Saturday, July 23, 2011

Using graduated ND filters

click photos to enlarge
In the days of film photography I used a fairly wide selection of filters on my SLR camera lenses, and one or two on my rangefinder camera. I still have most of them, and several weeks ago I was looking at the collection, trying to decide which had a future and which I would be unlikely to ever use again.

I think its very doubtful that the red, yellow, orange and green filters that I used with black and white film will find a place in my future photography. The digital equivalent of these, applied to a colour image converted to monochrome in post-processing, seems to me to offer significant advantages over shooting in black and white with a filter on the lens. Nor too, I think, will the 49mm polarising filter be used again: my current lenses have much bigger filter sizes. I suppose, however, if I ever bought a compact system camera - M43, NX, NEX or somesuch, it might fit a lens. I also have a set of square filters of various kinds with a group of mounting filters, but once again these are of a size suitable for smaller diameter lenses. So, even though some of them, such as the neutral density filters, continue to have a very real purpose in these digital times, they are just too small for the lenses I currently use.

My attention had turned to filters because I was wanting to use a graduated neutral density filter to make better use of the sky in my images. It's true that with digital you can expose for the sky and then bring up the underexposed ground in post processing. But the fact is this takes time, effort and skill. Moreover, it's often the case that the dynamic range of the shot is too wide to do it completely successfully. The graduated neutral density filter tones down the brightness of the sky at the moment of capture and makes the details more as our eye sees them. It's especially useful, I find, on overcast days where the sky is white (but figured) and the ground dark and without obvious shadows. It is also useful when the camera is pointed anywhere near to the sun. Occasionally, however, this kind of filter does make too much of the sky's details and it can look a touch apocalyptic!

The upshot of all this is that a while ago I bought a 72mm mounting ring, filter holder and a square ND8 graduated neutral density filter. Fortunately the 24-105mm and the 17-40mm lens both have 72 mm filter threads, so the two lenses I own that are most suitable for this kind of filter can be accommodated by the single setup.

The photographs above were all taken on a rather overcast day using the filter. They show the late C15 (and later) Mannington Hall, a moated house in Norfolk. I may have been able to achieve the balance of the first image without the filter, and perhaps the second one too, but the third shot really benefited from it, acquiring a mood that would have been difficult to reproduce with a normal exposure and post-processing.

photographs and text (c) T. Boughen

Photo 1
Mode: Aperture Priority
Focal Length: 28mm
F No: f7.1
Shutter Speed: 1/125
ISO: 100
Exposure Compensation:  0 EV
Image Stabilisation: On
Filter: Graduated ND8