AJA FS-HDR for DPs and DITs

Bryce Button, AJA’s Director of Product Marketing, explains the FS-HDR and how it helps in cinema production. 

JON FAUER: What can the AJA FS-HDR do for motion picture production? 

BRYCE BUTTON: When it comes to cinema production, there are a number of demands that suggest the ability to correctly monitor HDR on set or location would be of great benefit for production teams. About two years ago, there was discussion at an event at the Dolby Theatre in London about Netflix productions using HDR for much of their delivery. In talking to production teams, we heard that they were struggling a bit on-set. One reason was that they couldn’t view HDR with the standard monitoring systems they had. And, they couldn’t clearly see how much detail was actually coming out in the background of scenes as they were working with SDR displays. 

In HDR, everything feels more defined because of the deeper color space and the extended dynamic range. Without a clear idea of how the background components competed with the foreground focus, they felt that they would have benefited from rebalancing light sources and potentially recomposing shots to maintain the dramatic intent and the viewer’s interest. Post companies, of course, were happy. It meant that when post-production began, they had to do a lot of work to adjust. 

The second challenge was that a lot of detail that might have gone unnoticed before—especially around make-up and set design—was now clearly visible. So, they had to factor in a number of aspects on the shoot: especially composition, lighting and make-up. The question they had at that point was the need for a better way to monitor on-set. They said, “We can’t quite tell, with our standard SDR feed, how much is going to be affected by the time we get into the post process. And we may actually want to alter our lighting set-ups, and so on, to compensate.”

So that was an initial need we saw when it came to production. We talked about it internally at AJA and how to address these challenges. Right from the beginning with the FS-HDR, we had the ability to take a straight 4K signal off a single camera. But FS-HDR also supports four-channel mode and you can run four HD signals which could help with matching cameras. In either case, you can run transformations that either show you SDR or HDR. 

How can the AJA FS-HDR help Cinematographers and DITs?

Cinematographers were intrigued for a number of reasons: they could get a better representation of how their work would look in HDR early on. And, with multiple camera setups, they could view up to four camera feeds on a 4K/UHD display with HDR while also down-converting to HD with SDR on another for comparison.

In our conversations with cinematographers prior to launching FS-HDR, a number of them didn’t feel they were getting an accurate representation of lighting, look and color straight off the camera. One of these cinematographers is Claudio Miranda, ASC. He desired a feed and a signal that would give him a bit more of an accurate display of what he was trying to achieve aesthetically, which made the FS-HDR appealing on two fronts. 

Above all, the Colorfront Engine, which is the standard FS-HDR operational mode used for color transformations, is highly pertinent for digital cinema because it benefits from the years of work Colorfront has spent on digital cinema productions. By the way, Colorfront transformations are also valid for broadcast and offer parameter controls for that purpose. 

FS-HDR additionally offers BBC HLG LUT transformations to meet broadcast needs if that is your final destination for your project. (A BBC description: “High Dynamic Range…means water can glisten, stars can twinkle, and sunlight can be golden, all whilst maintaining detail in the shadows. Hybrid Log-Gamma (HLG) is an HDR system that was specifically developed for television by the BBC and Japanese broadcaster NHK.”)



(center) Ethernet and Fiber Inputs and Outputs (middle right) SDI BNC Connectors Inputs and Outputs (far right) SDI and HDMI to Monitor

For cinema, however, Claudio was very impressed by the fact that the Colorfront Engine transformations aren’t just simply mathematical but rendered as a true representation of the desired aesthetic. Intrigued, he said, “OK, but on-set we don’t always need to show 4K for monitoring. It would be wonderful if I could see multiple cameras, especially when trying to match their looks.” 

So here we have lower resolution HD-HDR transformations. And, FS-HDR will indeed do that. In terms of getting the feeds from the camera into the box itself, if you’re going to bring four separate cameras together, another concern is cabling. Cameras may be great distances apart, so the fact that the FS-HDR also supports SFP cages for fiber was appealing for his needs. It supports very long cable runs from each camera to the unit, including from cranes and remote heads. All four incoming camera signals can be adjusted separately as needed. In other words, you can set separate transformations or tweak parameters when the demand arises. 

