Chris Conti sent us this nice report he did on Variable ND filters and said we could share some of it with you (you'll have to read the whole report for all the details). He does select a winner between the two and there are some additional photos and thoughts on his post.
Battle of the VariNDs: What’s the Best Variable ND?
The most convenient way to use ND filters on DSLRs is the “VariND,” or variable ND filter, whose filtration can be adjusted with a simple twist of the filter ring. The problem with variable NDs though is that up until now they’ve usually been quite soft and tend to degrade image quality.
The two new variable ND filters that have come out recently that I had heard good things about were the Genustech Eclipse and the Tiffen Variable ND. Take a look at the video below for my intro to my testing.
If you’re interested in doing tests like this yourself, you can download the full-resolution test chart that I used here (it’s also handy for testing focus, adjusting autofocus microadjust, etc!).
I originally planned to stop both lenses down to f/11 for the tests to make sure that I eliminated as much softness coming from the lens as possible, so that I could really isolate softness being introduced by the filters. After conducting all the tests at f/11 though and inspecting the RAW files on my editing machine, I have to say I was completely blown away with the results: I couldn’t see almost ANY softness introduced by EITHER filter even at maximum filtration strength!
Even though the lens aperture shouldn’t matter in terms of the filter sharpness, I decided at that point that since I would likely be using these filters at wide apertures, I might as well test them at wide apertures. So then I opened the lenses up to f/2.8 and ran through all the test shots again. Again, the results were astonishing. Take a look at the 1:1 crops of the center of the resolution charts
So Were the Two Filters Equal? NO.
Even though both filters were amazingly sharp (gone are the days of soft VariNDs! Hooray!), they were NOT equals. The Tiffen Variable ND was the clear winner. Here’s why:
The difference between the Genus and the Tiffen was that the Genus started displaying the cross pattern above substantially earlier in its filtration range (in other words, had less usable range) than the Tiffen. Compared to the Genus, the Tiffen had an extra stop or two of usable range before it too started showing the cross pattern. It is a subjective judgement how much cross-pattern darkening is acceptable before the image becomes unusable, but using the same lighting and camera settings, it was clear that the Tiffen had substantially more range (I’d estimate about two stops) before it started exhibiting the same level of the pattern above as the Genus.
To learn more about the Best Variable ND in this test, visit Battle of the VariNDs
(cover photo credit: snap from the video)