billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

I only use a 10 stop ND filter. Why? Because the exposure is easy to calculate. I get the initial exposure correct using a shutter speed of 1/30 sec. Then I know when I put my 10 stop ND filter on, the correct exposure will be 30 seconds. Simple.
Remember to use a tripod and cover your eyepiece, and turn off your auto focus.

bleirer

Is it that the filters are not truly neutral? Or an artifact of long exposure in General? Both?

jerryc41 Loc: Catskill Mts of NY

ND filters are very versatile. One thing I find puzzling is that there are, I think, three different ways to classify ND filters, and it can get confusing. Good links below.

Very good article - https://www.youtube.com/watch?v=ZpNtAXbaNr0

Comparisons -
https://improvephotography.com/40253/nd-filters-30-filters-reviewed-compared/
http://nofilmschool.com/2016/02/5-filters-go-head-head-neutral-density-shootout
http://www.the-digital-picture.com/Reviews/10-Stop-Neutral-Density-Filter.aspx

More info -
https://www.bhphotovideo.com/explora/photography/hands-on-review/a-guide-to-neutral-density-filters
https://www.lightstalking.com/quick-guide-to-understanding-nd-filters/
http://friedmanarchives.blogspot.com/2018/02/neutral-density-filters-vs.html
https://www.howtogeek.com/325803/how-neutral-density-filters-work-and-how-to-use-them-for-better-photography/
https://improvephotography.com/40253/nd-filters-30-filters-reviewed-compared/
http://www.alexwisephotography.net/blog/2009/07/23/neutral-density-reference-chart/
http://digital-photography-school.com/beginners-guide-buying-filters/
http://digital-photography-school.com/step-by-step-guide-to-long-exposure-photography/
http://www.the-digital-picture.com/Reviews/10-Stop-Neutral-Density-Filter.aspx
http://www.cambridgeincolour.com/tutorials/neutral-density-filters.htm
http://www.alexwisephotography.net/blog/2009/07/23/neutral-density-reference-chart/
https://www.youtube.com/watch?v=ZpNtAXbaNr0
https://www.ephotozine.com/article/how-an-nd-filter-can-remove-crowds-from-busy-shots--27054

JayRay Loc: Missouri

Where was the location of your beautiful waterfall photograph?

tcthome Loc: NJ

It has been a while but, I think this will cover it.

https://www.youtube.com/watch?v=MEIwYbZHOb0&list=PLOD1rrjm5sQAIAuOetLgtaxp7K30QtMNO&index=113&t=2s

amfoto1 Loc: San Jose, Calif. USA

Variable ND filters are essentially two polarizers, stacked. If you are familiar with the "uneven affect" that can occur with polarizers, it's even worse with Variable ND. A big "X" will appear in many of your images, which is virtually impossible to correct well in post-processing.

If you only want to make still shots with longer exposures, that's pretty simple and one or two standard ND filters of fixed strength will work much better than a Variable ND filter (which almost always cost more, too).

With a fixed strength ND there is no risk of the uneven exposure problems. This type of filter is simply dyed a neutral gray.

For really long exposures, you may need a 9 or 10 stop ND filter. For more moderate length, around 6 stop ND is generally fine. Or for use in lower light conditions (deep in the woods, early or late in the day), you may need a weaker 3 stop ND.

I recommend a 6 stop as the best "all around" choice. Or, also get a 3 stop, then you can stack the two if you need stronger, or have the alternative of a weaker ND if needed. But some landscape shooters prefer one 9 or 10 stop. It's up to you. If you buy top quality, stacking two should be fine unless you're using the filter on an ultrawide lens where that would cause vignetting in the corners.

For still photography one or two ND filters is usually all you need. Variable ND are more likely to be needed for videography, where there is less control over exposure in other ways and finer control with the filter may be needed. Ideally a videographer would also use fixed strength ND too, for best video quality. However that might mean buying and carrying around a stack of filters. A Variable ND is simply more practical for video.

But for still photography one or two fixed strength ND can usually handle all your needs. With still photography, you just need to "shift" your exposure range fairly strongly, and can then fine tune it with other controls (ISO, aperture and shutter speed).

