A dark ND filter is a necessity for long exposure times when the ambient light is very high. After reading various reviews and collecting feedback from photographer friends of mine, I bought a Hoya PRO ND 1000x filter. I could not get it on time for a recent trip that I had made but I still managed to use it for some test photographs.

As per the Hoya’s website – The ACCU-ND technology in the Hoya PROND filters yields a truly neutral color which is similar across all ND filters of the range. The PROND filters use Hoya’s exclusive clear optical glass that has a metallic ACCU-ND coating front and back to create the neutral density affect.

The PRO ND filter comes in a standard Hoya filter case which opens like a jewel box and the filter sits snugly on a pad of foam. The only indication of it being a new or a used filter is the pair of sealing stickers at the edges, which can be removed and pasted carefully if someone wants to, without any sign of the filter case being opened. How does it matter as long as the filter looks new and unused?

The ND filter itself is extremely dark to look at. The box states it as a 10 stop ND filter. That’s good amount of light reduction, for getting motion blurs with even wide seascapes or large rivers. The standard numbering for a 10 stop filter should be 1024 but Hoya seems to have rounded it of to 1000.  10 stops of reduction are equivalent to 3.0 ND density or decimal number notation. (Neutral Density Filters)

Testing the filter

For testing the filter in real world usage, I planned to use it on a Zeiss 25mm f/2 lens. The lens is one of the sharpest wideangle lenses available. Used with a decent camera body, the lens gives excellent image quality. This combination was a sure shot way to observe any drop in image quality in real world usage. Motion blurs are also prone to camera shake and drop in sharpness. I took along a sturdy Vanguard tripod.

(Barrage on river Ganges – Photographed using Apple iPhone 5s and then enhanced in Snapseed app. Resized in Affinity Photo. This was my location for testing the filter.)

After using it for a few shots, I noticed that the reduction is not exactly 10 stops. It is slightly less than 10 stops (which I guess is the reason why Hoya calls it 1000 instead of 1024). This negligible difference hardly matters. At the low shutter speeds at which I captured the photographs, the f-stops are not very accurate. God bless the creator of histograms. A quick preview takes the guess work away from using a ND filter. (Understanding Histograms) I recommend relying on histograms rather than f-stops or filter factors when using such dark filters. No need for exposure bracketing which used to be the standard with such filters, back in the film days.

(The smoothening effect of the long exposure motion blur worked well with the river. Nikon Df with Zeiss 25mm lens at  f/11 and a little less than a minute exposure time, with ISO set at 50. The Hoya PRO ND 1000 filter was placed after focusing the lens.)

The filter is so dark that it is impossible to focus or meter through it, as can be expected. The recommended method is to manually focus the lens without the filter and then mount the filter before capturing the image, making sure that the focus does not change. Camera mode should also be set to ‘M’ or Manual. For metering, take the reading without the filter and then count about 10 f-stops down so as to increase the exposure time. Mount the filter and then capture a few shots. Check the histograms on the preview screen and make adjustments accordingly.

(Another photograph of the river at almost the same settings using the Hoya PRO ND 1000)

I got some good photographs with this filter. Later when I analyzed the results on my computer, I could barely notice any fall in sharpness. In one of the photographs, I did notice some drop in sharpness around a high contrast element, but I consider it to be some freak result due to fault in my photography technique. There was no noticeable flare. There was mild shift in color balance, towards warmth but it could have gone undetected had I not captured some images without the filter. Again, not a big problem in digital era. Back in film days, we had to deal with something called as reciprocity failure. Compared to that, minor shifts in color are fine. In fact, Hoya PRO ND 1000 filter seems like the best ND filter in this range available presently in the market. The color shift is negligible compared to many of the other popular brands. The image sharpness is maintained. The photographs also had some areas with mild difference in overall hue. This was due to long exposure noise. Switching on the long exposure noise reduction helps.

This filter gets the maximum stars from me, and I can foresee that it will now be a constant companion on my upcoming trips. Hoya PRO ND 1000 filter is as good as it gets and is definitely worth the price it sells for.

Further Reading:
Creating Motion Blurs
Neutral Density Filters
Overflowing Stream