4K Footage, Artbeats and You – Part 2
December 3, 2013 Leave a Comment
7 Examples of ways Artbeats maximizes 4K and Raw in our production workflow.
4K capture brings huge advantages to post-production. Production designers will use these advantages in different ways, depending on the application and finish. For stock footage production, we have our own specialized methods for exploiting all that resolution and color depth. In Part 2 of our series on 4K, I will share seven different ways we treat 4K and 5K footage in post to maximize quality and usability in our end product. These tips and tricks may give you some ideas on how to process your own 4K footage.
First, I need to explain that Artbeats offers two varieties of 4K footage, Raw and Color Corrected. The Raw version is for those that want to do their own color treatment and the Color Corrected is our own best attempt at being true to the original scene, giving moderate saturation and contrast without crushing blacks or clipping highlights. We also improve, or adjust, other aspects of the footage as needed. (What I am sharing below are just some of the things we do in our post-production workflow for the Color Corrected version.)
1. Cropping for composition.
The nature of our shooting is often “in the moment” as things are happening. We do not always have time to frame our shots perfectly. The 4K image gives us room to adjust the position easily while still fitting in a UHD (Ultra HD) frame size of 3880×2160.
Below is an illustration of how much room we have to crop while still maintaining 4K or UHD frame size:
When we shoot aerials, we have found that some gyrostabilization gimbals do not always get the horizon level. We can do almost 2° of horizon correction while still staying within the 4K or UHD frame. Here is an example showing the rotation fix and the 4K image: (surrounding image darkened to emphasize final crop)
Here is another example showing a crop to compensate for a lens distortion fix:
2. Adjusting Stabilization.
This is similar to #1 in that we are using the extra size of the image to give us room to apply a fix. In this case we are adjusting for undesirable wobble or shakiness, and also rotation since the horizon didn’t stay level. Once we stabilize the clip it usually still wanders outside the UHD crop, so we apply Bezier position fixes that “smooth out” the worst part of the instability while allowing some of the natural camera motion, thus keeping the image within the UHD frame size. This clip shows a side-by-side example of the kind of stabilization fixes that are common for us:
3. Cropping for driving plate format.
Our 5-Angle driving plates use a wider format than is typical. Since the top and bottom of the image is rarely used for these kinds of plates, we use a very wide-angle lens and crop to 3840×1200:
4. Matching frames and adjusting parallax for perfect HD 3D.
Even identical lenses won’t yield images that perfectly match. We found that we needed to adjust rotation, scale, position and then apply a mesh warp to compensate for lens distortion in order to match the left with the right. Then, proper parallax can be adjusted by moving one side horizontally. With 4K we can do all this and keep a clean image within a UHD frame.
5. Adding camera moves.
Sometimes a static shot needs a little movement to add interest. We can add subtle pan, tilt and zooms while still holding resolution in the UHD frame.
6. Adjusting mattes for compositing.
In the following example, we filmed tree shadows blowing in the wind. We used white foam core for the surface to capture the shadow. Unfortunately, it wasn’t practical to position the camera directly above the surface, so we shot it “off angle” as seen below:
Then in post we used Corner Pin to distort the foam core back to a rectangular shape and optimized to fit in a UHD frame size. Next, we removed color to give maximum contrast for the matte. Because we shot these images in 5K, the distortion didn’t soften the image excessively:
Then we used the matte on a background texture to indicate light and shadow as if streaming through a window:
7. Using Raw color depth to apply HDR (high dynamic range).
The problem with high contrast images is that detail and color are lost in highlights and shadows. Granted, the camera may have enough dynamic range to preserve detail in those areas; however, color saturation is lost the closer you get to the lightest highlights and the darkest of shadows. Adding saturation to the image doesn’t really help since it brings chroma higher in the mids keeping the chroma of the whole image still out of balance.
However, we have found that a 4K raw image set to a higher ISO preserves more chroma and detail in the shadows, while a lower ISO setting preserves more chroma in the highlights. In the case below, we imported the same Raw 4K file twice into After Effects, and set one ISO at 800 and the other at 500:
Then we took the brighter version and made a grayscale matte using a desatured version of the image. We added contrast to clip the highlights and crush the shadows slightly. Here we show the matte, the 800 ISO and the 500 ISO image:
By combining these images using the matte, we get the HDR result. Below, we show a “before and after” example of what the HDR treatment does. Notice the richer color in the sky and water:
In the case below, we used the blue channel to create the mask because the goal was to darken the sky:
Here is another example of a problematic high contrast shot showing the shot with and without HDR treatment. Notice that the detail and color in the lumber highlights is preserved in the HDR version. Notice the richer color of the grass. (This example is without any saturation added.)
We hope you have enjoyed this little tour of how we make the most of our 4K and 5K footage in post, and perhaps it can inspire you to experiment as well.