One way that variable ND might be helpful is that they can quickly be set to a minimum while composing and focusing, then turned to the strength you want to make the actual exposure. It can be a problem with a strong filter installed to see to compose or to focus. A lot depends upon the other gear you're using and the light conditions you're dealing with. For example, mirrorless cameras that can preview exposure, brightening up what you see on their electronic viewfinders to help you compose, as well as aiding manual focusing. Some mirrorless camera AF systems are also able to work in considerably lower light conditions than the typical DSLR, too, so AF might be usable with them, while AF fails when there's a strong ND on a DLSR's lens.

There are other possible solutions for this "problem", besides Variable ND: You can temporarily remove the filter from the lens while composing and focusing, only installing it when ready to make the exposure. Or, Live View on the rear LCD of a DSLR (or a mirrorless, for that matter) might assist with composing and, if necessary, manual focusing while the filter is installed. If using a DSLR, check if it can do "exposure simulation" in Live View. Also check if it has manual focus assist features, such as "focus peaking" (which many mirrorless have, but not all DSLRs do... However, in some cases focus peaking can be added, such as with the Magic Lantern app that's available to use with some Canon DSLRs).

Besides allowing for longer exposures that create deliberate motion blur effects in images, another use of ND filters is to allow especially large lens apertures to be used for shallow Depth of Field effects in brighter lighting conditions (I'm getting one to use on an f/1.1 lens I've got, which I have to stop down to a middle aperture in brighter daylight conditions... Without an ND filter, setting it's lowest ISO and using my camera's fastest shutter speed isn't sufficient to allow larger apertures to be used, which is sort of the point of buying a "fast" lens).

bleirer

Interesting. He explains how to fix it, which is good, doesn't cover why it happens, though.

Kozan Loc: Trenton Tennessee

You only need one filter-- a 10 stop ND filter. As some have said, different brands produce a color shift. And price has nothing to do with it. Matt Ganger did a comparison of about 15 different brands. You can view that on YouTube. Very eye opening. From what I remember, the Breakthrough X4 came out the best.

Also, Lee filters has an APP out that automatically converts the shutter speed from No filter to 6, 10, and 15 stop filter. It is free in the Play Store or App store. I think it's called the Lee Stopper app.

A 15 stop filter is very good for capturing scenes with no people in it. I once photographed a scene that had many cars coming through and a 15 minute shot eliminated all the cars. It's also great for historic buildings where you want to eliminate people.

But again, the 10-stop filter is probably the most useful.

Kozan

JimRPhoto Loc: Raleigh NC

Hello Spike. I have eventually figured out that the most useful time with digital photography (as opposed to the film days) is to use a graduated ND. I use the Cokin brand. There is a holder that screws into the filter threads on your lens, and the holder is essentially to hold a square filter. On particularly bright days, taking photos in the Blue Ridge Mountains, for example, where the contrast would have you lose all the detail in the trees and foliage, I have found really good results with the graduated ND. You need to use a tripod for this, and align the graduated transition from clear to grey along the horizon to darken the sky. The holder permits you to slide the filter up and down. One response you had suggests that the ND adds a color tint. I have not found that, but note that there are graduated ND filters that use blue instead of grey. I have not used them. (In the film days, I would use a round ND if I had a fast film, say 800 film, and it was a bright day. Don’t use the round ones now - but those who like the look of flowing water use them to extend the shutter open time.). I’m sure you will get other useful tips here. JimR.

DWU2 Loc: Phoenix Arizona area

You can read about it here: https://fstoppers.com/bestfiltertest

via the lens Loc: Northern California, near Yosemite NP

10-stop for slowing water down, Breakthrough filters is the one I have.

bleirer

Thanks, so it is the filters not being totally neutral, not the long exposure itself. Another reason to shoot raw.

photoman43

I agree. I just purchased a NISI starting kit with 100mm wide ND and GND filters and a 82mm circular polarizer that fits the holder that comes with the kit. My most used ND filter today is a 6 stop.

Check out the nisi v6 system and the various starter kits. Look at videos to see how any such system is used before you buy anything.

rbhallock Loc: Western Massachusetts

Folks -

Breakthrough technologies seems to have the ND filters with the least color cast. Some filters by others tend to pass a little bit too much red compared to blue, or in other cases, too much blue compared to red. The effects are small in most cases, but they are present and will be visible, especially in critical situations. The breakthrough technologies web site shows you a nice graphic that will make this clear.

Bob

Rmccully

I use Breakthough filters - I use the 6 stop and 10 stop. I also use their Polarizer. They provide the best color capture with no color cast. I use the magnetic filters, which I love -- So day to put on and remove.