Using Neutral Density Gradient filters

Mt. Oberlin Alpenglow, Glacier National Park.  I used 2 ND grads, a 2-stop soft, and a 3-stop soft, to capture the enormous dynamic range of this image in-camera.
Mt. Oberlin Alpenglow, Glacier National Park. I used 2 ND grads, a 2-stop soft, and a 3-stop soft, to capture the enormous dynamic range of this image in-camera.

One of the great things about the advent of digital photography is that it has greatly reduced the number of filters I need to carry. Many of the functions we used to carry out with filters (warming/cooling, color filtering for B&W, soft-focus effects) are now much more easily and more accurately controlled in post-processing. But a few filters are still impossible for me to replace, particularly my polarizers and my set of neutral density gradient filters (ND grads).

ND grads were designed to address one of the fundamental challenges of photography, the challenge that light has too much dynamic range. We see the world with image sensors of seeing detail in a range  of 13-14 stops in the same scene, our cameras tend to top out (even if we nail our exposures perfectly, which we don’t always do) at a few usable stops fewer than that. This means that we often see scenes in the world where we can make out detail and color in the shadows and in the highlights, scenes that our cameras cannot capture entirely. Because we often have the situation where the highlights are on on side of an image (e.g., the sky) and the shadows are on the other (e.g., the land), ND grads are an attempt to address this by darkening the lighter part of the image to bring it closer in exposure to the darker part. They’re grey (neutral) on one side, clear on the other, and there’s usually some sort of transition zone between the transparent grey area and the clear area to possibly make the effect less overt.

(HDR imaging can sometimes be used as an alternative to ND grads–however, it will be much harder to get a good result from HDR imaging if you’ve got moving subjects in your images.)

Some manufacturers make both “soft” and “hard” ND grads. These terms describe whether that transition zone is broad and gentle (“soft”) or narrow and abrupt (“hard”). Certainly, in the same situation the “hard” grads will produce much more abrupt transitions than the “soft” grads. Yet,   just how ‘soft” the transition appears in the image is not only a function of the filter itself, but also the aperture, focal length and focus distance. With respect to focal length, the longer the focal length, the more gradual the effect of an ND grad will appear. As for the other parameters, if you think of the filter itself as an object you’re photographing, the more “out of focus” it is (wider aperture, focus farther from the camera), the softer the effect of the filter.

I work  primarily with two- and three-stop  filters. It’s rare that I need a one-stop filter; the scenes that could use just a little darker sky are easily adjusted later. For scenes with even greater contrast ranges I’ll sometimes use multiple filters, as I did in Mt. Oberlin Alpenglow.

Because you’ll want to adjust the placement and orientation of the transition when you shoot, I recommend the use of ::amazon(“B001RRSDJU”,  “rectangular-style filters”):: and ::amazon(“B0010841A6”, “filter holders”)::, avoid screw-in ND grads at all cost. Adjusting the placement of these filters is made more difficult by the fact that the effect varies with aperture, just looking through your viewfinder won’t show you the right effect unless you use your depth-of-field preview button, and using it (which I recommend) will make it difficult to see what you’re shooting. LiveView is an workable alternative on some cameras.

With practice and care, you’ll find that these filters can allow you to capture single images of scenes with enormous contrast, even with moving subjects. That unique ability is what earns these little gems a place in my gear bag.

This Post Has 10 Comments

  1. Very beautiful image Mr. Decker. I’ve always been worried about using a graduated ND on anything other then a flat horizon or something with a fairly clean division. I think I can see your dividing line but you did it so well. I would never have attempted this image like you did which is another example of the Lord showing me to reach beyond myself! You did really good on this one! Thanks also for pointing directly to the filters. I haven’t purchased mine because I keep coming up with reasons not to (HDR is one). But if you can create this image without HDR, it “adds” so much to the qaulity of the picture! God bless!

    Bill C.
    Albuquerque NM

  2. @Bill, @PeachTree: Thanks!

    And Bill, Yeah, the placement of the dividing lines is always a challenge. While it wasn’t necessary here at times I’ll try and do a little “cleanup” in post-processing. In that one pic, I think the two filters are actually in different positions, one soft filter coming down just into the mountains, another more along the bottom of the valley. Neither of them (I think) were horizontally aligned, either.

    (Another way to deal with images like this short of “real HDR” is what I call “poor man’s HDR”. Take the multiple exposures like you would for HDR, put them on separate layers after aligning them, and then simply hand-paint the layer mask in Photoshop. I find it easier to get realistic results this way than via the use of HDR software.)

    Thanks again!

  3. I have never been able to master the graduated ND, I have several, some said soft is to hard to see the line, so I bought Hard ND’s still no luck, never though of stacking them. I’ll give them another try, now that I got live live maybe I’ll be able to see what I’m doing.
    Awesome image, very inspiring so I’ll give the ND’s another go.

  4. Louis: With the softs, if you still have trouble seeing them using depth-of-field preview, I’ve seen folks get a sense of where the transition is by holding a business card or the like at the transition point. It’s still imperfect.

    Mostly I end up using soft filters–hards are really only appropriate when you have a very hard transition in the first place (ocean horizon, maybe), and even then it’s a trick to get something realistic looking. Err on the side of putting the transition on the darker and more uneven side of any transition.

    Hope that helps!

  5. I’m glad you mentioned the “poor man’s HDR” Joe – there’s actually nothing “poor” about it, it often yields much better results than HDR, and affords more control than using ND grads in the field. I stopped carrying ND grads in my bag years ago because it’s simple to achieve the same effects in Photoshop. You can use the Gradient Tool, by the way, rather than hand-painting the layer mask, although hand-painting allows you to make the “gradient” any shape you want – it doesn’t have to be a straight line.

  6. Mike: Absolutely–I do carry NDGs but use them much less often than I used to. And yeah, not just painting, but gradients, and I’ll often do blurring (global or selective) to clean up anything I’ve roughed into a mask by hand, covering the digital alternatives should probably be a follow-up article. Thanks!

  7. Joe: An absolute beginner question for you….when you say you used both a 2 stop soft and a 3 stop soft, how do you mean? Stacked over each other to make the equivelant of a 5 stop? or 2 stop on one are of the photo and the 3 stop on the other?

  8. Overlapping, so as to crate a softer (broader) 5-stop gradient.

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