DJI Inspire 1 X3 Camera Sweet Spot

washed out sailYou could just point and squirt, use the camera on auto and concentrate on pointing it in the right direction, but it’s hard enough to get the UAV in the right place, at the right time and with the subject framed just right without having to manually adjust the camera settings as you fly.

You’ve spent lots of money on your UAV so why not try to get the best out of it?  After receiving lots of advice and tinkering and playing and failing and trying again, he’s my process for squeezing the best video out of the X3.

Why not auto?

The auto settings on most cameras will either base the exposure settings on a single point or a matrix of points around the image.

washed out sailsSingle point auto-exposure is great if you can keep your subject directly in the middle of the frame and don’t care if the surrounding image is over or under exposed.  If you can keep the subject splat in the middle of your shot while flying around them, ace!  There’s no way I am that good when filming moving sailing boats with white sails on dark water in a gusty wind.

Matrix metering is wonderful if you have a very uniform view containing no large changes of contrast or colour – sounds like a boring film to me.

Manual control allows you to have a constant exposure over the length of a film segment.  This makes stitching clips together much easier without having a jarring change in quality between the clips.  With a single wheel control on the remote you can control the shutter speed and ISO to match the conditions while in flight.  After a little time and practice you can get better results, containing more information with only a little more effort than is required for auto exposure.

The recorded video will seem a little flatter and more washed-out than an auto-exposed video.  This is because we will be saving more information which can be used in post-processing to balance colour, exposure and create a higher quality finish.

Principle

Using manual mode, we can set the camera up to record a constant exposure but still easily adjust in flight as conditions change.

From advice received and my own experience it seems that the sweet spot is an Exposure Value (EV) of -0.3, ISO 100 and a shutter speed to be a multiple of your video fps.  Why these settings? Well…

ISO 100

This is the lowest sensitivity and therefore the image recorded will contain the lowest noise.  As ISO sensitivity increases, the amount of noise (random speckles) in the image increases because the sensor is working harder to pick-up lower energy light.

 

You don’t have to stick at 100 so if you are having trouble getting the EV up to -0.3 by decreasing the shutter speed, you should switch the ISO sensitivity and then adjust the shutter speed again to get back to the sweet spot.  Before you up the ISO, make sure you don’t have a lens filter fitted which is limiting the amount of light getting into the lens.

You can adjust the ISO in flight using the right wheel on the controller which controls ISO and shutter speed.  By default the wheel should be set to vary the shutter speed so click it in once and spin it to adjust the ISO.  Don’t forget to click it back to variable shutter speed again.

Shutter Speed

Why a multiple of the frame rate?

If the shutter speed is double the frame rate then the shutter opens and closes twice for each frame recorded.  This is just right because the camera software gets an easy choice of what frame to save.  If the shutter speed is 100 and the frame rate 30, the camera has to merge or choose frames to save and that can make the film look “choppy” and/or add strange effects to water, grass and other details.

On the X3, the 4k setting has a max of 30 fps so we should try to keep the shutter speed at a multiple, i.e. 60,120,180.

The right wheel on the control should default to variable shutter speed.  Try not to spin the wheel while you are taking a final recording because you will end up with a jump in exposure a in an otherwise usable clip.

Increasing the shutter speed can make the image crisper, making the focus look sharper, especially for fast moving subjects.  This sounds good but the more times the shutter opens and closes during a frame, the less light gets in.

Why are lower shutter speeds better?

Jelly/jello.  A lower shutter speed creates a more cinematic looking finish where film shot with a high shutter speed looks sharper.  If the speed is too high and the subject moving, like most things we shoot from the skies, the shutter will open and close multiple times as the sensor reads the image.  The sensor is then actually recording different images at different parts of the sensor scan, leading to a slurred image and the jelly/jello effect.  Keep the shutter speed to twice the capture frame rate providing a little sharper image but minimising the slur.

What is D-Log Mode?

Since the X3 only stores compressed video, as opposed to RAW, you’ll need to tell the camera to save as much information as possible. This camera is targeted towards the more consumer end of the market and so it gives you a few auto-options to process the footage as it’s filmed and compressed, assuming the usual consumer will not want to do any post-processing.  D-Log mode has more stops of dynamic range stored into the compressed video file compared to the auto-expose options.  The unprocessed image looks undersaturated and lacking contrast but contains lots of information that is only visible in post-processing, which gives you the ability to recover highlights, shadows or both, but only if you have the right software to post-process.

