Review – URTH ND8-128 Variable Filter 

INTRODUCTION

As mentioned in our previous review of the  URTH ND2-400 Variable Filter, we have never really been big fans of using a Variable ND Filter in our photography. Mainly because we’d heard so much about the dreaded ‘X’ effect issue that these filters have. The URTH ND2-400 filter has the ‘X’ effect when used at the Maximum Setting but it is usable from 1 stop to about 5 stops reduction in light. Beyond the 5 stops, the corners are just too dark for our liking, although some may find it acceptable. As we needed a second Variable Filter, we decided to get the more expensive URTH ND8-128 Variable Plus filter (USD$99.00 / 77mm thread) which would reduce light by 3 to 7 stops.

We have great expectations for this filter, considering the usable range of the Urth Variable ND2-400 filter. Generally speaking, in most cases you will not need an ND2 (1 stop) or ND4 (2 stops) filter in the field. In fact, in some cases, a CPL filter can adequately be used to replace an ND2 filter. So, in our opinion, a variable filter starting at either ND4 (2 stops) or ND8 (3 stops) is perfect for most occasions. Therefore, our first impression is that the ND8-128 (3-7 stops) could be a very desirable range to work with.

It will be interesting to see whether it will become a permanent fixture in our camera bag. Continue reading to see our conclusion at the end of this post.

SO, WHAT IS A VARIABLE ND FILTER?

A Variable ND filter is a neutral density filter that allows you to manually adjust the density (strength) of the filter. Typically, you twist a ring on the outside of the filter, similar to a polarizing filter, and the filter shifts between low and high densities (often anywhere from 1 up to 10 stops of light depending on the brand).

WHY USE A VARIABLE ND FILTER

As Travel Photographers we tend to take a wide range of images and more recently during trips to Japan, Hong Kong, Macau and Shanghai, we have been taking a lot of street/urban-type images. We love to blur movement in our images, and this was not ideal at times using a bulky Square Filter Holder combined with the 6 or 10-stop filters, so on bright sunny days, many of our images had to be shot at a small aperture (f16-22) with low ISO settings to obtain the slow shutter speeds that we required. However, shooting at a small aperture can result in ‘Diffraction‘, which most photographers try to avoid (don’t worry about shooting at small apertures if your intended output is just social media). Ideally, we wanted to shoot at larger apertures (f2.8-f8) but with slower shutter speeds (see image below). The only alternative solution was to look at a Variable ND Filter where we would have complete control over the amount of light that would allow us to achieve the slow shutter speed we needed.

Please Note: We are NOT dedicated Landscape Photographers. For our tripod-mounted landscape images, we would generally NOT use a Variable ND Filter. Instead, we would use a Square Filter Holder and  URTH Square ND Filters.

As mentioned above, Variable ND Filters have had a reputation over the years for being quite expensive. However, over the last couple of years, we have been using the GOBE/URTH brand of filters and have found their filters to be of the highest quality while remaining reasonably priced. The URTH Variable ND8-128 Plus filter ranges in price from USD$75.00 for the 37mm lens thread up to USD$159.00 for the 95mm lens thread. The filter came in a round metal case slightly larger than the filter itself, much better than the flimsy plastic cases that some filter makers provide. It also included a URTH Cleaning Cloth, which was a nice addition. The filter is well-made and the rotating ring is smooth, although it is a little tight to rotate which, in our opinion, is a good thing as it restricts it from moving once set. The rotating ring is also quite narrow, so for those of you with ‘big fingers’, it may be a bit awkward; however, it is a necessary evil to avoid excessive vignetting in the corners of the frame. The filter is made with premium German B270 Schott optical glass with 20 layers of ultra-nano coating and is weather-sealed.

THE FILTER

The URTH Variable ND8-128 Plus filter can be rotated from ND8 (12.5% light transmittance), equivalent to 3 stops, to ND128 (0.781% light transmittance), equivalent to 7 stops. This is a fantastic range and will cover most of your long-exposure needs. The filter has ND8 and ND128 marked on the rim the separated by dots to indicate each stop of light reduction.

