We are currently limited to the stock ND filter from DJI until they or a third party release stronger ND filters. Some have gone the route of buying ND filters with the appropriate filter thread size, but there has been questions about added weight to the camera and gimbal.
I decided to go with a sheet of ND gel.
I went to an expendables store and purchased (1) 48" x 21" sheet of Lee 210 0.6 ND gel (Cost =$8)

I then got a circle cutter and cut out a circle the same size as the DJI inspire 1 filter and placed it in between the camera lens and the filter.

I think it works pretty well. with the Stock DJI ND filter which is also a ND4 / 0.6 ND, when doubled up it makes it an effective ND16 / 1.2ND

Questions? comments? Let me know what do you think:

Here are the results:
.
Shot at 4K 24FPS,
ISO 100,
Shutter 50,100, and (800)
12PM on 4/2/2015


more tests. details in post below.

What circle cutter do you recommend?  Do you notice any extra flare when pointed toward the sun?

I bought an X-Acto circle cutter from an arts and crafts store. cost me $10. It worked ok, enough for me to measure it out and get an outline, I also had a scissors on hand.

Since this was all a test I didn't want to spend a lot to find out it didn't work.
As far as flare, your still going to get blown out looking at the sun at ND16, but I didn't notice any extra flare. Since it's so close to the lens the camera doesn't see the gel. If anything, the image is ever so slightly softer. which may not be a bad thing with the over-sharpness the inspire is set at by default.

Very cool, thanks for posting.   

In a perfect would I prefer to not stack ND so I think I'll get some 1.2 and put it in and out of the clear filter.   Having said that I might get tired of it and be better off taking the same approach as you with .6.

Thoughts?

jimhare Posted at 2015-4-3 12:54
Very cool, thanks for posting.   

In a perfect would I prefer to not stack ND so I think I'll get s ...

Hey Jim,

I'll try another test tomorrow stacking two cuts of the ND 0.6 in the clear filter and see what happens. Otherwise I agree, trying to stay away from stacking multiple ND's is probably better overall.
The shop I went to had .3 .6. .9 and 1.2 sheets. but of course you can buy them all online.

The only other thing I could think of at the moment is that technically these ND sheets are made more for lighting purposes. There is bound to be many more imperfections on a gel sheet than a proper ND filter, hand holding a tiny piece of gel can be a pain in the field.

LEE Filters ND Guide
209: 0.3ND
210: 0.6ND
211: 0.9ND
299: 1.2ND

Mkell_CA_SF.BAY Posted at 2015-4-3 13:24
Hey Jim,

I'll try another test tomorrow stacking two cuts of the ND 0.6 in the clear filter and s ...

Yeah, I had the exact same thought about it being lighting gel.   But then again you basically can't see any imperfections with it right up against the lens.

Same reason no one is too fussed if a lens has cleaning marks or a small scratch on the surface, it's generally imperceptible.

You're right about not wanting to handle it in the field.  I suppose in a perfect world you would have an extra clear filter and make your own 1.2 from a single gel.  

Still, your initial test looked great and I didn't notice any problems stemming from  stacking the NDs.

Do you think it was enough to block even the brightest light and maintain a 180° shutter?

This is cool, thanks for posting this.  I'm going to order a sheet and give it a shot.

Just a cautionary note here: I bought a set of ND's online at Amazon:

K&F Concept 37mm Slim HD Multi-Coated Variable Fader NDX Neutral Density Adjustable ND2 to ND400 Lens Filter + Microfiber Cleaning Cloth for DSLR Camera.

37mm thin profile with male and female threads so you can stack them is what I was thinking. The thread pitch isn't quite right. They do hang on but I think will eventually wreck the threads on the camera so they are a no-go.

Don't know what the thread pitch in the Inspire camera is but it appears to not be what is standard.

Tim

wolftj@mindspri Posted at 2015-4-4 03:05
Just a cautionary note here: I bought a set of ND's online at Amazon:

K&F Concept 37mm Slim HD Mul ...

Tim, concensus thinking is that it's very unlikely we'll find a threaded ND that will fit the Inspire, which is why we are going down the road of cutting ND gels and placing them in the existing supplied filters.

I know a couple of people are looking at manufacturing their own threaded filters for the Inspire but don't know how far along they are.  

If you do find a solution please let us know.  

jimhare Posted at 2015-4-3 14:25
Yeah, I had the exact same thought about it being lighting gel.   But then again you basically can ...

