One of the challenges of shooting video with a drone is dealing with high dynamic range lighting situations. Fortunately, many of DJI's drones offer a useful picture profile called D-Log.
It's DJI's implementation of a Log gamma curve, designed to capture as much tonal information as possible.
DJI's standard picture profiles can be vivid and punchy, but similar to shooting JPEG format on a stills camera, using them can make it impossible to recover highlights or shadows if clipping occurs in high contrast scenes.
If you don't need to shoot Log to capture the dynamic range of a scene, it may not be
the best choice
Using D-Log can give you more flexibility in your post-production by retaining a wider tonal range, allowing you more latitude to apply your color and style choices during editing. However, there's no such thing as a free lunch; shooting in Log can reduce image quality by trying to compress too much tonal information into a limited number of bits in the file. If you're shooting a high dynamic range scene that tradeoff may result in a net benefit. But if you don't need to shoot Log to capture the dynamic range of a scene, it may not be the best choice.
In this article, I'll show you how to set up the D-Log profile, how to expose for it, and provide some examples of what you can achieve by shooting in D-Log and using color lookup tables, or LUTS, to color grade the final footage.
Set up your DJI drone to shoot in D-Log
To set your Mavic Pro, Phantom, or Inspire to shoot in D-Log, make sure you're in video mode and navigate to your camera settings. You'll find D-Log under the 'Color' settings, along with all the other color profiles. Once selected, you're ready to shoot in D-Log.
To set up D-Log using the DJI GO app, simply navigate to the Color settings in video mode and select the D-Log profile. I also recommend going to the Style settings and creating a custom style with sharpness, contrast, and saturation set to -3 to give yourself more flexibility in editing.
I also recommend going to the 'Style' settings and creating a custom style with contrast, sharpness, and saturation all dialed back to -3. This can give you a bit more flexibility in post-processing since you're not baking things such as the default sharpness level into the file.
Your drone should now be set up and ready to record footage in the D-Log profile. Keep in mind that the image above is from the DJI GO 4 app using the Phantom 4 Pro; menus may look slightly different on different models, but it should be the same basic procedure.
Setting exposure in D-Log
Now that your drone is set to shoot in D-Log, let's discuss some best practices and tips for properly exposing your footage. We'll be using my screenshot below to point out some key settings.
When shooting D-Log, I've had good experience using the expose to the right (ETTR) technique in order to get more shadow detail while preserving highlights.
There are different schools of thought on how to best expose when shooting in Log, but I'll share what has worked consistently for me.
In the image above, note that my histogram is exposed as far to the right side of the scale as possible without clipping my highlights. This is a technique called expose to the right, or ETTR. Exposing this way for D-Log allows for less noise in the shadows while maintaining highlights as much as possible. For the way I shoot, it's the 'sweet spot' for maximum dynamic range retention.
Alternatively, you can optimize exposure for the mid-tones when shooting in D-Log. However, note that D-Log footage can get very noisy if underexposed. If exposing for the mid-tones means using a lower exposure than the ETTR method, it will result in more noise in the shadows in exchange for better highlight retention in the brighter regions of your image. I suggest trying both methods to see what works best for you.
The other key thing to note about my settings is the fact that ISO is set to 500. It's the lowest ISO that DJI D-Log can be shot in on the current Phantom 4 Pro firmware. That means you can go higher than ISO 500 if you'd like, but never below ISO 500. I recommend leaving your ISO at 500 to get the best results.
Using LUTs to color grade D-Log footage
Recording your footage in D-Log offers many benefits, but one of the things that you have to do in order to reap those benefits is to devote more time to post-processing. Straight out of the camera, Log footage looks very flat since it's designed to cram as many tonal values into the available space as possible.
The first step in grading your D-Log footage will be to make it look like something more recognizable. To do this we'll use a LUT, or lookup table, to apply a different gamma curve (tone curve) to our footage using our video editing software.
A LUT is essentially a matrix of numerical data that describes how to modify our footage from the profile it was shot in, to a profile we want to work with.
All of this work with LUTs typically takes place in your video editing software. I use DaVinci Resolve, but the same basic process can be performed in other editors like Final Cut Pro X or Premiere Pro. Once your footage has been imported, you can apply a D-Log to Rec. 709 LUT, which converts our D-Log footage to the standard color and tone response for HD video. At this point, our footage should more closely conform to the standard color output we're used to seeing.
Having the flexibility to push and pull colors and exposure in editing is worth
the added effort for me
DJI used to provide a LUT for this conversion but has stopped offering it since the Phantom 4. I like to use Blackmagic's DaVinci Resolve because it has a D-Log to Rec. 709 LUT built in, but other third-party plugins like Filmconvert also offer them with their color grading tools as well.
From here it's possible to finish color grading manually if you wish. Alternatively, you can use another LUT to apply a new 'look' to your Rec. 709 footage, such as one that emulates a film stock or provides a specific cinematic look, to achieve the output you're going for.
When editing in DaVinci Resolve it's easy to apply a D-Log to Rec. 709 LUT to convert my footage. The general workflow is similar in programs like Final Cut Pro X or Premiere Pro, though you may have to add a D-Log to Rec. 709 LUT to your software.
One of my workflows is to use the 'D-Log to Rec. 709' LUT in DaVinci Resolve, followed by a cinematic LUT from the Elektra series from Polar Pro.
To be clear, Elektra LUTs are intended to convert your D-Log footage directly to a cinematic look, and they absolutely work in that respect. However, after some experimentation I've found the results can sometimes be more pleasing – to me, at least – when I apply these LUTs to footage after applying a D-Log to Rec. 709 LUT. Both methods work, and it's really a matter of personal taste and the look you want to achieve.
There are other sources of LUTs designed for DJI drones as well, including collections from Ground Control, and even D-Log LUTs created by the user community (just do a bit of searching online).
I like to go through my library of available LUTs and try them until I find the one that suits the project. I've put together a short sample reel of some D-Log footage from a flight at Seattle's Gasworks Park, so take a peek at the video for some examples of different looks.
This video shows a number of looks I was able to create from the same shoot using different LUTs.
Keep in mind that LUTs don't eliminate the need to do manual color grading; they're a starting point that allows you to apply a consistent look across your footage, but you'll likely still need to do a bit more work to get the precise result you seek.
Conclusion
Now that you know how to set up your DJI drone to shoot in D-Log, expose it for maximum dynamic range, and color grade it using LUTs, you're ready to create your own cinematic aerial films. I've found that the additional workflow required to shoot in D-Log has given me enough benefit in post-production to continue using it. Having the flexibility to push and pull colors and exposure in editing is worth the added effort for me.
Granted, I probably wouldn't employ this process for casual shooting, but for important productions where use of a high contrast color profile would risk clipping a lot of highlights or crushing shadows straight out of the camera , shooting in D-Log is definitely a must. DJI has even created a handy guide to getting started with setting up and shooting in D-Log as well, so if you'd like more information on the process, take a look at that guide here.
. dpreview.com2018-2-9 17:00