As many reader of this blog will know, I often use a filter of one type or another. In actual fact my STC Hybrid CPL filter is an almost permanent fixture on my lenses.
Having woken early one morning to see a glorious sunrise over our local lake, I decided it was time to take some early morning photographs. Herein lies a problem (apart from getting up very early!), that is one of controlling the extreme brightness on the horizon. With standard landscapes a regular neutral graduated filter can be used to darken the the sky, but not so with a sunrise or sunset for that matter. Hence the need for something a little different – a reverse graduated filter.
How do the two filters differ? A normal graduated filter starts dark at the top and gradually gets lighter, ie. clear at approximately the mid point of the filter. A reverse graduated filter starts light and gets progressively darker towards the mid point, fades back slightly then become clear.
I managed to obtain a Hitech 0.6 (2 Stop) Neutral Density Reverse Graduated filter at a very competitive price. The Hitech filter like most neutral density graduated filters comes in a range of strengths – 0.3 ( 1 stop), 0.6 ( 2 stop) and 0.9 ( 3 stop).
Some information to note. Firstly the Hitech filter is made of CR39 resin and resin filters have never been a favourite of mine, but more about that later. Secondly the filter is 25mm shorter than my other Z series filters, it being 125mm in length as opposed to the usual 150mm length of others, but not a massive problem. Thirdly the graduation at the centre where the filter is at its darkest is fairly short, when used care is needed in lining the filter up with the horizon.
Best practice is not to stop your lens down to minimum aperture this tends to accentuate the sharp graduation of the filter in the centre, extreme wide angle lenses can also create a similar issue.
Hitech Reverse Graduated filter in use.
For the tests I used a Nikon D800 with Cosina 19-35mm and a Nikkor 24-85mm lenses fitted with a Zomei Z series filter holder modified to one slot only enabling the graduated filter to be kept as close to the lens as possible.
For comparison purposes also tested were conventional 84.5mm.com 0.9 graduated nd filter and Zomei 0.9 graduated nd filter.
The filter fits perfectly into the filter holder due to chamfered corners and it is very easy to line up the horizon in the viewfinder of the camera. The 84.5 filter does not fit so easily because it has square cut corners and appears to be slightly thicker. The Zomei filter fits into the holder well, having rounded corners to help it slide into position.
I usually make an initial light reading without the filter in place, fit the filter make a test exposure and make any adjustment needed to obtain a good exposure.
All exposures were made with white balance set to Daylight, files saved as NEF and the resultant images processed in Adobe Camera Raw.
For a resin filter, the Hitech filter is fairly neutral. This may sound odd considering that it is after all a Neutral Density filter. However, in practice not all neutral density filters are truly neutral. I also tested conventional neutral density filters by 84.5mm and Zomei to make a comparison. The 84.5mm filter is CR39 resin filter, whilst the Zomei filter is glass.
Both the Hitech and the Zomei filters are a close match with a neutral colour balance, the 84.5mm filter displays a magenta cast. None of the filters impact sharpness of the image.
Without filter
With Hitech Reverse Graduated filter
Sample images
Would I recommend the Hitech Reverse Graduated filter?
Simple answer, yes. Just take care when lining up in the viewfinder and look after the filter, being made of CR39 resin the filter can get scratched if treated roughly. Treat it well and you will get many years of service from it.