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03-05-2011, 04:13 PM   #1
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Genus Variable Neutral Density Filter

The Genus seems to be an attempt at a poor man's Singh Ray. Depending on the site you find the listing, it claims adjustable up to 8-stops. The downfall is, there is no clicks, and there is no hard stop. There is a "guide" printed on the side of the filter.

Here's my results to a "controlled" test. My lights are cheap, I didn't use a tripod, and I'm using a 50mm lens for a "product" shot, so obviously take these results with a grain of salt.

These shots should've been roughly the same exposure, although they don't look like it. First shot is bare lens, 2 150w/s monolights at 1/8 power. Second is with the Genus, same in camera settings, but the Genus dialed in to 3-stops, and the lights at full power..

I fired the rim light so that it should create flare. I faced it more towards the camera than it should be. It seems that the flare shows much more green, as opposed to the bluish flare the bare Nikon coating creates. There is also a fare amount of white flare on the opposite side of the light source. There is ghosting right above the subject in both frames, and I verified it's not dust by looking at other photos before and after (would be a big chunk of dust).

Anyway, like I said, not something that is definitive, but it's a little info for those curious.





03-18-2011, 09:17 PM   #2
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I checked the filter out on eBay (Genus GNDF-72 - 72mm ND (Neutral Density) Fader Filter). It seems like a good concept, but isn't this just two polarizing filters (linear) that are crossed to reduce light? Can you do a test to see if you are getting the polarization effect when the filter is at its brightest?
04-10-2011, 02:46 PM   #3
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Sorry for the delayed response. Finally got some good sun to try it out. Didn't get any polarizing effect on the sky with these.







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04-11-2011, 07:35 PM   #4
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I think you may be getting polarizing effect. The first shot shows the front windshield more clear than the side. If you rotate the filter (at a preset density level) do the reflections shift (from side window to windshield)? Make certain you are not facing south when you shoot the glass. There is less polarizing effect when facing toward the sun (facing south in the north, facing north in the southern hemisphere).

04-11-2011, 08:35 PM   #5
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The windshield reflections didn't change from shot to shot that I noticed.
04-12-2011, 03:43 AM   #6
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Polarizing vs non polarizing variable ND filters

QuoteOriginally posted by BigDave Quote
I think you may be getting polarizing effect. The first shot shows the front windshield more clear than the side. If you rotate the filter (at a preset density level) do the reflections shift (from side window to windshield)? Make certain you are not facing south when you shoot the glass. There is less polarizing effect when facing toward the sun (facing south in the north, facing north in the southern hemisphere).
There are two ways to make a variable ND filter: one that gives a polarizing effect (like a single polarizing filter) and one that does not have a polarizing effect.

(1) Reverse a CPL on a CPL... [camera}[CPL}{CPL] .....a variable ND with no polarizing effect.
(2) Put a linear PL on a CPL....[camera}[CPL}[LPL}........a variable ND with polarizing effect.

Note: in case (1) a reversing filter adapter can be used to reverse mount the stacked CPL. In case (2) no adapter is needed - just screw the LPL onto the CPL.

This is because a CPL is actually a combination of a Linear Polarizer followed by a de-polarizer.

The LPL version is a little more versatile as it can be used to selectively reduce glare while also doing its ND job.
04-12-2011, 06:37 AM   #7
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Interesting. That makes sense. Thanks for the info!
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