By Jack Graham
Editor’s note: Many thanks to longtime Singh-Ray shooter and friend Jack Graham for contributing this article. Putting this post together helped us make a pleasant discovery, a beautiful and free online photography magazine we were not aware of – Extraordinary Vision Magazine. More details at the end of this post.
Long exposure photography has become very popular, with many popular websites and magazines featuring long exposure photography.
So what constitutes a long exposure?
Most DSLR cameras available today allow us to automatically set our shutter speed up to 30 seconds. However, to me a long exposure is just that: longer than I can render a subject in sharp focus.
This could be anywhere between 1⁄2 second up to a few hours, depending on the effect I want to create.
There are several situations in which long exposure can be applied.
We can leave our shutter open long enough for a car or bicycle to drive by and create an interesting blurred effect.
Long exposure photography can also be used in night-time photography to capture stars trails.
Another application of long exposure is light painting of an otherwise very dark scene. This involves directing a light source over a subject to add light and ambience.
Often we need to experiment with the amount of light applied to a subject as to not over-illuminate our subject.
Finally, my most often used application of long exposure is to capture moving clouds and water. Such an exposure often produces a mysterious, dreamy effect that may even seem surreal. Conveying a sense of the passing of time, such images present a departure from normalcy both from an artistic sense, as well as a viewing experience.
In the following narrative, I’m going to focus our discussion of long exposure photography to capturing dynamic clouds and water in landscape photography.
Long Exposure Equipment
First, you will need a good quality DSLR. As long exposures can introduce significant noise, the better your camera’s sensor, the better your images will appear. Now while you will not see noise (often called “hot-pixels”) on your LCD, it will be visible when viewing your images on your monitor. Your camera also needs to posses a “bulb” setting. The bulb setting allows you to keep the shutter open for as long as needed, allowing you to create some quality long exposures.
To trigger your camera and keep the shutter open for the required length of time, you will need either a remote shutter release cable or a wireless shutter release. There are many such releases on the market, some made by the camera manufactures and some aftermarket. If you plan on doing serious long exposure photography, my advice is to invest in a release with a built-in timer that you can set for the require exposure time for each individual image. Not only is such a release more accurate, it’s also a great deal easier than trying to look at your watch in darkness.
Next, you will need a good quality tripod and tripod head. While a tripod can help produce sharp images under normal shooting condition, it is critical when shooting long exposures. As wind, camera shake etc. are all magnified the longer your shutter remains open, the sturdier your tripod, the better your results will be.
As always, I recommend never extending your center column. If you do, you now have an unstable monopod. I sometimes see folks hanging camera bags from their tripod to try to anchor the tripod. A breeze might move this “anchor” thus making the tripod vibrate. Placing a beanbag on your camera will produce better results.
Finally you’ll need some filters to slow your shutter speed. These are commonly known as neutral density filters and they work by reducing the amount of light passing through them and falling on your sensor, and in turn allowing your shutter to remain open longer. These filters are rated in “stops” with each “stop” reducing the amount of light reaching the sensor by a factor of two.
For example, a 3-stop ND filter, (often referred to as a ND8) reduces the light by a factor of 8 (2x2x2=8). A 4 stop ND (or ND16) reduces the light by a factor of 16 (2x2x2x2-=16) and so on. When using a 10 stop ND filter, the light is reduced by a factor of 1024 (2x2x2x2x2x2x2x2x2x2=1024). This translates to the shutter being open for 1024 times longer than without the filter. If 100% of the light is transmitted with no filter on the lens, a 10-stop only transmits .19% of the light!
Many filter manufactures produce ND filters, of which I have tried most. From experience, I can tell you that all are not created equal. Such filters are not easily produced. They must be made of high quality photographic glass, not resin.
The good quality filters take some time to produce. Unless a manufacturer has an assembly line each filter is almost hand made. Quality manufactures try to eliminate color shift as much as possible. Some do. Most don’t. This process is quite extensive. High quality filters are also quite expensive, but considering the manufacturing process, they are really priced very fair.
Personally, I use two neutral density filters: the Singh-Ray 10-stop Mor-Slo solid ND filter and the Singh-Ray Vari-ND variable ND filter. Singh-Ray also produces 5-, 15- and 20-stop Mor-Slo filters. The 10-stop Mor-Slo is a screw-in available from Singh-Ray in many thread sizes, as well as in square and rectangular sizes. The Vari-ND is also a screw-in filter and allows you to vary the density from 2-8 stops. I also stack the two of them together, to get 12-18 stops of density (Note: to stack the Mor-Slo with Vari-ND, at least one has to be a standard mount with front threads – two thin-mount filters will not stack).
Long Exposure Technique
Mindful that different applications of long exposure photography require different techniques, for this essay we will confine our discussion of technique to landscape photography.
Like any other composition, composing your image, choosing your subject matter and assessing the light is critically important. Essentially, you are capturing the same image without the long exposure effect, but adding this effect to create the desired result.
Assuming you have chosen a good subject, with good light and one that has some moving water, clouds, and or other elements, let’s now discuss how I go about creating long exposures.
After setting up my tripod and camera I go through all the things I do for conventional photography. I then check the light and properly meter the subject without using any filters. Having a filter on prior to focusing will not allow you to see a thing. It’s just too dark due to the filter’s denseness. After metering my composition, here is my process.
1) I compose the image.
2) I determine my desired aperture and ISO.
3) I focus the image in the proper manner (if you autofocus without the filter switch to manual).
4) I determine the shutter speed based on my chosen ISO and aperture without the filter on.
5) I carefully screw in my filter of choice, either the 10 stop Mor-Slo or the Vari ND.
6) I double-check to make sure the screen that covers my viewfinder is closed. This insures proper metering and prevents light from entering the camera while the shutter is open. This is very important.
7) I now set my shutter speed on “bulb,” allowing my shutter release cable or remote timer to control the shutter speed.
8) I determine how long I need my shutter to be open based on the shutter speed determined without the filter. As this math can get quite complicated, you can either refer to a timetable such as the one I created on the next page, or you can use a free app such as Longtime Exposures.
NOTE: If your shutter speed is longer or shorter than desired, you can change the shutter speed simply by increasing or decreasing the ISO. But remember, digital noise increases with higher ISO’s as well as longer exposures!
9) I set my remote cable release to the desired time based on the shutter speed with no filter attached.
10) Assuming your light conditions haven’t change…. take the shot.
Timing your exposures
There are several variables you need to consider when making long exposures.
1) When making long exposures you’ll need to slow down even more than normal to make sure your settings are correct. Creating a concept for an image when making long exposures is very important. With time, you’ll learn to visualize the final outcome.
2) After you make the image do not use your LCD to evaluate anything other than your histogram.
3) Experiment! Change your ISO to make the shutter longer or shorter. Only when you review your results on your monitor do you choose the effect you like.
4) I always recommend shooting RAW files.
One Last Thought
In closing, I’d like to state that this essay is not an advertisement. It is simply my endorsement. I have experimented with filters from other manufactures. I have found without question the Singh-Ray filters to be of the highest quality without any measurable color shift. Color shift is the biggest problem in filters, especially ND filters. There is no easy cheap way to make a good quality ND. As such, I highly recommend Singh Ray filters.
To illustrate the variance in quality, I recently took these two images. The first was made using the Singh-Ray 10-stop Mor-Slo filter, the other with their main competitor in a similar price range. The results speak for themselves. There is absolutely no color shift with the Singh-Ray, but a large one with their competitor. These images were taken about 2-3 minutes apart, using identical camera settings.