Update: 20th of March 2020; Added sections: 4k On-Set Monitoring
When working with a high end digital cinema camera like the Sony Venice, it is necessary to understand the color settings that affect the appearance of the image. This is important to be able to maintain consistent image results throughout the complete production process: On-set across multiple shooting days, as well as to achieve predictable image results in post production.
We collected some facts about the color settings of the Sony Venice that are helpful when working with this specific camera. The facts should help to enable you to configure the camera consistently across shooting days and transparently communicate the used settings to post production.
1. “Base ISO” and “Exposure Index (EI)”
Generally, the Sony Venice has two hardware circuits built in that allow the user to choose between two different native sensitivities of the sensor. In its menu the Sony Venice refers to the selection of those basic ISO values as “Base ISO”. This can either be 500 (which is the default for “normal” lighting conditions) or 2500, and can be set via Project > Basic Setting > Base ISO.
Additionally the user can set a sort of gain, which can be understood as a factor that is calculated onto the image and simulates a certain sensitivity. Inside the Sony Venice camera menu this is referred to as the “Exposure Index” or often referenced in the menu as “EI”.
Memorizing these two concepts and how the camera menu refers to them, we can move on talking about log signals and how Sony Venice handles exposure in conjunction with log.
2. “Log” vs. “SLog3”
Both of the above refer to a logarithmically encoded signal, which results in an image appearance that has little contrast and is actually not really intended to be viewed. Encoding the captured signal logarithmically is used across high-end camera manufacturers in order to store more signal information in the same signal data, and therefore improve the quality of the transported image.
With this idea of log in mind, let’s look at how Sony Venice deals with different flavors of such log signals:
In the Sony Venice the term “Log” refers to the logarithmically encoded signal without the Exposure Index (EI) factor applied. So no matter what the Exposure Index setting is, the “Log” output stays the same.
“SLog3″ however, is a special log flavor that has, and this is crucial, the Exposure Index applied.
This means that as long as the “Base ISO” and the “Exposure Index (EI)” are kept at equal value the image appearance is not different for “Log” and “SLog3”, but as soon as the “Exposure Index (EI)” changes, the “SLog3” takes it into account but the “Log” does not.
In the camera menu the “Log” output for the SDI can be directly selected as a color in the menu, however “SLog3” has to be configured as a “Look”.
As a side note: Keep in mind that there is also an additional flavor of “SLog3” available which is “SLog3.Cine”.
The topic of “Log” vs. “SLog3” becomes important when looking at the capabilities of the SDI outputs and what they are capable of concerning color settings.
3. Capabilities of Physical SDI Outputs
The SDI outputs of the Venice have different capabilities when it comes to selecting color settings.
The SDI Out “Monitor” and SDI Out “1/2” have limited capabilities and can only output a signal in Sony Venices “Log” (which means that the Exposure Index is not applied.)
As explained above, as long as Exposure Index is left at “Base ISO” the appearance does not differ from an “SLog3” signal. But as soon as the “Exposure Index” changes the image output set to “Log” will not take it into account for the image appearance.
The fact that the SDI outputs “Monitor” and “1/2” are limited to “Log” limits their flexibility.
SDI Out “3/4” however is capable of outputting “SLog3.Cine”, “SLog3”, “s709” or “R709” via selecting them as a “Look”. To set this up properly do the following:
- Set color space as intended in “Basic Project Settings”
- Go to the output color settings and to “Edit Look”
- Set “SGamut3/Slog3” as the “Preset Look” (see image below).
- Go to the “SDI 3/4” color settings and select “Look” as output.
Like this you can receive a log signal on the SDI out 3/4 that reacts to the change of the Exposure Index.
This becomes relevant when trying to match the SDI output of the Sony Venice to recorded clips:
A visual match can only be achieved when the fact that the Exposure Index is not always applied to the SDI out, is considered correctly: As the Exposure Index is mathematically added when displaying recorded clips in software, a visual match can only be achieved when using “SLog3” for the SDI output taking the “Exposure Index” into account for image appearance.
Please be aware of the fact that a visual match between HD-SDI out and recorded clip is also possible selecting a “Log” output from the camera, as long as the “Exposure Index” does not differ from the “Base ISO” for the SDI out, the clip however received an “SLog3” space. Be cautious: As this is the default of the camera you might notice too late if you set the SDI out up in “Log” and change the “Exposure Index” after some shots, and like this loose a visual match.
4k On-Set Monitoring
Monitoring in 4k resolution on set is possible in different configurations with the Sony Venice: Using 4x 3G SDI/BNC ports, but also 6G and 12G options are available using single BNC outputs.
However, all of the 4k monitoring options seem to share the same circumstance that the output color space options are limited to “Log (EI not applied)”. This will require you to stay either at “Base ISO” or at least be aware of the discussed facts above differentiating “Log” and “SLog3” or work yourself around it in a different way.
4. Legal vs. Full Range Signal Levels
Dealing with video level ranges relates to the color settings as both affect image appearance. It is important to look into that when working with the SDI output of Sony Venice, for example when applying a LUT via Livegrade.
The signal range of the SDI output from Sony Venice is generally “full range”, when looking at the “SLog3” output option via a “Look” (as described above). However it is important to understand that the Sony provided LUT for a Rec.709 transform does not only include a color transformation but also scales the signal from a full range signal into a legal range signal.
What Does All of This Mean for Working With Livegrade?
Based on the facts above, let’s look at the consequences when working with Livegrade.
Here’s the two most important facts in a nutshell:
- Use SDI output “3/4” when working with Livegrade, because when setting up a “Slog3” signal via “Look” the Exposure Index is applied, and this is necessary for consistent results later when working with the recorded clips.
- As the LUTs Sony provides to convert from a log to Rec.709, not only contain the log to Rec.709 conversion but also include a scaling from a full to a legal signal range, Livegrade requires to be set to a “Full In – Legal Out” configuration for consistent image results.
For example when working with FSI BoxIO you have to set it up so Livegrade controls the signal range, and then set the device in the Device Manager to a “Full In – Legal Out” setting.
Direct Rec.709 outputs from the Sony Venice however are in legal range, so as a rule of thumb we can say: Logarithmically encoded signals out of the Sony Venice are always encoded in a full range signal, Rec.709 signals are always encoded in a legal range signal. This also holds true for recorded clips.