Vivitar Variable ND Test

DailyFilmFix

Here's a test I did today with the Vivitar NDX variable filter. I have been in post on my latest doc, "Three Days at Foster," and I've been working overtime on color correction. I used this particular filter on my Zuiko 45mm because the filter was for 37mm thread. I knew there were concerns about color cast and loss of sharpness, but a lot of what I shot was lovely anyway. The rest, I'm fixing.

So, for this test, which is probably not well done, I set up my GH1 with the reliability hack and set it to smooth with everything -2. I manually white balanced on the white door with each test after I set exposure. I pulled focus using a loupe.

To my eye, the one with the filter on it and the extra LED light does look, perhaps, a little less sharp. When I sharpened, it became a little more clear that there may be a slight loss of sharpness. But you guys look at it and tell me if my eyes need to be reset.

I ran three cameras on my doc (two GH1s and an HMC150) and was able to find an angle every time that worked. But I did not properly pay attention to color on some shots and tried to dial it in. After this test, I'm going to manually do it moving forward. Actually, I did manually balance with my video camera (the HMC150) on each interview, which did make a difference.

My main question is: now that Light Craft has a 37mm variable ND available at Adorama, based on this test, how much better would it be?

Finally, I realize that the casting and focus issues would become more pronounced as I cranked the ND down (darker), however, mine was set in the middle of the scale on the side of the filter, which I thought would be good for this test.

DailyFilmFix

I need to run this test again. I think that the non-ND shot is actually at F4. I wrote it down wrong when I shot the footage. This would account for the shallow DOF in the ND shot. But the tip of the door handle focus is fairly sharp, I think.

Aria

@DailyFilmFix, I think the Vivitar NDX footage looks great! I think especially so with the light sharpening. I would have no reservations in using the NDX based on what i'm seeing. It's not a very exhaustive test, but from what you've shown it looks good to me. I wonder who is making the Vivitar NDX for them. It looks like Tiffen ND to me.

Perhaps you should do a test with some text print so you can compare sharpness a bit better.

CRFilms

Appreciate the test, but yeah, a new one would be nice. You really need to shoot it outdoors to really test it out. I bought a $40 vari-ND of ebay and it's ultimately unusable. In order to get 50 shutter under F5 in most daylight situations. I had to stop it down all the way and it was starting to get that "X" pattern when I stopped it down. Unusable. I'm too cheap and broke to spend the real cash to buy one that won't do that. Especially if it costs $300+.

vicharris

Try running this test on a longer lens. When you reach 50mm, these cheaper NDs start to fall apart quick. I have the LCW and a Genus. Both are unusable past 50mm IMO but maybe this one is different. Seems the color shift is not bad too.

vicharris

@CRFilms Try the Genus Eclipse. It can run with the big boys in terms of quality, sharpness and color shift. They run $160

labalbi

I am still learning about ND filters. But wouldnt be a good idea to use a big nd filter with a step-up ring ? So you can use it with other lenses as well ? Or the step-up ring would cause some trouble like vignetting ? thanks

DailyFilmFix

Doing the test with an image filled with text on a white background would be a good idea. I'm currently in post on my doc feature, "Three Days at Foster." And I shot most of the film using these filters. We did something like 43 interviews. It is my second feature doc shooting it myself. This shoot was much better than my last experience on a couple of Panasonic video cameras.

My image is pretty darned good, but I factored in the color cast. Focus can really be a problem but that is not always the filter's fault. I got a couple Vfinders for my two cameras (GH1s) about half-way through my shoot and cut down on focus errors. Focus can't be fixed, but color can be managed.

thepalalias

@labalbi Step-up rings are actually often good for avoiding vignetting.

For instance, when I start stacking contrast filters on a 77mm thread lens, they rapidly vignette. But when I stack the same onto on a smaller thread lens with a step-up ring I can stack more without vignetting.

Rambo

CRFilms, one way to avoid the huge stop down on the VariND and the "X" is to use a fixed ND behind the VariND. I quite often use an ND2 or ND4 with the VariND mounted on front, I guess you could say it acts as a preset.

It's another piece of glass but have no adverse affects I can see used with the Vari.

DailyFilmFix

Shot some broll today with just natural light, of course, and did not use the ND filters. I think that I may have been using more light than I really needed for interviews. For example, once I three point lit the subject, I then had to use the ND to open the aperture and get the shallow DOF effect that I wanted.

The thought has now occurred to me, after shooting hundreds of interviews this way, that maybe, just maybe I can get away with less light on my subjects. My first doc feature back in 2005, I shot with one shop light occasionally and my images were usually pretty decent.

On Friday, I'm going to shoot two more interviews for my next doc (we're building on our Kickstarter success with the first one), and I'm not taking my softboxes, just my two LEDs and a reflector with a stand. We'll see how it goes.

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