Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
|

Achieving Ultimate Image Quality with the DJI Air 2S

TL;DR: Always use 5-exposure AEB in manual mode at ISO 100. Never use SmartPhoto.

The DJI Air 2S has replaced my original Mavic Pro as my flying camera, AKA drone. I used the Mavic Pro for almost six years since January 2017. At that time, DJI’s portable folding quadcopter was revolutionary and opened the door to aerial photography and videography to a huge new audience who, like me, thought that aerial photography was cool but had no interest in lugging around something like a Phantom drone. Five years later, DJI released the Air 2S as an “all-in-one” drone for serious photographers, and many reviewers have marked it as the successor to the OG Mavic Pro as DJI has taken the Mavic name up the price scale with the Mavic 3 Pro starting at $2,200 and going up to $5,000! I decided it was time for an upgrade and was able to pick up an almost new Air 2S Fly More Combo from the used department at B&H Adorama for $1059 (and managed to sell the Mavic Pro for $450).

DJI Mavic Pro

With the introduction of the Mavic Pro in late 2016, DJI also introduced a slew of not-so-well-documented features, and the early adopters spent a lot of time figuring out how to best use the incredible imaging tools that the wizards at DJI had made available to us. However, the small 1/2.3″ camera on the Mavic Pro did have some severe limitations, and multiple exposures were needed even for shots captures in the middle of the day to reduce noise (see the blue sky comparison down below). I did some testing within the first couple of weeks of having the Mavic Pro and determined that the best results were produced by capturing a 5-shot set of exposures using AEB in manual mode. A few months later, I discovered that even better results could be achieved using the in-camera HDR DNG mode. In HDR mode the Mavic Pro took quite a bit longer to capture a photo, and I don’t know exactly what the Mavic Pro was doing, but the result was a beautifully detailed image with absolutely no noise! The image quality was better than what I could achieve combining multiple single exposures using HDR in Lightroom. I used this mode exclusively for every photo captured with the drone afterwards.

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photographyAchieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
Mavic Pro Image Quality Comparison
Single Exposure (left)/4-shot HDR (right)

Air 2S Camera Sensor

From my perspective, the most compelling upgrade of the Air 2S over the OG Mavic Pro is the move from a 1/2.3″ 12MP sensor to a 1″ 20MP sensor, along with the accompanying leap in video bitrate from 60Mbps to 150 Mbps and the gimbal build quality (the Mavic Pro’s gimbal was literally attached with rubber bands!). The camera in the Air 2S is built around some version* of the 1″ Sony Exmor R sensor, likely the IMX283 used in the Mavic 2 Pro and Phantom 4 Pro as well as in the highly praised Sony RX100 (Mark II and III, later versions have the Exmor RS/IMX383 sensor) series of compact cameras. The sensor is likely the same as the 1″ sensor found in the Mavic 2 Pro and Phantom 4 Pro, although it is possibly a later variant that supports faster readout for video since the Air 2S captures 5.4K up to 30fps and 4K up to 60 fps whereas the Mavic 2 Pro is only capable of 4K up to 30fps. Or it could be the newer “stacked” Exmor RS (IMX383) sensor. There’s no difference in image quality between the IMX283 and IMX383; the stacked design of the IMX383 allows for faster on-chip electronics that make things like eye-detect auto-focus with continuous subject tracking at 30 fps possible.

For such a compelling list of specs, there is surprisingly little useful information available regarding the true capabilities of this camera, either for the Mavic 2 Pro or the Air 2S. Aside from the different video capabilities, the other differences are the focal length (28 mm for the M2P, 22 mm for the Air 2S), variable aperture on the M2P, and the inclusion of the Hasselblad Natural Colour Solution on the M2P. Most of the reviews either focus on video or simply repeat DJI’s own marketing jargon.

Exmor R Sensor Capabilities

The plot of photographic dynamic ranges shows that the PDR for the back-illuminated Exmor R sensor is 8.8 at base ISO and compares roughly to ISO 500 for Sony APS-C (a6400) and ISO 1000 for Sony full frame (a7IV). I shoot at ISO 400 on my Sony a6500 quite a lot since it is the second base ISO for that camera, so this comparison make sense to me and I can see a lot of similarities in image quality between the cameras at these settings. The smaller 1″ sensor is also losing about 1.5 stops of dynamic range from current APS-C sensors and 2.5 stops from the latest full frame sensors.

