Variable or Fixed ND Filter?

Techy Guy

Techy Guy

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Wanting to buy a couple of ND filters with high-ish factors (already got a couple of low value ones) and I see a lot of ads for variable ones at seemingly reasonable prices. Has anyone compared variable with fixed ND filters? How do they stack up image quality wise? Certainly the convenience is appealing. Any other considerations?

Thanks.
 
Avoid the variable density ones if you want to use a widish-angle lens at higher densities.
 
Variable ND for video, fixed for stills.
 
Bristolian said:
I'd be interested to hear the reason behind that statement.
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It may be related to their different use with video, basically as a fade-to-black device. I think that's where they originally came from. Personally, I wish they'd stayed there - even the mega-expensive ones are hopeless for stills with wide-angles IMHO.
 
Bristolian said:
I'd be interested to hear the reason behind that statement.
Click to expand...

I'm primarily a film maker and a photographer second and I'd agree with that. Its mainly to do with the speed at which you can change from say, half a stop of density to 2 stops of density. When you're filming in lots of different lighting situations on a run-and-gun basis you don't have time to change filters and having a variable really helps. In general with photography you have a little more time to swap around filters and can use the much higher quality fixed filters. I also hardly ever find myself shooting really wide with video, but often shoot wide when I'm taking photographs of landscapes (which in my experience is the time when I'd most use filters for photography).

Of course there are some videographers who have the luxury of time to use fixed filters and some photographers who like the convenience of the variables but I have found that the above statement tends to ring true.
 
HoppyUK said:
It may be related to their different use with video, basically as a fade-to-black device. I think that's where they originally came from. Personally, I wish they'd stayed there - even the mega-expensive ones are hopeless for stills with wide-angles IMHO.
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Hoppy, thanks for the response. Is the wide angle problem due to vignetting or poor quality of the filter causing IQ issues?
 
Bristolian said:
Hoppy, thanks for the response. Is the wide angle problem due to vignetting or poor quality of the filter causing IQ issues?
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More the inherent poor quality.....they're just 2 polarising filters you adjust against each other. This leads to you having a big dark cross, particularly in the sky with wide angles.
 
boyfalldown said:
More the inherent poor quality.....they're just 2 polarising filters you adjust against each other. This leads to you having a big dark cross, particularly in the sky with wide angles.
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Ah, that explains things, thank you.

It's always good to know why things are how they are ... good or bad :-)
 
Bristolian said:
Hoppy, thanks for the response. Is the wide angle problem due to vignetting or poor quality of the filter causing IQ issues?
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Nothing to do with quality. As Hoppy says, even the stupidly expensive high-quality ones will suffer the dreaded X-pattern problem. With wide angle lenses these VNDs will produce a dark X-pattern at high densities. With UWA lenses you can see the pattern start (dark corners) at quite low densities. It doesn't matter what you're shooting (sky or not) and it has nothing to do with vignettting.
 
I like my variable ND, but I don't use it wider than 24mm because it won't fit on my 14-24mm.
Soon I hope to add a 16-35mm so I can use filters @ UWA's and then maybe my opinion will change.
 
I'm interested in these beasts too. The Tiffen 85mm appears to be the best. The reviews for it are awesome within certain constrains i.e. not too wide (28mm min) not too dark (est 80% full range).
They are also quite expensive.
I'm sure the engineers would love that you call them just 2 polarising filters :)
 
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