One area most people don’t often experiment with is the purposeful use of long exposure times during the day. Night shots, streaking lights and star trails, are common and typically fairly easy compared to their daytime counterparts. For one thing, there’s so much light! Stopping down apertures and lowering ISOs only goes so far. The best most cameras can muster during the day is 1/10th of a second, maybe. To start adding dramatic effects to day time shots, neutral density filters can be employed.
A neutral density (ND) filter is akin to putting sunglasses on your camera, except that these sunglasses are neutral in color (although not all ND filters are made the same and some can cause a color cast). The filters are typically graded by how many stops of light they block out, such as 1 stop, 4 stops or even 9 stops. Beyond filters that are set at a particular density, variable neutral density (VND) filters can offer a wide range of effects. But not without some give and take.
I was lent a Singh-Ray Vari-N-Duo filter to find some of these limits and like most products, it has its pros and cons. This filter is listed to range from 2 2/3 stops to 8 stops in density.
First, the filter comes in two sizes; regular and slim. Regular is 17mm thick and Thin is 14mm. That little bit of thickness can make a large difference in full frame cameras and wide angle lenses, which I will cover in a moment. The filters are only available for 77mm barrels, which can be a limiting factor for some (although filter thread reducers are available to make a 77mm fit on a 62mm lens, for instance). It comes in a nice leather pouch for safe keeping.
Second, this particular filter was built with a landscape photographer in mind. The filter has two rings that rotate. The outer most ring seen in the photo above (click to enlarge) is used to set the amount of density desired; from Minimum to Maximum. The bottom ring also rotates free of the upper ring and controls a circular polarizer, negating the need to add on a second filter (which would constantly need adjusting every time a bit of density was adjusted).
The stop range allows for a range of blur adjustment. For instance, in these photos below, the first was taken without the filter, the second was with the filter set to minimum and the third was shot with the filter on the third full mark, just before maximum. The aperture and ISO were kept the same (f/13 and 100) for all the shots. The actual shutter speeds were listed as: No filter = .6 seconds, Minimum ND = 1 second and 3rd stop = 8 seconds. It is important to note that adjustments needed to be made in Lightroom after the images were taken, resulting in exposure adjustments of 1 stop, 1.35 stops and 1.5 stops, respectively. This is mainly due to trial and error in adjusting to the filter early in the process. Shot with Canon 7D and EF 10mm-22mm lens set to 17mm.
The advantage here is the ability to give more or less blur to the water, depending on your personal preferences. While the waterfall itself does not change drastically (the brightness of which is being aided by a gradient filter in Lightroom), the water in the foreground does feel different from shot to shot. Having this ability to adjust shutter speeds via the filter can be a useful tool in changing the nuance of a bright photo.
Incorporating the polarizing filter into (and behind) the VND filter allows for easy engagement, or lack there of, in any situation. For those unfamiliar with the effects of a polarizing filter, these two shots straight from the camera which should help show a difference. Both shots were taken at 50mm, ISO 100, f/18 and 1/13 second in broad daylight with a Canon 7D and 28-300mm L lens.
The first photo is without polarization and the second photo is with.
The amount of density can be fine tuned. While each mark on the filter does not correspond to an exact amount of stops (for instance, the first mark is not 1 stop darker and the second is not 2, etc…) the filter has a way of smoothly transitioning until the last set of marks before Maximum. This allows better adjustments down low where subtle difference can make a difference. Because of the means of manufacture, once at the third mark and before Maximum, there is a large swing from about five to eight stops difference.
These really are the biggest advantages of using a VND filter with a polarizer. The ability to blur movement in broad or partial day light can be a boon to creative photographers. And the ability to control the amount of blur, while possibly keeping the aperture wide open, can lead to some interesting shots. Here are some other examples.
ISO 100, f/29, 8 seconds with Polarizer engaged
ISO 100, f/13, 3.2 seconds
ISO 100, f/13, 1/4 second
ISO 100, f/13, 6 seconds
While the filter does allow for some interesting effects, it has its downside.
Price would be the biggest downside for many. The Singh-Ray Vari-N-Duo costs $390 (regular) or $440 (thin) retail. As that price is above the cost of a lot of readers’ primary lenses, it can be a tough pill to swallow and should be considered when shopping for such a filter.
Vignetting is another disadvantage. On a 16mm lens mounted to a full frame sensor camera, even the thin version will cause unwanted vignetting as the physical size of the filter can be seen in the corners of an image. This is clearly stated on Singh-Ray’s site (and was reemphasized to me by the PR rep). If you go too wide, you will encounter this effect. I could see the edge of the filter using a crop sensored Canon 7D when at 10mm (16mm equivalent). Because of the number of cameras and sizes of sensors and variety of lenses is so large, they do not give a concrete “At this focal length you will see problems”, but instead suggest zooming in a bit or changing composition.
Adjustment for those with larger hands can be a bit of an issue with the thin mount. My hands are average, as far as I know, and I was able to make adjustments without much problem. It is best to use two hands while adjusting the polarizing filter which will require a tripod most of the time. Granted, this filter is often used with a tripod, but sometimes it can be used to achieve a wider aperture in daylight.
Metering is also fuddled when the filter is on. Going by what my camera suggested for ‘proper’ metering often left images too dark. I found I had to make a chart showing how much I should compensate at different marks on the filter. But this didn’t hold true in every case. What I’m trying to say, is there is a learning curve to using the filter and you will need to take it slow when first employing it. With practice, it becomes easier.
Focusing is also difficult when the filter is stopped all the way down. Manual focus must often be used when darker settings are employed.
Only available for in 77mm diameter.
The Singh-Ray Vari-N-Duo is a fun filter to use and, when given specific application, can yield some shots most can not achieve without it. My time testing the filter was too short as I would have liked to get into more varied situations (it also would have been helpful if it was more sunny in Seattle this year!). Right now the price tag has me holding back from pulling the trigger on a purchase. Yet with trips to Nepal, Bhutan, India and Peru this fall I am itching to snag one, knowing it will surely help me bring back lively photos.