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
Sony Exmor R (RX100 Mark III) Image Sensor Dynamic Range Compared to a6400 and a7IV

The second chart of shadow improvement versus ISO suggests that there is no improvement in shadow detail with increasing ISO above 100 for photographic still images with this sensor (the sensor is relatively ISO invariant but does not have the dual gain ISO found on the larger Sony sensors). The flat curve indicates that no additional shadow details is gained by raising the ISO in-camera, so the same benefits can be realized by increasing exposure in post. However, these results are derived from images taken with a Sony camera and are not directly applicable to the Air 2S. My testing shows that ISO 100 images can be pushed about 3 stops (equivalent to ISO 800) and provide equal or better image quality. Beyond 3 stops, it’s probably better to raise the ISO but this really depends on the particular situation and if you need to retain highlight detail in the image.

https://www.photonstophotos.net/Charts/PDR.htm#Sony%20DSC-RX100M3,Sony%20ILCE-6400,Sony%20ILCE-7M4

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
Sony Exmor R Shadow Noise. The values do not increase with increasing ISO, so there’s no benefit to shooting stills with ISO above 100.

https://www.photonstophotos.net/Charts/PDR_Shadow.htm#Sony%20DSC-RX100M3,Sony%20ILCE-6300

Air 2S SmartPhoto

SmartPhoto combines scene recognition, Hyperlight, and HDR imaging into one intelligent algorithm that produces sharp images with minimal effort.
Scene recognition optimizes different camera parameters for various scenes and supports intelligent recognition of five categories: sunset, skies, grass, snow, and trees.
Hyperlight optimizes photos taken in low-light conditions, resulting in less noise and enhanced clarity.

DJI.com

On the Mavic Pro using the DJI Go 4 app, I captured photos exclusively using the in-camera HDR DNG mode. It was this capability that allowed for much better image quality under high dynamic range conditions than expected for the Mavic Pro’s tiny 1/2.3” sensor, and I found that it produced images with equal or better quality than single bracketed exposures merged in Lightroom. I typically would set -0.3 to -1 EV exposure compensation in HDR mode or else capture a couple of manually bracketed exposures in HDR mode for later blending. The image below shows a comparison (at 200%) of the excellent image quality produced by the in-camera HDR processing compared to the noise typically seen in a single exposure from this camera. I didn’t observe any loss of detail in the HDR DNG on the left but the image shows zero noise in the blue sky. This is a dramatic improvement over the single exposure image on the right where the sky is very grainy.

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
Mavic Pro Image Comparison: In-camera HDR DNG (left)/Single Photo (right)

At first glance, SmartPhoto seems to be the current replacement (available in the DJI Fly app) for the in-camera HDR DNG option available in the DJI Go 4 app. However, SmartPhoto does not provide any user options, such as the ability to specify an exposure compensation value, so we have no control over how the photo is captured in this mode. To make matters worse, setting the camera to SmartPhoto mode does not even guarantee that the camera will capture an HDR image. As I was reviewing images for this post, I realized that although I had used the SmartPhoto mode for several images, none of them were captured as HDR images (they were all captured as single photos by the camera). It seems that the “intelligent algorithm” used to determine when HDR is needed could do with some extra IQ points. Although the dynamic range of a scene may not strictly dictate that HDR is necessary, there are tangible benefits to image quality that this approach neglects.

In the image below, SmartPhoto only captured a single exposure. To be fair, the highlights in the clouds are just clipped in the red and green channels, and the extreme shadows at the bottom of the photo still show details when brightened. So technically, maybe this is scene does not require HDR. However, when zoomed in, there is noise apparent all over the image and especially in the dark blue sky on the left side. An HDR exposure would all but eliminate this noise.

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
SmartPhoto example with almost blown highlights. The Intelligent Algorithm exposed this scene as a single photo rather than using HDR.

Unfortunately, without the ability to manually control the exposure, DJI has severely limited the usefulness of the SmartPhoto mode. Essentially, if I am capturing a scene with challenging lighting conditions, using SmartPhoto is a complete gamble, and I cannot trust it to properly expose the image without blowing out the highlights. If I’m capturing an epic scene from 250 feet above the ground, I don’t want to risk getting a ruined image by trusting SmartPhoto to be intelligent enough to properly expose the scene. For casual JPG shooters it might be useful, but for professionals SmartPhoto is useless (actually, it is complete junk). The example below illustrates this point.

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photographyAchieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
Another example of SmartPhoto being dumb-the Air 2S captured this scene as a single exposure photo. The highlights in the bright area on the left of the image are completely blown while the shadows in the foreground are very dark.

Air 2S AEB Bracketing with DJI Fly

For the Air 2S, the DJI Fly app provides an option to capture 3 or 5 bracketed exposures with 2/3 EV change between exposures (and no option to change that exposure difference). Unlike SmartPhoto, we do get the option to set the exposure compensation with AEB, or the user can touch the screen to bias the exposure on the selected region of the scene. In manual mode with ISO set by the user (to 100 of course), the camera adjusts the shutter speed to change the exposure. Although the individual exposures have to be merged later, AEB provides the most control and flexibility to ensure optimal image quality at the expense of using up 5-times the storage for each photo captured and having to manage all the extra photos in the image catalog.

