amfoto1 Loc: San Jose, Calif. USA

That's a Variable ND filter, isn't it?

There is no avoiding those problems at stronger settings. You'll see it happen a lot. That's why I recommend NOT buying Variable ND for still photography. You'll probably also see color tints at times, which will be hard to get rid of.

The reason it happens is because Variable ND are in fact two polarizing filters, stacked one on top of the other. (Edit: No one is suggesting you buy two CPL and do this... what we are saying is that's what you've already got. Variable NDs actually are a pair of CPL, permanently stacked on on top of the other.))

You know how in certain situations a polarizing filter's effect is uneven? Well here you have it doubled and 90 degrees out of phase with each other.

There are "weak" Variable ND now being offered that are less likely to show that effect. Instead of covering 1 stop to 9 stop range, they cover a 1 stop to 5 stop, 3 stop to 7 stop, or 5 stop to 9 stop range.

But even that doesn't guarantee the problem will go away completely. There's no "practicing" or anything you can do, other than try different settings. "Higher quality" Variable ND aren't entirely free of the problem, either.

The best way to avoid the problem is to not use Variable ND.

Instead just get fixed, single strength ND filters.

For still photography I recommend a 6-stop (ND64) filter as the most widely useful. Add a 3-stop (ND8) filter and you have both a weaker option, but by stacking it with the 6 stop you can have a stronger one as well.

Since you already have a lot of exposure control with still photography you can get by with just one or two fixed strength ND filters.

Videographers have less exposure control so may need to do more fine tuning with ND. That means either needing to buy and haul around a stack of single strength ND, or one or two Variable ND.

Depending upon what type camera you're using, a strong ND can make focusing and composing difficult. A DSLR's optical viewfinder can get awfully dim. It may be possible to do "exposure simulation" in Live View on a DSLR or in the electronic viewfinder of a mirrorless camera. Otherwise, the filter may need to be removed temporarily. This is one time a Variable can be handy... because it can be turned to a weak setting for focusing and composing, then set to the stronger setting to take the shot.

An increasingly popular alternative is magnetic filters, which are easily installed and removed to help with composition and focusing.

rmalarz Loc: Tempe, Arizona

"The best way to avoid the problem is to not use Variable ND."

That's exactly what one of the optic engineers and B+W told me. He said it even applied to their product.
--Bob

delder Loc: Maryland

As previously noted,
ND and Variable Density are 2 ENTIRELY DIFFERENT types of filters.
ND will have a more or less linear response, while the Variable will be affected by all sorts of physics due to the 2 different polarizing filters involved, the angles they are set at and the available lighting.

wmurnahan Loc: Bloomington IN

Good catch, I didn't even think of a variable ND filter. Was scratching my head figuring out where a X would come from a ND filter

srg

That shot is definitely worth all the agida you experienced. Wonderful.

winhto Loc: Edmonds, Washington

Sorry, I meant SS8.

winhto Loc: Edmonds, Washington

So did I John. I thought my first was not good enough for maybe something was wrong so I bought a second one, just different brand 😁

winhto Loc: Edmonds, Washington

Thanks srg 😁

winhto Loc: Edmonds, Washington

😁😂🤣 to wm

winhto Loc: Edmonds, Washington

Yes it is amfo.

CHG_CANON Loc: the Windy City

Consider using <quote reply> for directed responses to specific prior posts.

CHG_CANON Loc: the Windy City

deleted / dup

Dr.Nikon Loc: Honolulu Hawaii

When I use a ND .., it’s always a Variable .., the shot is serenely perfect …!

winhto Loc: Edmonds, Washington

👍