Filters

OK, so we’re trying to keep the shutter speed at 60 fps and the EV at -0.3 but on a bright day the EV shoots up to 2.0.  To compensate you can up the fps but that could make the film too “choppy” and add a jelly effect – see Shutter Speed section.  Alternatively you can keep the shutter speed low by attaching a ND filter.  The Inspire 1 X3 camera comes with an ND 4 filter and you can buy ND 8 and 16 filters from many places online including Polar Pro, Renaat and Neewer

It’s obviously not possible to change filters in flight and it wastes battery when you have to bring the UAV back to you to change the filter but you will be able to make an educated guess on which filter to start with.  Don’t be tempted to change the filter while the camera gimble is active, it can overload it.

An ND 4 filter should lower the EV by 2.0 or 2 stops, this should help the initial choice a little.

Practical Stuff

DJI GO

If you don’t know what DJI GO is, you probably don’t have an Inspire 1.

There are some suggested settings which are based on talking to experienced cameramen and from Neumann Films who provide LUTs for the Inspire.  LUTs are explained in the Post-Processing section below.

PAL/NTSC

Even if you are based in a PAL region, record as NTSC because you get the extra 30fps setting for lower 4k.

Manual

Set the camera to manual… select the camera settings from below the record button, making sure you are in video mode first.  If you don’t know where these bits are, have go play with the app and fly it a bit then come back to this article.

Switch to manual

 

Set state to Manual and then the initial ISO to 100 and shutter speed to 60.

The M.M bit at the bottom is the EV value – see, it’s the same as the EV:-2.0 at the top of the screenshot.   The EV of -2.0 means that the image is underexposed, that’s because I was inside in quite a dark room when I took this screenshot. This matches the histogram, the box next to the map, which shows a lot of dark, spike on the left with a big X on top, and no mid or white, no bumps or spikes on the right.

Video Size

The smaller 4k with 30fps.  If you don’t see an option for 30fps, you still have the region set to PAL, change it to NTSC.

Video size

Colour Style

Neumann Films suggest a custom colour style to work best with their LUTs, sharpness -1, contrast -3 and saturation -3.  This is more personal preference and dependant on what scene is being filmed.

Colour properties

Summary

Finally you should have something looking like this:

Camera Settings Summary

 

Time to fly

Red Bridge

Part of your pre-flight check should be to check the ISO and shutter speed at 100 and 60 respectively.

Take off and fly your planned route, balancing the EV at -0.3 while you fly by adjusting the shutter speed using the right wheel on the remote control.  If the wheel changes the ISO instead of the shutter speed, click the wheel in once and then try again.  Remember that spinning the wheel up towards the aerials will increase the shutter speed and therefore lower the EV.  The wheel does not change the EV directly so don’t spin the wheel up to change the EV up!

You should be able to find a shutter speed that keeps the EV at -0.3.  If it’s continually to high, then try an ND filter.  If it’s too low, you’ll have to up the ISO, adding noise.

Once you’ve got the settings right for the required flight plan, you can go record the actual film you want, keeping a steady exposure over the whole shot.  Remember, don’t change the shutter speed or ISO while filming the final shot else you’ll end up with an obvious jump in exposure.

Sunet BridgeMost importantly, safety first.  Don’t crash your UAV while you are concentrating on the camera.  It’s better to get your Inspire back in one piece than it is to have to learn to scuba dive to retrieve what’s left.

Please add comments, improvements, thoughts and links to your videos below.

Thanks to the lake_flyer and the other chaps over at inspirepilots.com for their help and advice.

Thanks to you for reading and happy flying!

Further reading

Separate Camera Controller

The Inspire 1 allows you to fly the UAV while a linked remote control can control the camera.  The video quality produced by two people is more than twice anything a solo pilot can do.  The video will be smoother, the subject easier to frame and the flight safer.  It will also take less time to find the correct exposure sweet spot.

Post-processing

More detailed article coming soon but balancing the colour and applying colour grading, either manually or using LUTs will make the dull video into vibrant, well balanced video that you can be proud of.

Histogram

The X3 does not have a huge exposure range so you’ll have to keep an eye on the histogram as well as the EV level.

Show histogram

 

The histogram is a whole subject in it’s self and is much more of an art than a science, though you’ll need a physics degree to understand it fully!  As a rule of thumb, if you see large spikes on the histogram, especially near the edges, your image is under or over exposed.  If you want to learn more, I’ll be adding an article or video about using the histogram while flying very soon….

 

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