Mixing formats for VFX work
Has anyone any experience using a DJI inspire drone to film plate shots to mix with Alexa footage?
I am planning a shoot with a stunt on top of a roof. However we cannot access the roof, so we will set build the roof... and use blue screen looking down for the over shoulders shots (which there are 2) The rest will be shot against clear real sky.
The drone company are suggesting using the DJI for stability (the location is windy) not for cost reasons of flying a mini. The editor would prefer using an Alexa to match. The VFX supervisor seems ok mixing footage. I am being asked to make the final call on using the DJI drone, or flying a mini... Everyone seems keen to use the DJI. My other concern is matching angles and camera height with the drone.
Any thoughts on these points I would very much appreciate to hear from anyone.
All the best.
Hello-toggle quoted message. . .
I’m a DP/drone pilot with an Inspire 2 X7 system. I do believe it would be safer flying the Inspire than a mini. I don’t know about stability to wind as it’s a big copter to hold the weight.
The gimbal on the Inspire is really incredible in the wind. The risk reward doesn’t quite make sense as the cost of mini/lenses as compared to the Inspire system which is pretty stable in the wind. Generally - the Inspire system is simpler to get up in the air and get the shot. (In my opinion!)
Shooting with Cinema DNG with the X7 super 35mm chip - you should have plenty info/detail for matching. I just finished a big budget feature and one of the shots was a BKG to be stitched together as a crane extension in the sky. They contacted me b/c of the set up I had so I think it probably would be fine for your needs.
Let me know if you have any questions. Best of luck!
On Jul 28, 2018, at 9:08 AM, Thomas Hines <tomhines57@...> wrote:
If they’re using the X7 camera, on an Inspire 2 it can work great.
It’s a super 35 sensor size, can shoot RAW and has pretty good dynamic range, considering how small and low cost it is. They make some very nice carbon fibre S35 lenses for them too, reportedly designed by Hasselblad (who they now own).
I’ve done green screen comps from the air in daylight in daylight that have worked out well.
For me, I always think matching is less of an issue in these scenarios. You’re not doing close ups, they’re environmental shots and with VFX elements on top. Resolution and dynamic range gives away the match first in that scenario.
I have gone towards requesting for setups like this over flying an Alexa. They have a much much longer flight endurance and it seems slightly less risky in terms of camera loss and safetly to me than flying an Alexa when the drone is so much smaller. Find I can get more shots done faster using something like this setup over flying a full size camera.
The real key is finding a good pilot / operator team. When you fly the big rigs, the pilots tend to already be much better. With the Inspire 2 operators, they are often cowboys.
You’re best off finding an experienced team that fly the big rigs that have the inspire 2 as an option, which is maybe what it sounds like in your scenario.
By flying a mini I’m assuming that you mean flying an Alexa Mini vx flying an Inspire. I have an Alta, an Inspire, a Phantom 4 Pro Plus, a Mavic Pro and a couple of tiny fpv drones I use for practice. I also do a bunch of visual effects work. Here are the considerations you need to be thinking about.
1. Weight of the drone because weight is mass and mass is inertia. If you are parking a drone in the sky or moving it then the more inter you have the smoother the shot will be until you consider:
2. Rotor loading. Rotor loading is the total weight of the drone divided by the square inches of the rotor disks. The higher the rotor loading the less effect wind gusts are going to have on the drone. Rotor loading + mass gives you a prediction of the stability of the platform in the sky and for VFX plates keeping the camera steady in space is extremely important and it has nothing at all to do with the effectiveness of the gimbal. There is one more thing to consider:
3.Reserve power. The GPS will try and keep a hovering drone in one spot and if you have a decent GPS lock and but the power to weight ratio + rotor loading + mass are not right then the drone is going to have a very hard time staying in one spot or even moving smoothly. On the top of a tall building, with all the gusts, there are going to be a lot of parallax changes that you have to watch out for. They are incredibly difficult to correct.
Now let’s talk about matching lenses. Since you are using a green screen where most of the background will be replaced, as long as camera position is approximately the same as the position of the camera that films the actors the perspective will work. All you need is a lens with very little distortion that is wide enough to fill the frame. If you shoot the actors with a lens that has an angle of view of 36º (a “normal” lens for the sensor or film size) and the camera is 10 feet from the actors and above them 2 feet then the drone is going to have to be 10 feet away and 2 feet above where the actors wold be standing if they cold be on top of the building or the perspective isn’t going to be a good match. You can cheat quite a bit if there are no props like railings behind the actors, but if the director wants to include physical props in the shot it’s important that you match position and angle.
Now let’s talk about flying an Alta or similar with a good gimbal like a MoVI Pro vs an Inspire. The Alta has 18” rotors and is probably going to weigh in at about 30 pounds. If it is an Alta 8 then it’s going to have a lot of reserve power. The Inspire with a camera is about 12 pounds. The props are 15 inches and there are only 4 of them. I’m not going to go through the math but in my experience the Alta, with it’s greater mass and more propellers has the edge in windy conditions by a little bit. The Alta is a lot more powerful and has a lot more rotor area so, given exactly the same conditions and equal GPS signals and equally effective flight controllers, the heavier drone is going to stay put in the sky. On the practical side however, unless the gusts are changing more than 7 or 8 knots, like wind 10 gusting to 20, you won’t see much of a difference. If you flight waiver is limited to a few hours and there is any chance of winds above 7 or 8 knots I’d go with a heavier drone. If the drone has to bee flown manually and the operators skill is high then a larger drone is going to have the advantage.
I hope I haven’t bored you. I will put the Mavic much closer to an actor than my Alta, not because it’s more stable, but because it’s way more responsive because it doesn’t weight anything and if I did have an accident it would do a lot less damage, but when I need maximum accuracy I pick the Alta or the Inspire, depending on the weather conditions and the shot I need. Jon Swindall recommends the Inspire but I would probably go with the Alta for the reasons I have already stated.
I don’t think you’ll have any real trouble with either system, and matching footage, to get the look, though it can be difficult, isn’t nearly as difficult a problem as trying to correct for a miss framed shot or fouled up perspective.
MovI Pro / ALTA / Licensed Commercial Pilot Fixed Wing and UAV
Hi Thomas,toggle quoted message. . .
We’ve got an Inspire with X7 and the primes down here in Bournemouth if you want to borrow it for a test.
Have also shot some statics with charts in recently, usually helps to convince post people.
Drop me an email and I can help out.
Director of Photography
+44 7404 5454 02
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