Well, DJI list Sandisk as being a preferred brand. There are many different brands around and many of them meet the stated specifications and will be more than good enough of course but Sandisk are listed by DJI, they're relatively cheap and available everywhere, you just need to be careful of fakes when buying from unknown online vendors.
I have, well I don't know how many I have but across the fleet of aircraft I have one card per battery per aircraft, (I'll get to that in a minute) I have 7 aircraft each with multiple batteries so it's a lot. I started off buying Sandisk extreme but now days the Sandisk Extreme Pro are becoming very common and that's what I buy. I have not had a problem with either in any aircraft but with the air being rated at 100Mbps output faster has to be better right?
As to size, my viewpoint is a little different to most. I don't buy big cards. Part of that is because I am flying commercially most of the time. If I am out flying a 5 hour job and recording the whole days work on say a single 128Gb card and I lose the aircraft on the last flight of the day that's upsetting but I am insured, I'll get the aircraft replaced eventually. If I lose the whole day of footage that's more than upsetting. it means I have to do the whole job again from scratch. At the best the job for the customer is going to be delayed, At worst I lose a customer. Sometimes the value of the footage represtents more than the cost of the aircraft. Even recreational pilots sometimes remark that losing the great footage as well as the aircraft was adding insult to injury.
The other reason is there is some anecdotal evidence that larger cards fail more often then smaller cards. Now, although I am a tech by trade I've never actually taken time out to make records and test this and I can't say as I've really noticed myself but it's a common theme among some people. Our old friend from "Drone Valley" of YouTube reknown bangs on about that quite often. He's been flying R.P.A. longer than me so maybe he knows.
A 32Gb card will hold about 40 minutes of 4K video give or take, the
Phantom 4 Pro v2 or
Mavic 2 will fly for around 30 minutes under perfect conditions. I buy 32 Gb cards and I change the card whenever I change the battery. I have a written pre and post flight checklist for each aircraft and I and my employees follow them. I have it specified "Change Micro SD card along with battery". As I take them out I put them in a holder in order and at the end of the day I have everything I did in flight by flight order which makes it easier to find the footage/stills I am looking for. They are ridiculously cheap and I haven't had one die on me yet.
Just me $AU0.02 worth of course, as long as it meets the specs in the end any reputable card will do the job. I take safeguarding my images as I go a little more seriously but as I have outlined above I have a reason. If it doesn't bother you then by all means buy one larger one and fly all day.
Regards
Ari
