Review – URTH 100mm Square ND Filter 

INTRODUCTION

We’ve been using URTH products for a few years and exclusively use their circular screw-in filters on all our lenses. We have tested and reviewed their UV, ND2-400 Variable, ND8-128 Variable, and Night filters (to read the reviews see the list at the bottom of this post). In our opinion, they have hit the mark for quality, price, and results. You also have to admire a company that not only provides quality products but also channels a portion of its profits to plant trees in some of the most deforested regions of the world. What more could you ask for?

Riding on the success of their circular screw-in filters they have decided to enter the very competitive market of square filters. Square Filters are primarily used on tripod-mounted cameras by landscape photographers, which would have to be the most popular photography genre amongst professionals and enthusiasts alike. They are commonly used on ultra-wide-angle (<24mm) and wide-angle lenses (24-35mm) but naturally can be used on any focal length. So there is a very large market for this type of filter.

Please Note: We will always recommend a product based on its quality and price. If a $132.00 filter provides the same results, if not better than a $240.00 filter we would naturally recommend the cheaper filter regardless of our affiliations with the more expensive brand.  Please read our disclaimer at the bottom of this post.

So, why should you buy the URTH 100mm Square ND Filter? We’ll get to that a little bit further down.

SO, WHAT IS AN ND FILTER?

An ND filter is a neutral density filter that reduces the amount of light that reaches the film/sensor. It is produced in three forms –

• Circular ND Filter – fixed strength filters in a variety of lens thread diameters eg, ND8 (fixed 3-stop)
• Circular Variable ND Filter – variable strength filters with a rotating ring that will change the strength of the filter in a variety of lens thread diameters eg. ND2-400 (variable 1-8.65 stops)
• Square ND Filters – fixed strength filters in a variety of sizes which are dependent on the lens. The most common is the 100 x 100mm filter. A square filter holder is also required.

The square ND filter comes in a variety of fixed strengths varying anywhere between 1 stop to 20 stops. Unlike a circular screw-in ND filter, a Square ND filter can also be used with a Graduated ND filter and CPL filter if using a filter holder without any significant vignetting.

WHY USE AN ND FILTER?

There are several reasons why you would use an ND Filter.

• If you are shooting in the middle of the day and there is a lot of ambient light you may want to use the filter to achieve a slower shutter speed while still attaining the aperture that you desire. To achieve the slow shutter speed without the filter may require you to use a small aperture such as f/16 or f/22 and this is not ideal as it may result in lens diffraction (slight loss of sharpness).
• To obtain long exposures for creative purposes such as smoothing out ripples/waves in water, blurring moving clouds, removing moving people from your shots etc.
• If shooting video you want to shoot with a shutter speed of close to 1/50th sec (25fps) or 1/60th sec (30fps) however, to acquire the desired aperture in different lighting conditions you will need to use an ND filter. For example, if you wanted to choose an aperture of f/2.8 in high ambient light the shutter speed would be too great. In this case, an ND filter would enable you to obtain the shutter speed required. Generally, a Circular Variable ND filter may be more practical when shooting video as it can be manually adjusted rather than installing a different strength square filter.

URTH 100mm & 75mm SQUARE ND FILTERS

A Landscape Photographer will spend a great deal on buying filters and will mainly stick with one system. These days, however, please keep in mind that except for a few extra features, most 100mm Filter Holders will accommodate any brand of 100mm filter. A 100mm filter holder will accommodate any brand of 100 x 100mm ND Filter or 100mm x 150mm Graduated ND Filter.  Some of these include Lee, NiSi, Formatt-Hitech, Kase, Haida, K&F, and Athabasca, just to mention a few. Square ND Filters are generally not cheap considering you will also need to purchase a filter holder as well. Prices for a 100mm Square ND Filter range from USD$70.00 up to USD$200.00.

Naturally, we cannot test every filter for this review but we can compare the URTH 100mm Square ND Filter – 6 stop (USD$129.00 against our NiSi 100mm Square ND Filter – 6 stop – USD$160.00). Note: You can also purchase the NiSi Filter in the Explorer Range for USD$139.00, however, we do not have this particular filter for comparison.

The URTH Square ND Filters can be bought in the following strengths for both 100mm & 75mm (now discontinued) filter holders. The URTH branded products are Plus which is their highest quality.

The Plus+ range features 20 layers of nano-coating providing a more consistent transmission curve for truer light reduction, easier cleaning and better protection against water, oil and scratches.

