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SRB Photographic - Variable ND Filter - part 3 of 1 2 3 4

by Mike McNamee Published 01/12/2012

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The Maltese Cross is evident in 24mm, 28mm and 50mm Nikkor fixed lenses. It is not present in the 105mm but is replaced by a red spot on the middle of the image!

A Nikon D700 was set up with a Nikkor 24-85mm zoom using 200 ISO. This gave a baseline exposure (ie no filter) of 1/8s f8 and the residual error was just +1/3 of a stop (ie insignificant for practical purposes, the whole Macbeth Chart is probably not representative of a 50% grey card).

The addition of the Variable ND required an additional 2/3 of a stop exposure along with about 250K of colour temperature correction.


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Some of the time you will get away without any troubling artefacts. Here the shots are from a 28mm Nikkor used at about ND 5x. Apart from the uneven darkening of the sky towards the right-hand side. The 2.5s exposure (f16 200 ISO) has allowed the leaves on the tree to blur. The bottom right image has no filter attached to the lens - note the evenly rendered 'white' sky (and that the sun went behind a cloud!). The other images range from f2.8 to f16 and indicate that there is no variation (in this test) due to aperture.

The filter was then rotated and three exposures were made at nominally 3x, 6x and 10x ND values. No exposure measurement could be registered by the camera metering at the 10x setting and the exposure was determined by looking at the histograms of test shots.

We had heard criticisms of colour shifts using this class of filter but the data shows that with a minimum of colour correction in Raw you give very little away in terms of overall colour accuracy in the finished target. At the higher levels of ND setting, when the meter ceases to function, an extra stop or two of exposure represents a good starting point to make a test exposures. This is hardly point and shoot but this type of photography is usually a more considered affair in any case. Digital with the feedback of the histogram makes this sort of thing very straightforward in any case.

In round figures, then, a base exposure of 60s f8 allows for two minutes at f11, four minutes at f16 or eight minutes at f22 using 200ISO in daylight - good enough for 99% of situations.


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1st Published 01/12/2012
last update 21/07/2022 08:46:26

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