I ran into a gimbal issue when using some ND and ND/PL filters on my Mini 2- and wanted to share some things I think I've learned.  Things were going great on the first few trial runs, swapping filters, etc.  But as I was landing on about my third or fourth run, I thought I heard a high pitched squeal coming from the drone, and sure enough as soon as the props stopped it was completely obivious and very loud.  Turned off the Mini 2 and of course the sound stopped.  Turned it back on and the noise returned, and was obviously coming from the gimbal.  Turned back off, and took the filter off, and thankfully upon startup, no sound. The issue occured when I was using my ND/PL 8.

I was home, so jumped online to investigate.  Sure enough, there's a bit of dialogue out there about similar Mini 1/2 gimbal/filter issues with noise/shake, etc...  adding filters adds weight, causes gimbal to squeal/vibrate , etc. (although, I didn't experience vibration at first, but definitly did later when I replicated the scenario a few more times).  It all kind of made sense to me, and I was obviously bummed, because I wanted flawless performance while using filters on my Mini 2.

But the reason for my post is more to wrangle some of the confusing information I came across online... and hopefully someone with the same exact issue will find my analysis useful.

It appears a lot of filter companies haven't changed their filter design between the Mini (1) an Mini 2- and just say they work on both.  And it appears the Mini (1) doesn't run into this issue nearly as frequent as the MM2s out there- and subsequently, when reading most of the forums threads, you don't know what drone (1 or 2) the person is talking about, and all the 'mine works fine' vs 'mine's shaking/noise', etc.  becomes a moot point if you don't know which Mini (1 or 2) you're taking about.  Also, there's tons of different filter brands out there for the Mini (1 and 2 or both) so without knowing, who's to say which one's cause it, and which don't.  Also, some are just ND.  Some are ND/PL combos or CPL with a rotatable ring.

Many articles/youtubers rave about using ND filters, specific brands, etc., but none really seem to address any gimble noise issue specifically on the Mini 2.  DJI didn't design the MM1 or 2's to utilize filters, so they (rightfully, so) get to stay clear of figuring it all out.

Notice however, I haven't mentioned what brand of filters I tested...  but I don't think that's the issue, and here's why:

I think the issue is completely related to the weight of the filter, and what version of Mini you have.  And the weight is heavily (pun!) determined by wheter it is a simple ND filter, or has the CPL/PL ring on it.  Because, NONE of the simple ND filters I used seemed to cause the gimbal noise. It was only the filters with the rotatable rings that caused the gimbal noise to occur.  Now, some folks online say you have to put the filter on perfectly, or you might have issues.   Well, I tested it several times- getting it on perfect sometimes and more perfect other times, and sometimes there would be NO noise, sometimes two minutes into launch it would start to squeal, sometimes immediately on power up it would scream or slightly whine...  with or without perfect placement of the filter.  One thing for sure though, it was always the CPL with rotating ring ones that it happened with- IF it happened- regardless of how perfect I got the tiny thing on there.  So far, all the simple ND filters (no ring) I used, haven't caused the gimbal to squeal.

When I weighed the filters, all the simple ND ones came in around 0.95 grams, while the CPL/PL filters with rings were about 1.06 grams- I'm assuming the ring mechanism and two layers of glass account for added micro weight.  I am waiting for two other sets of (different brand) filters to arrive, but I think my assumptions will be correct...

If you have a Mini 2...
And are using a ND /CPL combo filter...  
The gimbal may likely squeal and perhaps even vibrate...  MM2 + ND/CPL=
But the non-CPL filters (smooth glass, no ring, ND) seem to be okay (if mounted correctly)...  MM2 + ND=;)

ALSO, I'm going to go out on a limb and also say that it is probably anything that weighs more than 0.95-1.0 grams that may cause issue for my Mini TWO gimbal.  WARNING- that's my prediction/assumption ONLY, based on limited testing and the food scale I own.

I'll keep testing and weighing when the other filters arrive, but my assumption is that I won't be able to use any of the ringed filters on my Mini 2.  And my conclusion will probably be that I can only use filters that weigh less than 1.0 grams- ring or no ring on MY MM2.  I'm stressing MY mini, because I came across one thread where a person said that all the gimbals on all the MM2s out there are different, and may have different tolerances for how much added weight they can sustain.

I had a hard time finding a definitive answer for my exact MM2 + filters scenario. Hopefully this all helps anybody else running into this same issue- specifically with the Mini 2, and specifically with the CPL ringed filters.  If someone out there has done any thorough testing which completely contradicts or debunks what I'm saying above, please chime in- I haven't seen much out there in terms of testing the differences in Mini 1/2 gimbals vs filter types (ND vs ND/CPL)- beyond image quality.  Or, if you use a MM2 and successfully do use CPL ringed filters without issue 100% of the time- please share!

I'd love to be wrong, as I was really looking forward to using the ND filters in conjunction with a polarized effect.  But if I can only use ND and have to forego polarization- that's the option I would prefer most.  Half win?