THE FILTERS

The filters arrived in a 16.5cm x 16.5cm x 2.5cm (6.5″ x 6.5″x 1″) recyclable cardboard box. The filter is presented in an attractive-looking Kraftex pouch. The pouch opening is magnetic and, therefore, a breeze to open and close. The filter has a snug fit in the case and is also protected by a protective sleeve with a tab on the top making it easy to pull out of the pouch. A URTH Cleaning Cloth is also included in the box (you can never have too many of these!). Every purchase funds tree planting in areas affected by severe deforestation — revitalising ecosystems and empowering local communities.

The filters are manufactured with premium German Schott B270 optical glass and coated with 20 layers of nano-coating for extra sharpness and durability. URTH also offers a Lifetime Warranty on the filters. 

The filter fits perfectly into our NiSi V5 Filter holder and we would assume this would be the case with all holders as they tend to be standardised for all 100mm filters. The first thing you will notice in comparison to the NiSi version of the filter is the lack of a rubber gasket which is applied to the rear of the filter to reduce any chance of a light leak affecting your long exposures.

Would the lack of this rubber gasket be an issue with our long exposures using our NiSi Filter Holder? Read on to find out.

UPDATE

In mid-2021, URTH launched its 100mm & 75mm filter holders  (75mm now discontinued) with a built-in rubber gasket. This is a great feature as the gaskets are prone to eventually detaching themselves from our NiSi Filters. If you are NOT using the URTH Filter Holder, you may consider purchasing some gaskets from NiSi and using them on the URTH ND filters, especially if you love to take fairly long exposures. If you are using the URTH Filter Holder with another brand of square ND filter you may have to remove the rubber gasket from the back of the filter if one is attached as it may be a very tight fit. In addition to the filter holder, they released a range of 100mm Graduated ND filters, a Reverse Graduated ND Filter, a Night Filter, and a Centre Graduated ND Filter.

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EXPOSURE TEST

We tested the filter on our Sony A7Riii mirrorless camera with a  Sony FE 16-35 f/4 lens with our original NiSi V5 Filter Holder (now discontinued and replaced with the V6 and subsequently the V7 Filter Holder).

The Urth and NiSi filters both achieved a 6-stop reduction in light.

We used the Urth Square ND64 filter with an exposure of 13sec and there were no light leaks. See the sunset image below. Therefore, the lack of a rubber gasket at the rear of the Urth filter did not affect the exposure. We have not seen any light leaks on images up to 30-sec but we suggest that you test the filter for longer exposures to see whether you need to attach a rubber gasket to the filter.

Above: View over the Mamanuca Islands from Denarau Island in Fiji
Sony A7Riii + FE 16-35mm f/4 lens + Urth Square 100mm ND64 (6 Stop) ND Filter.
19mm – f/11 – 13.0 sec – ISO 100

COLOUR CAST

We also compared the White Balance settings between AWB (Auto White Balance) and Daylight (5,500K). When set to AWB, both filters looked similar to the shot without a filter attached. When changed to Daylight, the exposure with the NiSi Filter had a slight magenta cast and the URTH filter went in the opposite direction and showed a green cast. Both are easily corrected in editing.

Note: This is just a guide. You should always test your filter as it may change from copy to copy.

TEST IMAGES

Below are the test images. These were taken purely for testing purposes. As mentioned above, we used a Sony A7Riii mirrorless camera with a Sony FE 16-35 f4 lens mounted on a tripod. The shots were taken as close together as possible. Hover over the images for a closer look.

TEST IMAGE RESULTS

We will be performing more tests with the filter and will update this post accordingly as the results above have raised some questions.

Our initial tests have shown that both the NiSi 6 stop and Urth 6 stop BOTH suffer from a slight loss of sharpness compared to the shot without a filter attached. But surprisingly, we have found the Urth filter to be slightly sharper than the NiSi filter!!! However, we have found that the Urth filter does suffer from edge darkness but this could be the result of the lack of a gasket on the filter and causing a light leak. Naturally, if you are using a square filter without the gasket with the Urth Filter Holder then you should not have any light leaks as the filter holder has a rubber gasket.

PRICING

Urth charges a flat price depending on the size of the filter rather than the density.

CONCLUSION

All 100mm x 100mm square ND filters are created equal when it comes to ease of use. However, what separates these types of filters is obviously the results and the price. At this point in time, until more conclusive testing can be done, URTH has, in our opinion, produced a winner with their 100mm Square ND filters. 

If you are interested in checking out some of our other GOBE/URTH Filter reviews, see below-

Disclaimer:  This review is totally unbiased. As Professional Photographers we would never recommend the use of any product unless we have used the product ourselves. We always strive to give you our honest opinion in order to help you make the best choice. We did receive the product with compliments of URTH but were not paid for this review. We may also receive commissions on other links in this post.