Drone HDR – How to Easily Improve Your Low-Light Photographs

  • Shoalhaven Heads

Drones have revolutionised photography and film-making. These days there aren’t many serious photographers who don’t have a Mavic Pro in the old kit bag next to their DSLR and who don’t think twice about getting an aerial perspective on familiar vistas. The photos that are possible with drones such as the Mavic can be incredible, but there is one area of photography where they do not excel and that is in low light.

The problem is that, unless you’re flying a professional machine with a DSLR strapped underneath it, the modern drone does not have a very good sensor. For the most part, the sensors are small and exhibit heavy noise artifacts at anything above baseline ISO levels. You only start getting decent quality from drone/lens combinations once you head into DJI Zenmuse territory. Yes, drones are excellent during the day – great colour rendition and clarity – but in low light, at sunrise or sunset or heavy cloud, they suck.

There is however, a way of getting decent quality images from a consumer drone in low-light. You need to be a little bit organised and there is some post-processing involved afterwards, but it’s not technically difficult. Here’s the process.

Choose the right conditions

Low light photography works best in drones in still air or very light winds. As soon as the drone has to start compensating for wind, it will be in constant motion and picture quality will degrade slightly as a result. Since we will be combining images later any movement between frames also results in reduced image dimensions. So having the drone as stable as possible is important. Perfect conditions are quite rare of course and all of these techniques still work perfectly well when there is wind.

Shoot Bracketed Shots

The key to getting the best possible low light photographs with a drone is to shoot bracketed shots in RAW mode. Bracketed shots are a sequence of photos taken at a variety of exposure levels in order to capture as much of the dynamic light in the scene as possible and RAW images contain the unmodified sensor information that enables you to get the most possible information from each capture as possible. Typically bracketed shots are taken in sequences of three or five depending upon the circumstances. I would advise you to shoot in sequences of five because the end result will have a more subtle transition between the dark and light areas of the image.

The good news is that the ability to take bracketed shots is built into all the popular drone apps. In both the DJI and Litchi apps, it can be found in the photo settings section under the heading AEB. Simply select the five shot AEB option and when you press the shutter button on your remote or app the drone will quickly take five photographs at a variety of exposures instead of just one. If I am shooting towards the sun then I often take two sets of five AEB shots, one with automatic exposure and then one with the exposure meter centred on the sun.

If the conditions are good and wind levels are low then it’s entirely possible (and sometimes more desirable) to manually bracket your shots using the apps histogram. To do this you simply need to set an exposure that correctly exposes the shadows in the image and then work your way through the dynamic range to ensure that you have frames in which neither the highlights or the shadows are clipped and in which you have a full range of image data in the mid-tones as indicated by a histogram with a smooth ‘hill’ shape.

If you have a fairly slow SD card in your drone then remember to give it time to take all of the images before you move its location or gimbal angle. Wait until the progress indicator has finished rotating on the shutter button before moving.

Tone-Map Your Images

Once you’ve imported your photographs from the SD card onto your computer you can begin processing them. There are many options for combining bracketed images and I’ve tried pretty much every single one of them over the years, but for drone shots I feel that the best look is achieved by using HDR blending using one of Adobe’s applications. In many cases the HDR blending in Lightroom is all you will need and you can achieve superior results using it. However you may want more flexibility and in that case the HDR blending in Photoshop is a good choice.

Here is an example of an image I took with two sets of five images shot in AEB mode. If I had left the drone to meter automatically then the highlights would have been blown out (as per the lower set of five) so I manually set exposure for the setting sun to ensure I captured the full light range (as per the upper set of five).

To blend your images to HDR in Lightroom, simply select all the exposures and either select Photo > Photo Merge > HDR or press Command or Ctrl+H. When the preview window appears I always deselect the ghosting option and auto-tone but I do leave auto-align enabled. Click the Merge button to begin the HDR rendering process.

If you’re using Photoshop’s HDR option, then you should first select your exposures, right-click and then Edit In > Merge to HDR Pro in Photoshop. Ensure that the HDR Pro window has 32-bit selected and click the Tone in Adobe Camera Raw button at the bottom of the screen. You can now post-process the image to your own personal tastes using the 32-bit image file which will generate a much more subtly processed image than the straight 16-bit HDR in Lightroom.

Remember when you are processing the image in Adobe Camera Raw that you have far more latitude with the sliders than you would with a single RAW image. For example, you can alter the overall exposure of the image to a far greater degree than you can with a single image but still retain full control over the shadows and the highlights using the global sliders or individual modifications using the brush, radial or graduated filters.

 

For a full walk-through of the whole process including the settings to use in your drone app, please check out my tutorial video below:

By |2018-07-02T12:47:56+00:00July 2nd, 2018|Articles, Techniques|2 Comments

2 Comments

  1. Phil July 2, 2018 at 3:09 pm - Reply

    Great write up, Andy. Can I please ask, what type of drone do you use? I’m considering getting a DJI Mavic Pro later in the year, but I also like the Phantom 4, which seems to be a better option for shooting. Any advice would be appreciated? Thanks.

    • Andy Hutchinson July 2, 2018 at 3:56 pm - Reply

      Thanks Phil. I have a standard Phantom 4 (not advanced or pro). The more recent Phantoms (particularly the Pro) have better sensors than the smaller drones and consequently better images – they’re also more stable in flight. The question you need to ask yourself is where and how you intend to fly your drone. If you intend to walk into the bush to film scenery that is off the beaten track the you should definitely get one of the more portable drones such as the Mavic Pro. However if you are only ever going to drive somewhere and fly the drone within close proximity to where you parked then get the P4. 🙂

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