Editor’s note: This is a guest Post by Ugo Cei. See his work right here.
In recent times I haven’t been making much use of filters in my photography. I would occasionally use a polarizer and that’s all. As a consequence, when faced with landscape scenes with a lot of contrast, like when the sky is bright, but the ground is in shade, I would normally resort to bracketing and then merging the resulting shots to HDR or doing some kind of blending.
Graduated Neutral Density (GND) Filters
When creating HDR photos, I always strive to produce natural looking results but, depending on the scene, my attempts are not always successful. Because of this, and because at this point in time I am trying to spend less time at the computer and to get more photos right in camera, I resolved to bring back from retirement my old Lee Filters rectangular, hard GND filter.
Doing so reminded me of why I haven’t been using it much at all. For one thing, a hard GND (Graduated Neutral Density) presents an abrupt transition between its clear and dark parts and this makes it only suitable for scenes where the horizon is flat. If you have mountains above its line, they will be too dark. If there are any objects, like trees, crossing the horizon’s line, the will be darker at the top. This negates all the benefits of using a GND filter.
Additionally, I find that precise placement of the filter so that it matches the skyline to be quite difficult at times, creating unnatural transitions between the ground and the sky.
Another reason why I haven’t been using this filter is that it’s plastic and prone to scratching. As a matter of fact, even though I’ve always handled it very carefully, it’s all scratched. I’m not sure the scratches would be visible in photos, but I know they affect image quality when shooting straight into the sun, something I tend to do frequently.
So I was looking for a replacement when a friend suggested that I try the new “medium” GND filters from NiSi. As the name says, a medium GND filter has a transition between the dark and light areas that is halfway between the abrupt one provided by hard GNDs and the very gradual one provided by soft GNDs. NiSi says it is recommended for images that feature buildings, mountains, and other small elements that protrude into the skyline.
So I ordered a 100x150mm medium GND filter with a 0.9 density (3 stops) and brought it with me on my most recent trip. I didn’t need a holder because this filter is the same size as my old Lee one, so I knew I could reuse the old system with the new filter.
How Good Is It Optically?
This is not a scientific test done in the lab, but I tried to measure some characteristics of the filter with as much accuracy as I could. I especially wanted to answer the following questions:
- Is the filter color-neutral or does it introduce undesirable color casts?
- Does placing the filter in front of a lens decrease its sharpness?
- Does the filter create flare or ghosting when shooting into strong light sources?
- How accurate is it?
- After having applied the proverbial two grains of salt, here are my conclusions.
I tested for the presence of color casts by photographing a white sheet of paper, with or without the filter. White balance was set based on the sheet itself under sunlight. I then measured the RGB values of the resulting images using the color picker in Adobe Lightroom in various parts of the images.
Discrepancies between the channels measured to less than 1%, so I can say with confidence that the NiSi filter is remarkably neutral and doesn’t introduce any color casts.
On the left: with the filter. On the right: without the filter.
I can’t see any degradation of image sharpness when the filter is mounted.
On the left: with the filter. On the right: without the filter. 200% enlargement. Shot on a Fujifilm X-T2 with the Fujinon XF 16-55mm F2.8 R LM WR lens.
I did this test by photographing a white sheet of paper with and without the filter, using the same settings (0.8s at f/5.6, ISO 200). The filter was positioned so that only its darkest portion covered the field of view.
I imported both files into Adobe Lightroom, increased exposure on the filtered image by 3.0 and compared RGB readings in the center of both. The image taken with the filter is slightly darker than the one without: RGB values were around 77% for the former and 81% for the latter.
While this is clearly not a very precise measurement, I would say that the density of the NiSi filter density is remarkably close to the 3 stops advertised.
On the left: with the filter. On the right: without the filter.
How Useful Is It?
I bought this filter because I thought it would be more useful than either a hard- or a soft-GND, on the average. Of course, no amount of gradation can be perfect for all situations, so it would arguably be best to have a hard-, a soft-, and a medium-GND in one’s bag. Maybe it would be even better to have filters with densities of 2, 3, and 4 stops to cover a wider range of lighting imbalances. Considering that this filter alone cost me about $150, getting 9 of them is out of the discussion, so I decided to go for a medium gradation and a medium density, knowing it wouldn’t always be a perfect match.
Here’s an example of a scene where one might want to use such a filter. First, a photo was taken without the use of any filters. In order to maintain enough detail in the shadow, the sky on the left had to be overexposed to the point of clipping the highlights.
The same scene, but now using the GND filter. The sky is darker and more colorful, with no clipping, while exposure on the ground is pretty much the same. There is no hard edge across the building on the right.
In this case, it would have been hard to obtain a similar effect in post-processing, for example using a graduated filter adjustment in Adobe Lightroom. Even when highlights can be recovered, I believe it is much better to get a photo right in camera, when possible.
When the range of light in the scene exceeds the camera’s dynamic range, a GND filter can make the difference between a photo bound for the trashcan and a perfectly exposed one.
Here’s the final image, after having applied some tonal adjustments in Adobe Lightroom.
Having had this NiSi Medium GND filter for a short time, it’s too early for me to draw conclusions about its usefulness in the long run. I can already see that it’s going to get more use than my old hard gradient filter, since I rarely get to shoot scenes with a clean horizon, but how much use it will actually get still remains to be seen. For sure, I am confident that it won’t degrade my photos in any way, so I can use it any time I feel like it makes my life easier.
Ugo Cei is a fine-art travel and landscape photographer from Italy. If you were to ask him what he does, he would say that he is an educator who helps photography enthusiasts sharpen their skills, so that they can take amazing pictures. He does this in various ways. First of all, by providing a wealth of free content on his website. He also leads photography tours and workshops to some cool destinations, including Oman, Venice, Milan, Cinque Terre, and Sardinia. He co-hosts and publishes a weekly podcast about travel photography, The Traveling Image Makers. Every week, they pick the brains of famous and not-so-famous travel photographers to learn what it means to travel for the love of photography and photograph for the love of travel.