Feedback Variable ND Filter Trouble

KillRamsey

Super Moderator
Jun 20, 2012
124
Hood River, OR
Kyle
This is probably something simple, but it's my first variable ND filter experience, and it ain't going so hot so far. I stopped this morning on the way in to work, set up a tripod, put the 14 on the XT, and took this. I noticed it on the rear LCD, and thought "uh oh. Maybe it's just on the LCD and won't be on the image?" But of course it is.

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Lightening up the ND filter to around 4 stops, it diminishes but isn't gone...

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So what causes this? I know about circular vs linear polarizers, but have never heard of ND filters having the same potential issue.
 

Luke

Super Moderator
Nov 11, 2011
214
Milwaukee, WI USA
Luke
I haven't seen this before, but think about how a variable ND filter works (not that I really know), but it is 2 polarized pieces of glass rotating and the various levels are from the resulting darknesses of the 2 different pieces aligning. Not sure if you were just "between" two settings or if it defective. I'd set up a tripod and fire off a few shots at different settings and see if you can have any success. If you can't (or it isn't easily repeatable every time), I'd send it back and get a 10 stop ND filter from a quality filter maker for when you need the "effects". And then a 3 stopper for more normal uses like shooting wide open in sunshine.

p.s - the second shot shows dust spots on your sensor in the sky. (sorry for the misplaced metaphor {or is that a dangling participle}....obviously your sensor is not in the sky)
 

Pim

Regular
Apr 21, 2012
68
Eindhoven, The Netherlands
Pim
I very briefly owned a variable ND filter and got the exact same effect with anything above 3 stops or so... I did some research and found I was not alone in experiencing this. Maybe the filter was not of sufficient quality (I cannot remember the brand but it certainly was not the cheapest one), but needless to say I returned it and got a fixed filter instead.
 

KillRamsey

Super Moderator
Jun 20, 2012
124
Hood River, OR
Kyle
Luke the dust is on the filter. It showed up on several shots, and vanished on others as I rotated the filter around. So it's on the front element somewhere, but because the damned thing is so dark I didn't notice it was smudged. I blame my 4 yr old. And I tried shots all the way from full 8 stops to just 2 stops, and the effect gradually comes on in a smooth manner. So it's not at just one specific spot in the range of filtering.

Crap.
 

Luke

Super Moderator
Nov 11, 2011
214
Milwaukee, WI USA
Luke
Kyle, if your front element is smudged, feel free to blame your 4 year old (though from the photos I'm fairly certain she is an angel).

But dust on a filter or a lens ALMOST never shows up in a photo. At least I have never seen it. The dust on the sensor will only show up when stopped down. Also, the dust removal mechanism in the Fuji may shake it loose so sometimes the dust spots move around from to time.
 

KillRamsey

Super Moderator
Jun 20, 2012
124
Hood River, OR
Kyle
It isn't the ND filter. Dang. Shooting the white ceiling above my desk, I went through f22 all the way in whole stops down to 2.8. Dark blemishes clearly visible at f22, fading down to f11, gone at f8 and below.

?!
 

john m flores

All-Pro
Aug 13, 2012
124
I struggled with college physics when they got to light (wave nature, particle nature, let's call the whole thing off!), but the idea of stacked rotating polarizers never struck me as a good one. You're not likely to get even transmission, but that does depend upon the light source.
 

Luckypenguin

Hall of Famer
Dec 24, 2010
123
Brisbane, Australia
Nic
Polarisers on ultra-wide angle lenses can cause problems because the change in polarisation as the angle to the sun changes is very noticeable.

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The larger smudges seem too big to be dust on the sensor, although the smaller dots may well be. Do you get the same effect using the 14mm lens without the variable ND filter attached?
 

KillRamsey

Super Moderator
Jun 20, 2012
124
Hood River, OR
Kyle
Regarding "do you get same effect without ND filter", the smudges DO still happen on the 14 when it is stopped way down. The banding thing, obviously not.

I wrote B&H to ask if I could send them a few sample images and ask for help. If this is just par for the course with the 14 because it's wide, then can I safely assume that a static 10 stop (for example) ND filter would work ok?
 

KillRamsey

Super Moderator
Jun 20, 2012
124
Hood River, OR
Kyle
Holding the ND filter in front of the 27 pancake, when I crank it to 8 stops dark, I can clearly see the same dark angled banding. As I rotate the filter around (not changing the darkness, just rotating the whole assembly) I can see the "X" rotating.
 
Jan 31, 2011
164
Newcastle, Australia
Sue
Using any kind of variable filter is fraught if your lens has a front element that rotates. I have a couple of ND filters, an ND8 and an ND400, and I wanted to get a graduated ND filter, too, but I've found that the graduated filter of Nik Color Efex Pro works just as well, in post, as it would on camera at the time, so I don't fret any more about having an area of a photograph slightly overexposed (usually happens to skies, when I am trying to get foregrounds)
 

KillRamsey

Super Moderator
Jun 20, 2012
124
Hood River, OR
Kyle
Research and a response from a B&H cust service rep confirms that "this just happens with all variable ND filters," pretty much.

Why
Do
They
Sell
Them

So now I'm going to have to return it for a static one, 8-10 stops I guess, to be able to do long exposure landscapes. Hopefully with some step-up rings I can also use it with other lenses.
 

Djarum

All-Pro
Jul 10, 2010
123
Huntsville, AL
Jason
This is typical from what I've read about various brands of variable ND filters. Most exhibit this issue. I've read about this issue using a circular polarizer stacked onto a linear polarizer as well. Same effect I believe.
 

NightBird

Regular
Apr 23, 2013
103
Sydney, Australia
Darren
I Just tried the a standard Hoya HD polarizer on my XF 14 and had a similar, though much less severe result. I remember on my Nikon 11-16 I used to have the same problems also. I just stopped using them for the most part on wide lenses. It does depend on the angle of light as well.

I've read that this is quite common and somewhat normal with wide angle lenses.
 

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