Paul C. Buff, Inc. Technical Forum

I'm going to use a CyberCommander to try and work with a DJI drone camera which is also radio controlled to its shutter. Problem is there is no flash sync socket on the drone's remote.

However, knowing the drone's shutter lag of me pressing the button on its remote to the time the image is recorded looks to be 1/132 sec or 8 ms. for the radio communication and triggering of the camera for still photos.

If the radio time of the CyberCommander is 1/1250 or ~0.8 ms from the Tech Board here, then I would need to put in a lag time of 0.072ms to make the two units sync.

Using an Arduino microprocessor I could wire it so two triggers, one going direct to drone's shutter release button's switch and the other to CyberCommander socket, could work by lagging the CyberCommander by the 0.072ms amount to sync them together.

Does this seem feasible?

Fwiw, I am trying to use the drone as an aerial camera on a tripod for stills in conjunction with fill flash. Just park it in hover and steer the camera's gimbal to the area where the ground-based flash units are located. Too bad there is not a sync socket on the drone's RC unit or built wirelessly into their software somehow.

Tia.

Mack

If you can time the delays right, I can see that it is conceivable this could work.

However, depending on the camera used (and TBH, I am not familiar with DJI's offerings), there may be sync issues with it, depending on if it is an electronic shutter, or a mechanical shutter, and the types thereof.

Thanks. I think it's time to prototype something.

The test drone is a DJI P4 which has a rolling shutter. The newer "P4 Pro" has a mechanical shutter but it is in short supply being new. Their new Inspire 2 with their 5XS RAW camera is a rolling shutter too, while their cheaper 4XS is mechanical. The 5XS is a a larger sensor over the smaller 4XS mechanical one. The 5XS is a Micro 4/3 sensor.

I would guess the shutter time for flash coverage might be related to the video speeds of 60 frames per second (1/60 sync) or maybe higher. Don't know until I get the CyberCommander and it wired up and see if I get partial sensor coverage. Might be the Still Photo speeds are higher (Their cameras go up to 1/8000 sec.).

Would be nice if the things were linked wirelessly to the Buff remote triggers as they use the 2.4 and 5.8 GHz spectrum. Maybe somewhere down the line they'll do this in their SDK kits they provide to the app developers.

Mack

Update to anyone interested in this is that it can be done with some limitations.

The DJI Phantom 4 uses a rolling shutter so the scan time top to bottom is long regardless of the shutter speed being set to as high as 1/8000. The full-frame scan time is about 1/12.5 seconds on it to sync and cover the frame. CyberCommander has to be delayed by about 176 milliseconds to that of the shutter signal to the drone.

To do so, I just paralleled a mini jack off the transmitter's release button and fed it to an Arduino Uno with a Relay Shield from Radio Shack: One relay triggers the release (parallel) mini jack for the drone's shutter, and second relay is the delay for the CyberCommander into its mini-jack port.

DJI has a mechanical shutter in the newer 20 MP Phantom 4 "Pro" model and also the same coming out in the Inspire 2 with the 4XS camera on it for stills. Their more expensive X5S camera (i.e. a 4/3 sensor with interchangeable lenses.) is also a rolling shutter as well and scan time may be long with it too as with the older P4 model I used. I don't know how their mechanical shutters operate to come up with maybe a faster sync speed.

Also, the frequencies used between DJI and the CyberCommander may overlap. I found if I turned the DJI stuff on first, and then the Buff stuff, the DJI would automatically change its frequency to a clearer signal. Otherwise you might see a "No transmission signal" red error window on the DJI GO software screen. Maybe changing the CyberCommander to some other channel would help too, but I just installed the AAA battery in the CC once everything with the drone was happy and that seemed to work.

Added:
Did a test with a W.L. Ultra 1200 and the Buff 11" long throw reflector in noon sunlight. To get the slow 1/12.5 sec. exposure in sunlight, I added a ND-64 filter to the P4 drone's lens and it's exposure meter was happy with that. With the above flash, I got a nice 1:2 fill at a distance of ~20 feet at full power. So it was a success, even with the slow speed of the rolling shutter.

I got some misfires with the CyberCommander and drone. The DJI drone constantly scans the 2.4GHz frequency range automatically for a good frequency to lock onto, and I suspect the CyberCommander is also operating in the 2.4 GHz spectrum and maybe on the same channel as the drone might be at a given time so it might occasionally misfire if the signals overlap.

Question:
I can set the drone's transmitter frequencies Manually (No Auto scan.) and away from the channels in the CyberCommander if I knew what the frequency and channels in the CyberCommander are.

Is there any information on the frequencies and channels used by the CyberCommander that are available to allow me to set the drone transmitter manually and away from the CC frequencies?

Thanks.

Mack

In the SETUP screen, go to FREQUENCY, and select your frequency (FREQUENCY 01, 02, 03, ect.)

This screen will also display the exact frequency (in GHz) of the selected frequency.

Thanks!

Mack

I found the cross-channel frequency error in the following table. I had the CyberCommander set to Channel 13, and the DJI drone was set manually to Channel 19 (DJI only allows 8 channels to be manually set.). I put my error in bold below which was by pure chance today that they were on the exact same frequency, although both having differing channel numbers. I had used the Auto frequency selection on the drone prior, but it occasionally would not allow the CC to fire so I moved it off to Manually set which seems far more reliable.

So today, by freak happenstance, both turned out to be the exact same 2.451 GHz frequency so the CC refused to fire as the DJI was likely the stronger and constant signal source. I moved the drone to DJI Channel 13 (2.391 GHz) and the left the CC on Buff Channel 13 (2.451 Ghz.) and it began to fire every time like it should. :mrgreen:

CyberCommander channel, followed by Frequency (GHz)
1, 2.427
2, 2.429
3, 2.431
4, 2.433
5, 2.435
6, 2.437
7, 2.439
8, 2.441
9, 2.443
10, 2.445
11, 2.447
12, 2.449
13, 2.451
14, 2.453
15, 2.455
16, 2.457

DJI Phantom P4 channel followed by Lower, Center Frequency, and Upper Frequency band (GHz):
13, 2.381, 2.391, 2.396
14, 2.391, 2.401, 2.406
15, 2.401, 2.411, 2.416
16, 2.411, 2.421, 2.426
17, 2.421, 2.431, 2.436
18, 2.431, 2.441, 2.446
19, 2.441, 2.451, 2.456
20, 2.451, 2.461, 2.466

There appears to be some overlap of the channels in DJI's setup so one has to be careful with them.


However, I have one question on the CyberCommander:
How or what does setting the flash "Group Number" on the CC do to the set Frequency if anything? Any overlapping?

Tia.

Mack

There is no difference in frequency setting whether it is Group or Channel.