Air 2S HDR
Lightroom HDR from 5-shot AEB

Air 2S Photography Recommendations

When In the Air

SmartPhoto can give good, but not optimal, results. There is a strong possibility of blown highlights and no guarantee that the camera won’t just take a single photo, and, if it does, then the image produced is not as clean as an HDR merged from multiple exposures.

My recommendation is to always use the 5-exposure AEB option (if multiple exposures are needed, why stop at 3?) in manual mode at ISO 100. If there are strong highlights in the scene, underexpose by ~1 EV. Keep in mind that the dynamic range of this sensor lags behind larger camera sensors, so bracketing is necessary to capture the scene without clipping and minimize noise.

Shoot at ISO 100 and increase ISO only when needed in low light to maintain a minimum shutter speed in windy conditions for extreme low light or nighttime conditions. Based on my informal testing, ISO 100 at +3 EV looks as good as ISO 800 at 0 EV. If raising the ISO, images at ISO 400 look great but I would not want to use anything higher than ISO 800. ISO 1600 can be usable with AEB. In extreme low light, using SmartPhoto to capture a HyperLight photo might be an option although I have not tested it yet in a real world scenario.

AEB Example

The image below shows a comparison of a single, properly exposed image and a 2-shot HDR composite of the same scene. The base exposure for this 5-shot AEB was set at -1 EV, and the darker exposure at -1.7 EV was needed to capture detail in the brightest area of the scene. Because of the extreme brightness and need to underexpose, the total exposure for the image had to be bumped to +2.46 EV in Lightroom with the Shadows at +74 for the final processed image. Boosting the exposure and shadows greatly enhances any noise in the image, so anything we can do to reduce noise will greatly increase the image quality.

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
Noise Comparison at 200%: Single Exposure at 1/730 second (-1.7 EV) on left; HDR Composite of 1/180 (+0.3 EV) and 1/730 (-1.7 EV) on right.

When Processing

If using Lightroom to merge the exposures to an HDR composite, use only the darker exposures necessary to capture highlight detail. In the example below, I used only 2 of the 5 AEB exposures to create the HDR. The darkest exposure (at 1/1,250 second) was not needed because all of the highlight detail was captured in the 1/730 second exposure. In addition, the darkest exposure was very noisy so it was not useful for improving the image quality.

Achieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photographyAchieving Ultimate Image Quality with the DJI Air 2S Air 2S, dji, drone, ETTR, HDR, ISO, iso invariance, lightroom, Mavic, photography
Left: Single Image, 1/730 sec (-1.7 EV) | Right: 2-shot HDR, 1/730 sec (-1.7 EV) and 1/180 sec (+0.3 EV)

Conclusion

Ensuring optimal image quality is a critical aspect of digital photography and should always be kept in mind when capturing images. To be fair, the photos featured in this post were captured under very challenging lighting conditions for any camera. When I examined some images captured by the Air 2S on a blue sky afternoon, I can hardly see a difference in the 100% crops between the single photo and an HDR composite. The camera on the Air 2S does provide impressive image quality and is a huge upgrade from the Mavic Pro.

But landscape photography is not often about taking photos in ideal lighting conditions. I captured these images on my first real outing with the DJI Air 2S. I hadn’t planned on doing any serious photography that evening, but the weather conditions dictated otherwise, and fortunately I was able to capture some epic images with my new flying camera. I posted a few of these photos to social media and the next day received a message that the owner of the ranch where we had been photographing wanted a print of the title image for this post. Fortunately, I had shot the AEB images in addition to the SmartPhotos and was able to use the HDR composite to produce a high resolution, high quality metal print of the photo (and earned back more than a tenth the cost of the drone on the first day).

At this point, the Air 2S has been out for 16 months, so I’m not optimistic that DJI will make a change either to the drone’s firmware or in the Fly app to give us back full control of the camera so that we have the ability to capture in-camera HDR DNG images when the photographer, not the camera, decides it is needed. It seems like SmartPhoto could be included as it is when the camera output is set to JPG, and when output is set to DNG, the app could provide HDR and HyperLight as separate options for use by more experienced photographers.

*I’m not an authority on this sensor; I’m only summarizing what I’ve been able to find online. Sony only produces one line of 1” sensors for consumer cameras (used in the RX100 line), the IMX283/IMX383, and I was able to confirm (from some sample code from a DJI SDK on github) that the Mavic 2 Pro carries the IMX283. The published specs for that sensor are consistent with the capabilities of the camera in the Air 2S, notably 5.4K at 30 fps and 4K at 60 fps, so I’m betting the Air 2S has the same sensor. I’ve found nothing definitive to indicate the newer IMX383 was used in the Air 2S. But I could be completely wrong.

Leave a Reply

Your email address will not be published.