5 has a greater level of quantization but
offers a greatly improved data rate. As mentioned above, the constant quality setting can result
in files that grow and shrink quite a lot, depending on what you are shooting. This also means
it’s possible to shoot something and see the file size increase to beyond what your media
card can keep up with. It could result in dropped frames. However the benefit is that you can
instantly see if this happens on a shoot and then investigate your settings vs quality.
Blackmagic RAW Player
The Blackmagic RAW player included in your Blackmagic camera’s software installer is a
streamlined application for reviewing clips. Simply double click on a Blackmagic RAW file to
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