VIGNETTING

In our testing with the Gobe version of the filter we were sent for this review, we have found that it works well with wide-angle focal ranges such as 16mm-24mm. We tested it with our Sony FE 24-105 f/4 and Sony FE 16-35 f/4 lenses. Straight out of the camera, the filter causes vignetting on the 24-105mm lens, but this is immediately corrected once the lens profile is applied in post-processing. We used a 72mm-77mm step-up ring to use on the 16-35mm lens which caused some vignetting. Even without the step-up ring, there should be some vignetting, however, we are unable to test whether this is completely correctable on the 16-35mm lens in post-processing.

THE ‘X’ EFFECT

No matter what focal length you use we have found that the dreaded ‘X’ effect issue does not affect images when you use this filter.

COLOUR CAST

The filter will give you a colour cast. As you can see from the test images below the filter displays a slightly warmer colour cast than the shot without a filter. Personally, we don’t mind this. 

FILTER MARKINGS

There are no ‘stop’ markings on the filter so when using the filter you will need to have some sort of an idea of the shutter speed you want to attain for your image. Naturally, at the ND8 setting, it should be a 3-stop (or thereabouts) reduction in light but beyond that, you will have to watch your shutter speed if you want to calculate full-stop increments. Quite frankly, we would suggest you ignore the marks on the filter ring and instead rotate the ring until you obtain your desired shutter speed to capture the effect you want.

SHARPNESS

As is the case with most, if not all, Variable ND Filters there is a slight loss in sharpness when using this filter. As Variable ND filters are constructed from two circular polarising layers of glass that are placed in opposition to each other, a slight loss of sharpness can be expected.

Note: This is just a guide. You should always test your filter settings as they may change from copy to copy. The test below was taken using a Sony A7R III camera with a  Sony FE 24-105 f/4 lens at the 24mm focal range. These have only had the lens profile applied and have been straightened. Hover over the images for a magnified view.

TEST IMAGES

Above: La Perouse in Sydney, Australia
Sony A7R III + FE 24-105mm f/4 lens + No Filter
24mm – f/8 – 1/80 – ISO 100 –  WB Auto. Profile Correction added and straightened only

Above: Sony A7R III + FE 24-105mm f/4 lens + URTH ND8-128 filter.
Set to the ND8 (3stop) mark on the filter.
24mm – f/8 – 1/4 – ISO 100 –  WB Auto. Profile Correction added and straightened only.

Above: Sony A7R III + FE 24-105mm f/4 lens + URTH ND8-128 filter. Set to the 2nd mark on the filter.
24mm – f/8 – 0.4sec – ISO 100 –  WB Auto. Profile Correction added and straightened only.

Above: Sony A7R III + FE 24-105mm f/4 lens + URTH ND8-128 filter. Set to the 3rd mark on the filter.
24mm – f/8 – 0.6sec – ISO 100 –  WB Auto. Profile Correction added and straightened only.

Above: Sony A7R III + FE 24-105mm f/4 lens + URTH ND8-128 filter. Set to the 4th mark on the filter.
24mm – f/8 – 1.3sec – ISO 100 –  WB Auto. Profile Correction was added and straightened only.

Above: Sony A7R III + FE 24-105mm f/4 lens + URTH ND8-128 filter. Set to the ND128 mark on the filter.
24mm – f/8 – 1.6sec – ISO 100 –  WB Auto. Profile Correction was added and straightened only.

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CONCLUSION

,We found this filter easy to use. It gave us so much more control over our shutter speed when shooting at our ideal apertures. There is minimal loss of sharpness and only a slight colour cast. But most importantly, this filter does not have the dreaded X effect. The filter is ideal for wide-angle lenses, however, as mentioned, we can not vouch for the lens correction performance on lenses wider than 24mm. Undoubtedly, there will be some vignetting on wider lenses which should be correctable in-camera or in post-processing, but to what degree, we are not sure. You may also want to consider the URTH Variable ND2-32 Plus filter (1-5 stops). Based on its performance, this filter has found a permanent home in our camera bags and we look forward to many years of use. 

If you have any questions about this filter, please leave us a comment.

RATED: HIGHLY RECOMMENDED

PRICING

Other Gobe/Urth Filter Reviews

If you are interested in reading any of our other Gobe/Urth filter reviews click the links 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.