(EDIT: Over at f-stop forum Mark Soon has posted some findings with the Singhray that shows no artefacts. We have had some conversations as to why this could be, and we can’t seem to find out. I just recieved a new singhray yesterday, and I will try the tests again. Still my point remains: I would always recommend buying non-variable ND’s)
A little warning for my fellow photographers today. I like to shoot high speed prime lenses. That should no longer be a secret to the people who follow this blog. Ever since I started going “collectors heaven” with the old 50 mm lenses I have been needing ND filters in all shapes and sizes. And trust me on this
DON’T BUY VARIABLE ND FILTERS!
They will mess up your gorgeous bokeh, and specular highlights!
What a variable ND filter really is, is two pieces of polarising glass. One linear, one circular. You twist the filter to offset the polarisation. Polarized at a 90 degree angle, the filter lets in zero light. at 0 degrees it lets in 100% light. (Basic high school physics :-P)
What this sadly does is introduce artefacts into your out of focus areas. And before you start saying that this is only true on cheap filter brands… trust me…it’s not! I’ve tried variable ND’s from the following companies, and ALL with no exception show this issue!
B+W, Hoya, Hama, Heliopan, and Singh Ray. I returned them all!
They all show the exact same issue. The shots below were taken using the Hoya NDx8 and the Variable Hama NDx2-400. Both fitted on the Fujinon XF 56mm f/1.2. Again, this is to show the artefacts. As stated above this is the same for all 5 of the above brands. The Hama is the cheapest, and also the far worst of the bunch. Low contrast, grey dull colours and artefacts. It costs twice that of the normal Hoya NDx8 filter which I now use on ALL my lenses. Best value for money in ND filters as far as I’ve learned.
A couple of shots using the two most expensive Vari ND filters I’ve tried. Both with the same specular highlight artefacts.
So there you have it. A little word of advice from a dude who has tried a bucketload of variable filters. Only to return home to Normal single set ND filters.
Sofie says: Laters! 😀