Sunday, April 10, 2011
Long exposures with a Hitech 4-stop ND
These days many people look to the latest cameras to capture sharp hand held images in low light using very high ISO settings for the fastest shutter speeds. A fast shutter speed freezes motion but there are also advantages to working at the other end of the spectrum - ultra slow shutter speeds. Slow shutter speeds can blur motion and create many desired special effects from motion like moving cars, people, clouds, water....
Experienced landscape photographers know that the photography is not just a technique to record your surroundings. Good composition and light, along with special effects like long shutter speeds can separate your work for others. Long exposures on a windy day can soften clouds; in streams it changes the texture of water in rapids or can capture beautiful leaf swirls in circulating pools of water; on beaches is can create an ethereal look when waves crash against the shore, and for waterfalls it lets you capture a silky look. Long exposures are done by using one or more methods like dialing down ISO to a very low setting, stopping down (unless you desire selective focus), and using a ND or neutral density filter. A CPL or circular polarizing filter, which is IMO the single most valuable filter to own, has the ability to act as a 1 - 1.5 stop ND filter. Screw on filters like a 3-stop ND filter are great but sometimes when the light is strong, and/or you want very long shutter speeds, 3-stops is just not enough. The next move is a denser filter like a 6-stop screw-on, or a very expensive Singh-Ray vari-ND, or using something like a flat 4-stop ND filter from Hitech.
I strongly prefer the flat design of 100x100mm 4-stop Hitech ND, which I have been using for about 2 years. The problem with the 6-stop screw on is that it can get too dark to easily compose or focus, especially in low light with a f/5.6 lens. Also screwing on and off can be a bit of a pain and time consuming. The nifty alternative is something like the SR vari-ND - which I also owned and used for about a year before before settling on a square 4-stop Hitech. The reason I did not like the SR is 1) it does not meter correctly due to the physics of the design so one must use manual mode and take a test shot or two to determine the proper exposure settings for set filters settings - if you are experienced and work quickly and instinctively as I do this can be real drag, 2) it is useless for the widest angle work since it will vignette - that means that you must own two sets of filters to cover all possible focal lengths. A flat filter held over anything has zero vignetting, 3) it is easy to over dial in the density which results in a weird cross pattern from the dual polarizers which is not obvious in the viewfinder. 4) they are very expensive and therefore tricky to justify especially since you will likely need still another filter to handle the wide end, and 5) it is slower to use than simply holding a square filter over the lens or mounted filter.
I shoot a significant amount of waterfalls each year plus many streams and shores... I often use a CPL filter to manage glare when working with water which also helps with about a stop or so of density. If longer exposures are desired but not glare handling I just screw on my six year old 3-stop ND. When I need more the just hold my 4-stop over the lens or filters since there is no fear of vignetting and I can quickly see and shoot both fast and slow shutter speeds without screwing around, (pun intended) or metering things. If I desire very long shutter speeds like 20 - 60 seconds and plan on doing a lot of that type of work I simply can use my Hitech with a Cokin Z-holder so I don’t have to keep holding yet can quickly remove and replace. All my grad-ND’s are the larger Z-size since I prefer to handhold and bigger is easier to hold. This works great when doing things like capturing the pattern of swirling leaves where I want as long an exposure as possible, like a minute or more and using Bulb mode where one needs at least one free hand to end the exposure. However, more often than not I simply use it hand held.
To see what I am doing I first compose (possibly with a CPL or another 3-stop ND screwed on which is plenty of light to see what I am doing). Once I compose I use the AF button to lock in the focus without locking in the exposure - which is what happens when you depress the shutter halfway. I then place the filter over the lens, expose and shoot. This gives me plenty of flexibility to quickly shoot something both fast and slow as well as have my viewfinder bright enough to see. Very simple, very fast, and very affordable, my 4-stop Hitech ND resides in my Tamrac filter belt pack along with my other round filter filters so it is always at my fingertips. At about $70 this filter is nicely priced and will help you produce some very nice captures impossible without it. A few weeks ago as winter came to an end I hiked to Kaaterskill Falls in the Catskills on a bright sunny day. Using my CPL filter, ISO 100, and f/13, the water was still moving too fast to get a silky look so I just reached down and grabbed my 4-stop and held it over my CPL and voila, I was able to get my desire speed of 1/10 sec in bright light and a silky waterfall. I own 10 filters, 5 grad-ND, 2-CPL’s (different sizes), 2 ND’s, and a clear filter for foul weather condition. With those I can do just about anything and they are always at my side. I highly recommend this design filter over the alternatives.