Thanks to cameraland.nl I got the opportunity to test the Rodenstock Vario ND filter, a variable neutral density filter. Last year I got my hands on the LCW Fader ND mkII for a test (click here to see the results). Personally I was not very impressed by the LCW Fader ND, not even by the mkII. My main concern was the ‘cross’ (crucifix or ‘X’) the would show while using a wide angle lens. It appeared on my Canon EF 24-70mm f/2.8 USM so I didn’t even bother to test the Canon 16-35mm f/2.8 USM II. (See on the example of the cross issue on this page.) So I was hoping the Rodenstock Vario ND will perform better.
The first difference that I noticed was that the product description of the Rodenstock Vario ND was pretty clear on the ‘known’ issues with wide angle lenses. They even marked the filter with ‘max’ which is just next to the +5 marker. Anything beyond this max marker is not guaranteed to give good results. And they were right. If you ignore their warning you will get unexpected results as you will see in my tests. I didn’t really experience any issues with color shifts, so that is way better compared tot the LCW Fader ND mkII. With the lather I experienced color shifts on several occasions.
With the filter from Rodenstock I decided to give it al full test. I tried it on almost every piece of glass that I own. This caused a few problems due to the fact that I got the 82mm version of the Rodenstock Vario ND for my test and most of my lenses have the 77mm thread. So I needed an adapter ring. Normally this wouldn’t be a problem but this time I experienced vignetting on my Canon 24-70mm f/2.8 USM when set to 24mm. And I do not know if the vignetting is caused by the filter itself or by the use of the adapter ring. The 82mm showed some vignetting on my Canon 16-35mm f/2.8 USM II when set to 16mm at f/2.8. I didn’t really experience vignetting when set at f/22.
As you can see on the example below, I took 9 shots (‘no filter’, min, +1,5, +2, +3, +4, +5, max, beyond max) for each lens/aperture/zoom-level combination. (ie. for my 24-70mm I shot on 24mm and 70mm, at f/2.8 and f/22 – so that adds up to 4 x 9 shots for this lens)
impressed by the Rodenstock Vario ND, and especially not due to the high(er) price range of the Rodenstock Vario ND MC. I still experience the cruciform issue (the big black ‘X’) and that occurred in most cases right after the ‘max setting. While with the LCW Fader ND mkII in some cases I able to use a higher setting before I encountered the ‘X’. The filter is officially sold as a variable ND with a range from 1-9 stops, (i.e. 2,8x-400x) In none of the occurrences during my test I was able to use the filter beyond the max setting which is in most cases is equal to +6 stops. So you will not be able to use +7 till +9 stops. If anyone has other (better) results I am more then happy to hear from you. So that makes me wonder why they even bother to sell it as a 1-9 stops range filter. Has to be a commercial decision I guess.
The main difference that I experienced was the lack of color shifts in the +1 till +5 stops range. In some occasions I experience loss in light at the +5 stop setting (ie. darker then expected results) so I think that my light meter got fooled by the use of two polarisation filters. I also experience loss of contrast, but that is of lesser concern to me due tot the fact that this is something which is easy to correct when using RAW.
Overall I think the Rodenstock Vario ND is a better option compared to the LCW. This due to the fact that in the +1 till +5 stops range you get better, clearer, and sharper results.
So if you need a variable ND filter the Rodenstock Vario ND MC is a very good option. But if you need more than +5 stops for neutral density or grey filtering – buy a fixed filter and avoid the variable ND’s all together.
Click on the images below to see the test results for each lens combination.