To be clear, with the Colorfront Engine, you might choose the same preset transformations, and all is well. Let’s say you’re transforming to PQ (Perceptual Quantizer system developed by Dolby). But you also want to slightly adjust luminance or color settings, as the cameras might be from different manufacturers or their physical on-set location might dictate slight tweaks due to lighting and so on. 

FS-HDR offers those abilities. Coming out the back of the box, you can go into a single monitor that accepts four 3G-SDI inputs (e.g. SONY BVM-X300). Or, with 12G-SDI becoming more prevalent, you could use a 12G-SDI monitor. Either way, you’re effectively able to look at all four HD signals with HDR color transformations applied.

The advantage is that it becomes much, much quicker for the Cinematographer, the DIT and the Director to quickly decide how to make things match better and to deal with any background issues in frame that HDR makes apparent. FS-HDR provides a very pragmatic approach that ultimately saves time in post and helps prevent costly post fixes down the line because the on-set images more closely mirror the final look they’re trying to achieve.

Talking about the camera inputs, the FS-HDR is extremely flexible in that it allows you to bring in Log formats from many different cameras for real time transformation. It’s not uncommon to be working with a range of cameras on-set: RED, Sony, ARRI, Canon, Panavision, Panasonic, etc. FS-HDR supports separate real-time conversions for each source, bringing them all into the PQ space, for instance. This makes it a lot easier and faster to spot issues that require immediate attention on-set. 

On a four camera set-up, how do you connect the HD-SDI outputs of each camera to FS-HDR inputs?

A straightforward run would include four 3G-SDI inputs, one from each camera. If taking the HD outputs from these cameras, they would be 3G-SDI. You could also choose to be coming in from 4K or UltraHD cameras as well, running at 12G or 6G-SDI. FS-HDR offers SFP+ connection cages (Small Form-Factor Pluggable) for either 12G-SDI coax (HD-BNC) or fiber inputs, which is excellent for some of the latest cameras to hit the market. 

Claudio, for instance, ordered the SFPs on his FS-HDR because he wanted to use fiber, and this gives him a couple of choices. He could go 12G-SDI off a single Sony VENICE camera doing 4K. Or he could be using four 3G-SDI fiber connections for long runs from multiple camera inputs.

And the monitor output is SDI?

One of our latest firmware upgrades allows you to monitor over HDMI with HDR metadata and 4K-SDI, or up to 4 signals of HD-SDI and HDMI. This allows you to do simultaneous outputs. You could use the four 3G-SDI outputs or even the fiber outputs from their SFP ports and simultaneously send an SDR version to a standard HD monitor. That way, you can see how your production might look in both HDR and SDR. This approach has been extremely popular with broadcasters, but is also a good application for cine production because it gives you a great view of how your HDR production will look on a standard set as well.

Just to play devil’s advocate, let’s assume that we have the latest HDR OLED monitor on set. Would we still use the FS-HDR?

Absolutely, because you’ll use the FS-HDR outputs to drive the monitor. The key reason you might not just go straight into the monitor is that the monitor is not necessarily capable of doing all the transformations from the various Log formats. So, the key function of the FS-HDR in this instance is compiling those various camera inputs and transforming them for HDR viewing. 

On top of that, Colorfront has made great strides with their transformation work, focusing on the retention of artistic intent, and not just a straight mathematical transformation. We heard this throughout early testing with beta sites for instance. They believed that even feeding the best cameras into the best HDR monitors, our transformations from S-Log to HLG or PQ look better than what the cameras and monitors might be doing themselves, because of the FS-HDR’s retention of artistic intent.

I have also heard this from a number of Cinematographers and Colorists whom I respect. They say that the FS-HDR provides images that are more pleasing to the eye than they get with a straightforward camera to monitor setup.