Hey Jim, I like the idea of having an extra filter for the gel. Not sure if clear filters are being sold separately yet, I think the stock pairs go for $40. And as i'm sure you know this is hopefully just a stop-gap method of dealing with our ND issues until a proper filter set gets released.

Maintaining 180° shutter is certainly easier, i've noticed when the camera tilts down into a shadowy area you may lose a stop or two in some cases/ tilting up and of course shooting in direct sunlight is still going to blow the image out.

Right now I'm handling it via tweezers so not to hold it with my fingers or get dirt on it. The gel is a snug fit in the filter, but it's very forgiving, it does not have to be a perfect circle.

wolftj@mindspri Posted at 2015-4-4 03:05
Just a cautionary note here: I bought a set of ND's online at Amazon:

K&F Concept 37mm Slim HD Mul ...

Hey Tim,

I've read about users finding the right threads and being able to stack them onto the existing camera/threads. I too am worried about the longevity of the camera threads themselves, I take my time making sure I don't cross thread or tighten too soon every time I screw the filter on.

With the gel, at least its super light so you can stack much more ND without having as much of a worry about weight.

I did another test today. Still working off the .6ND gel. This time I double and triple stacked cuts of the gel into the DJI stock Clear filter.
Heres the video:

I tested x3 stacked .6ND= 1.8ND or a ND64 filter (6 stop reduction) we would most likely not have to shoot with this much ND, but I had it on hand so why not.
I found I had to crank up the ISO for the first time to 200, otherwise it was a bit underexposed.

Next I tested x2 stacked .6ND = 1.2ND / ND16 (4 stop) against a clear filter with no ND at a high shutter ~1250

Finally, and all admit this is not exactly a scientific test, and I should have shot at 4K 30FPS instead of 4K 24FPS,
but I tried to get the correct exposure between the two filters.
.
the current Inspire 1 camera has a fixed 2.8 aperture.
So If my math is correct:
Four stop reduction would make it a F11 equivalent.
1/60 shutter at F11 is equal to 1/1000 at F2.8.

Here are some screen grabs:

Mkell_CA_SF.BAY Posted at 2015-4-4 12:53
I did another test today. Still working off the .6ND gel. This time I double and triple stacked cuts ...

Hi there,

Thanks for doing all the tests for the ND filters.
I am thinking of getting some gels but am wondering what the overal consensus is on what is enough.
Lee filters appear to be much easier to find that the Kodak ones, even online.
Would a .6 and a .9 do the trick?  Would I be better of getting a 1.2 instead or as well?I am trying not to double up as I am concerned about the distortion and the technical aspect of cutting and inserting them without any hand handling - especially while out in the field.
I, also wish, that dJI would have thought of all this before hand so we had different ND options and/or T least a common thread so we could purchase filters with a bit more ease.
Cheers,

Peter

Sky High Aerial Posted at 2015-4-8 23:21
Hi there,

Thanks for doing all the tests for the ND filters.

This is what I am considering purchasing:

Lee .6ND, 20x24 2 Stop Neutral Density Lighting Filter
LEE FILTERS 211 SHEET .9 NEUTRAL DENSITY SHEET Gel-Sheets
12 ND Gel Sheet 299 (Neutral Density)

Good?

Great work Mkell,

An innovative approach to the issue!

Sky High Aerial Posted at 2015-4-8 23:33
This is what I am considering purchasing:

Lee .6ND, 20x24 2 Stop Neutral Density Lighting Filter

I have been playing around with different intensities of the gel and seeing what works best.

Here's what I found so far:
The stock ND filter from DJI is equivalent to ND4 (that is the same as .6ND)

You can stack cuts of the gel, but there may be a slight degradation in sharpness... still testing that out, but its important to note... this isn't so bad as the inspire default sharpness is already a little too sharp

Lee 1.2 ND is equivalent to ND16( twice the strength as ND4) I think this is the sweet spot for shooting with, you can shoot at 1/50 1/60 shutter speeds and get a pretty good exposure. However, if it is still very bright, or you are shooting in an area where the sun is reflecting back, your highlights will still clip. thus you need to up your shutter speed to 1/80 to 1/120.  I've not had to shoot a higher shutter speed than that.

Also, when you are shooting straight down with your camera you lose a stop or so of light, so even at 1/50 sometimes its just a little underexposed in the shadows. In these situations I would either switch to the stock DJI filter, or go with ND 0.9.

So while you can shoot with these I would say, don't stack the gel if you don't have to and think about what shots you want to get where. sometimes you just have to find that happy medium.