Anyway- that ALL said... my question to anybody out there:  That high pitched gimbal squeal- obviously not good.  Should I be concerned I did damage?  Everything seems fine and in working order, and it probably only occured for a combined total of 15-30 secs that I'm aware of (although it could have been going on the whole time I was flying before I noticed it- maybe 2 min?).  It hasn't occured at all when I fly without a filter, and it now only occures when I briefly test/replicate it with the suspect ringed filters.  

I'm more curious if one were to add the filters that cause the noise issue, and fly prolonged with the gimbal squealing like that, what damage would be expected?  Eventual burnout, or absolutely fine?  Stay safe- or live crazy?!  Fly it 'til it breaks, or preserve it forever!

Oh- I'll add...  it was cold outside when it first occurred (34 F/1 C).  But I was able to replicate the issue/noise indoors (room temp) just fine.

I have Skyreat ND/CPL filters on mine with zero problems!

I have freewell ND/CPL  filters and sometimes the problem happened.
I think has to need more weight on the opposite side of the camera for balance it.

Freewell filters here and not had an issue with them.

DAFlys Posted at 11-19 00:48
Freewell filters here and not had an issue with them.

Thanks DAFlys! Glad to here they work for someone.  Are they the Freewells with the polarizing rings?

fans8489d44d Posted at 11-18 14:02
I have freewell ND/CPL  filters and sometimes the problem happened.
I think has to need more weight on the opposite side of the camera for balance it.

Hmmm...  maybe you're on to something.  With the polarizing ring predominantly on the left side of the filter, it could  be throwing off the balance from side to side, just enough to upset the (gimbal) universe.  Thanks.

Mobilehomer Posted at 11-18 13:32
I have Skyreat ND/CPL filters on mine with zero problems!

Lucky, i have been put off by all ND for the Mini 2 because of 2 reasons, 1 is reviews regarding gimbal issues, it looks like its pot luck as to whether or not it will happen to you..

Skyreat

The Freewell 8 pack has the better reviews but damn, £130 over here, that's the other reason I've stayed away from them lol whilst you can buy smaller packs but then you end up with multiple cases

Tiffen filters use superior glass, and that's what it's all about.  Never an issue.

https://tiffen.com/pages/mavic-mini-edu

hunterws Posted at 11-20 11:07
Tiffen filters use superior glass, and that's what it's all about.  Never an issue.

https://tiffen.com/pages/mavic-mini-edu

Perhaps not, have you followed that link lately, then click buy?

Bashy Posted at 11-20 14:42
Perhaps not, have you followed that link lately, then click buy?

wow, I hadn't.  Looked through the site and they no longer offer them.
That makes my 2 sets of 6 even more valuable  =)

Looks like they're sticking to more high-end drones

They can still be had. https://www.amazon.com/Tiffen-6- ... Mavic/dp/B085FXYS49

Update- may have solved my own issue...?

gokufly Posted at 11-23 09:58
Update- may have solved my own issue...?

I ran a gimbal calibration with one of the problematic filters installed.  The bad sound reoccured even after that- so I took the filter OFF and did another gimbal calibration.  

The other (brand) PL filters arrived and they did not cause the gimbal to squeal.  I was curious, so I put the 'problematic' PL filters back on, and have not experienced the gimbal sound at all yet.  !?!

So maybe the two gimbal calibrations I ran back to back, first- with filter on- then again- with filter off- did something that solved my issue. ???

Anyway- that's my update.  Now, my problem is to decide if I want to keep both (brands) sets of PL filters.  I'll probably fly a bit more, just to see if the issue shows up again.  If it does, I'll see if the duo-calibration trick solves it.

gokufly Posted at 2021-11-23 10:09
I ran a gimbal calibration with one of the problematic filters installed.  The bad sound reoccured even after that- so I took the filter OFF and did another gimbal calibration.  

The other (brand) PL filters arrived and they did not cause the gimbal to squeal.  I was curious, so I put the 'problematic' PL filters back on, and have not experienced the gimbal sound at all yet.  !?!

Have you used the Freewell brand?

I have noticed they have very recently changed their design of the CPL filter. You can see on their website, it no longer uses the two small hooks but instead looks more like the other brands. I contacted them about it and they confirmed this and said the new design is lighter. Unfortunately I haven't been able to find any reviews or videos of the new design - everything on YouTube is the older design. I have heard many complaints about the previous design slipping off easily so I'm hoping the new design also fixes that and hopefully prevents gimbal motor issues.

Jokkydee Posted at 1-30 17:43
Have you used the Freewell brand?

I have noticed they have very recently changed their design of the CPL filter. You can see on their website, it no longer uses the two small hooks but instead looks more like the other brands. I contacted them about it and they confirmed this and said the new design is lighter. Unfortunately I haven't been able to find any reviews or videos of the new design - everything on YouTube is the older design. I have heard many complaints about the previous design slipping off easily so I'm hoping the new design also fixes that and hopefully prevents gimbal motor issues.

I just checked out their site- and yup, the mini1/2/SE filters got a redesign.  Hmmm.  Thanks for the update Jokkydee.

I didn't want to name brands until I could absolutely confirm which ones were causing the issue- but the Freewell ones (old design) were actually one of the culprits.  I'll have to check out the re-design. Their website is listing them as 'gimbal safe', so maybe they addressed the issue.  Sweet- I love it when brands do that.