With the FS-HDR, can you tweak how the image looks?

Yes, you can tweak through various parameters. But even straightforward “select and forget” built-in Colorfront transformations certainly look better.

What adjustments are available?

There are 21 parameters for making adjustments. (see the FS-HDR manual: aja.com/products/fs-hdr). You can affect dynamic range, gamma, HDR amount (color volume expansion), etc. This is all done within the Colorfront Engine, either by FS-HDR’s built-in web browser GUI or using the free FS-HDR Control Link software to plug in a Tangent Kb panel, which can be quicker because it’s a dynamic, physical, tactile device.

There’s also Master Lift, Gamma, and Gain—both universal and by color—all the basic color controls. The Exposure control is interesting. It’s an equivalent to adjusting the amount of photons landing on the camera sensor.

At IBC, we will introduce version 2.6 firmware. It includes a few updates that will appeal to DPs and DITs. We’re going to add a new S-Log 3/BT.2020 output, which basically extends the support for S-Log coming from the Sony side, and ARRI Log C output for ARRI. They are especially interested in this for working with multiple AMIRAs to get consistency from the various cameras into the switchers before finally going HLG for HDR output. That’s a pretty big request from ARRI Rental and others.

We’ve also expanded our BBC HLG LUT support, which is important for certain broadcasters. In sports productions over the summer, broadcasters found that SDR could become overly saturated in the some competing HLG processes. The new LUTs from the BBC assist in consistent round-tripping between HDR and SDR as materials rotate round from one to the other.

Additionally, the new firmware update integrates PQ4000 to HLG conversion, which speaks to the industry’s embrace of HDR. With HDR now taking off, high-end high Nit-level counts are coming into play, and a lot of settings for digital cinema production in particular have been mastered for PQ4000. This is going to allow a recognized transfer of PQ materials at 4000 Nits to HLG when you get the finished cinema product going out on television.

Another exciting development is the addition of custom LUT uploads, including 3D LUTs in 33 point .cube formats, which will be an incredible benefit on-set. Some productions like to set a LUT because they have a particular look in mind. They’ll be able to upload it and see how it will look on-set and in a final view for PQ, HLG and SDR, as needed.

Finally, we’re also rolling out gang operations. FS-HDR Control Link software will link a Tangent 12-knob Kb panel to an FS-HDR for control of the Colorfront Engine, so that you can gang-control multiple FS-HDRs in the same network. 

Why is this important? It enables real-time 8K workflows. It lets you set parameters for multiple FS-HDR units attached to different sources simultaneously. For example, you’ll be able to gang four FS-HDRs together for 8K (4x 4K) and use a single parameter control to adjust any or all of those ganged units at the same time. This will be of interest to NHK and others on the leading edge of 8K.

Would you be able to do a 4K quad split?

Yes, you’re coming out of four FS-HDR units and you could drive them to four 12G-SDIs going into a single display.

What flavor of HDR is coming out of the FS-HDR?

On the output side, you have a number of options. We’re supporting PQ, which is the same thing as HDR10 for HDMI. HDR10 is just a designation in terms of HDMI output. You can output to SDR Rec.709 at 100 Nits, which is normal television. You can do PQ BT.2020 at 1,000 Nits. You can do HLG BT.2100 and also output with Sony S-Log S-Gamma3. And then two new ones that will be coming. So that’s six different types of HDR output.

So the FS-HDR is an essential box to have on set if you’re working with HDR, no matter what.

Yes, we think so. We’re seeing a lot of excitement from cinematographers because they trust the transformations and like the flexibility of connectivity options—3G, 6G, 12G-SDI—over coax or fiber. Cinematographers and DITs like the ability to tweak them as needed either with the front panel, a hardware control panel, or the web-browser UI. Supporting LUT uploads in v2.6 will likely be yet another addition to FS-HDR’s continued popularity on set and on location.

Reprinted from Film and Digital Times September 2018 Edition #89-90

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