Hard GND filters - they don't make a hard line in image?

I am evaluating getting a GND capable filter system (probably Lee).

The hard edge GND filters seem illogical to me. Almost never am I shooting something that has such a hard line between the light and dark. It just seems to me (having never used them) that a soft edge would be pretty much always what you would want.

Can someone school me on this? Perhaps give an example of a hard edge? If I apply a hard edge GND as post processing in lightroom, it pretty much never works in an acceptable way.

-K

Ocean Sunset/Sunrise = Hard Line

Hard edge real filters are completely different from in-computer.

Your program is applying the filter to a 2-D data plane. The Filter on the lens is affecting a 3-D light gathering system.

At extremely wide angles, with small apertures, you might get a hard line in your image, but even at 21mm and f11, the hard edged filters have a significant transition zone.

As you increase the focal length or open up the aperture, the lens not only sees a smaller part of the filter, but it is more out of focus due to the focal plane getting smaller and farther away. By 100mm and f4, I can barely even see the edge of my Hard GNDs.

This is why a good set of GNDs will include hard and soft, and reverse, in multiple strengths. Each scene and focal length and aperture will work best with a different combination.

If you are using a telephoto, you will probably want as hard and as strong as you can get, at wide angles, you might want a softer, or medium filter a bit less strong. Lots of variables.

Personally, I feel somewhat unprepared with only my soft 2-stop and 3-stop reverse (hard with a 1-stop fade going up). You may want more types.


Just dont rule out hard because a computer program doesn't make it look right haha.

I almost always use a hard grad, even when things are sticking up above the horizon line (naturally, depending on the situation). The hard grad makes it much easier to dodge and touch-up the offending items since its gradient is a bit more consistent than that of a soft grad. Best to take the "hard grad with flat horizon, soft grad when not" rule-of-thumb with a grain of salt, at least IMO.

Hard grads have their uses when needed.

1 stop hard GND.

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Ok. So if I'm just starting out, what 2 GND filters would you recommend? One hard and one soft? 0.6 ?

Can't go wrong with Galen Rowell's recommendations which are a 2 stop soft and 3 stop hard if you're only carrying 2; hard and soft in both 2 and 3 stops if you carry 4.

A nice benefit of the Lee 4x6 hard edge grads is that they're long enough to work as a regular ND filter since the shaded section is pretty big. Even at 17mm on a full frame camera, its surprising how little of the filter is needed.

^As Jon mentioned, I would also recommend both two/three stop GNDs in hard and soft.
Here's a sample using the three stop soft GND.