teeford

Do they work satisfactorily, or should I buy a set of fixed filters?

Nikonian72 Loc: Chico CA

Following.

Pablo8 Loc: Nottingham UK.

No, and yes.

Leicaflex Loc: Cymru

I have had no experience with adjustable ND filters.
I use only fixed ones and it is not a problem for me.

Haydon

f8lee Loc: New Mexico

Adjustable ND filters work by having two circular polarizing filters that are set to turn against each other - since a perfect polarizing filter blocks out all light in one Direction, one stacked on the other and oriented at a 90° difference should ideally block all light - thus the notion of a variable ND.

I have used one with great success for both film cameras and certain DSLRs (Nikon D200, D600) but when I tried it on my Fuji X-T1 I got the artifacts sometimes known as the "Maltese cross". This is where a darkened X appears on the image-I presume due to some kind of destructive interference between the foils used in the polarizing filter and the spacing of the photo sites on the imaging chip.

On DSLRs, they are quite convenient in that you don't have to remove the filter to frame and focus a shot and then replace it to make the exposure (assuming, of course, you don't have the artifacts). I found on the Fuji, though, that the EVF presents a fully visible view even when a 9 stop filter is attached to the lens very convenient, and a little freaky), so there was no need for the adjustable ND.

speters Loc: Grangeville/Idaho

I have both and I do not have any issues with either one!

Cdouthitt Loc: Traverse City, MI

Fixed.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

The do sometimes. Not very well with wide angle and ultra wide lenses. Color casts, loss of contrast, different color cast at max and min effect, and with wider lenses, vignetting and the "cross of death"

http://photorec.tv/2015/08/variable-nd-filter-vs-non-variable-nd/

If you need a variable (can't imagine why), you should probably get the $40 Bower filter - it is relatively neutral, and has good optical quality. Save your $$ and get fixed. An 8 stop and a 4 stop should be able to give you what you need.

rook2c4 Loc: Philadelphia, PA USA

If you expect to use ND filter regularly, invest in a set. If you don't think you'll be using ND filter much beyond once or twice a year, and you're on a limited budget, the variable filter will do just fine.

Shoeless_Photographer Loc: Lexington

Hmmm...I have more than one CP filter. Are you saying I could just stack a couple of those and get the same effect as a variable ND filter?

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

I feel fixed are more accurate unless you experiment and put marks on the side of the adjustable. I have a 10 stop filter I use most of the time and I also have a 1.5, 3 and 6 stop ND filters. I have experimented and know exactly the exposure needed for each and in combo with each other. I have owned a variable but do not use it anymore. Mine are Tiffen filters.

CO

There's an excellent 52-page guide to long exposure photography that you can download. The author describes all of the different ND filters. There's a photo in the guide that shows the Maltese cross effect when a variable ND is used with a wide angle lens. I'll post the link to it below. You have a join their newsletter to download it. I think I just unsubscribed to the newsletter later. I have a Hoya Pro-1 3-stop and a 4-stop ND filter that I use. They seem to be all that I need.
http://breakthrough.photography/essential-reference-guide-long-exposure-photography-download

jims203 Loc: Connecticut

I have a Singhray variable I have used on several Nikon bodies and lens. It always performs well. Esp useful on waterfalls.

jerryc41 Loc: Catskill Mts of NY

Considering the price, I've avoided them. I have a moderate and a more extreme ND, and it fits all my lenses, some with step-up rings.

http://photography.tutsplus.com/articles/an-in-depth-comparison-of-two-variable-neutral-density-filters--photo-8983