Long Exposure Photography Lesson 3 (Of 4)
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© Beth Ruggiero-York Long Exposure Photography Lesson 3 (of 4) 1) Night landscape photography a) Stars as points b) Star trails 2) Assignment Night Landscape Photography All night landscape photography is long exposure photography because it is dark. For this reason, no filters are needed or should be used. The dark is acting as your filter. I have divided this category into two types – stars as points and star trails. Both are long exposures, but star trails are longer exposures of a similar scene. Star tails, also known as star streaks, are the result of a long exposure that includes a starry sky. So why do the stars trail? Since the earth is moving to the east, the stars appear to move to the west. It’s not the stars that are moving; it’s us here on earth. “Stars as points,” on the other hand is a bit of a misnomer. Because the earth never stops moving, the stars will always show apparent movement in a photograph. The key is to use an exposure time that is short enough that the star movement or ‘trailing’ cannot be detected by the human eye in the resulting image. The keys to shooting these special types of long exposures are discussed in detail in this lesson. © Beth Ruggiero-York • Night landscapes with stars as points in the sky When photographing night landscapes when your goal is to have the stars appear static, or as points, there is an easy rule that will help you find a starting point for the exposure time that will keep them as close as possible to points (rather than trails). It is called the 500 Rule: Divide 500 by your effective focal length* to get the approximate maximum number of seconds you can expose before the stars begin to trail * Effective focal length takes into account whether you are shooting with a full-frame camera or crop-sensor camera. If using a full-frame camera, then the effective focal length is the nominal focal length of your lens (e.g., 25 mm = 25 mm). However, if you are using a crop-sensor camera, then you need to calculate the effective focal length by multiplying the nominal focal length (e.g., 25 mm) by the crop factor for your camera. For Canon, the crop factor is 1.6; for Nikon, 1.5; Sony, 1.6; Olympus, 2.0, Pentax 1.5, etc. So, for a Nikon crop-sensor camera, for example, the effective focal length for a 25 mm lens would be 25 x 1.5 = 37.5 mm. As indicated, this is only a starting point, and often you will need to decrease the exposure time to keep the stars from trailing unacceptably. The point at which the trailing is no longer acceptable when you zoom in on the image on the LCD monitor is very subjective. There is no right or wrong exposure time; however, you will need to consider how large you may want to print an image when making the decision. If you hope to print a very large image, then you may want to reduce the 500 Rule to the 400 Rule or even the 300 Rule so that the trails are less apparent. Remember that by doing that, you reduce your exposure time to the point that you may have to increase the ISO to get the light needed onto your sensor for a correct exposure. This is a trade-off and one that must be considered. © Beth Ruggiero-York The 500 Rule EFFECTIVE FOCAL APPROXIMATE MAX LENGTH EXPOSURE TIME 14 mm 36 seconds 20 mm 25 seconds 24 mm 21 seconds 35 mm 14 seconds 50 mm 10 seconds 100 mm 5 seconds 200 mm 2.5 seconds 300 mm 1.67 seconds 500 mm 1 second It is important to take into consideration the direction that the camera is pointed. If pointed north or south toward the poles, the stars will appear to move more slowly, giving you a little more wiggle room with the 500 Rule. If you are pointed east or west, however, the stars will appear to move more quickly, and you will have to be more conservative than the 500 Rule allows. 25 sec, f/2.8, ISO 4000 No filter Nikon Df, Zeiss 25 mm f/2 lens © Beth Ruggiero-York • Star trails It follows the explanation of stars as points that the longer you open your shutter, the more the stars will trail. The trailing is not random; rather, it is in rotation around the poles. So if you point your camera to the north in the Northern Hemisphere or the south if you are in the Southern Hemisphere, the resulting long exposure will show circular star trails around the pole. 2601 sec, f/4, ISO 200, 21 mm Nikon D7100, Nikkor 14–24 mm f/2.8 lens @ 21mm effective focal length Taken in Rhyolite, a ghost town in Nevada, this is a single long exposure lasting approximately 43 minutes facing just east of north. Polaris is the star that © Beth Ruggiero-York appears almost at the center of the star trail circles, indicating the northerly direction. In the Northern Hemisphere, we have the advantage of a star very close to the actual pole called Polaris (aka, North Star) to help us locate the North Pole. By locating Polaris, you can plan your night landscape composition to include circular star trails in the background sky. The apparent movement of the stars as the earth rotates is about 15 degrees per hour horizontally; they do not move vertically. To locate Polaris, you must first find the Big Dipper in the night sky. Follow the two stars at the end of its ladle upward to the last star on the handle of the Little Dipper – this is Polaris. Follow the two stars at the short end of the ladle of the Big Dipper upward to the first star on the handle of the Small Dipper. That first star is Polaris. Another helpful fact for finding Polaris is that its altitude is at the same number of degrees as your current latitude in the Northern Hemisphere. For example, at approximately 33° north in Phoenix, if you look up 33° in a northerly direction on a clear night, you will find the approximate position of Polaris. To shoot long exposures of star trails with any type of foreground requires some preparation, which was discussed in Lesson 1 under the “Technical Stuff” section. Be sure to have the needed camera gear and review the focusing © Beth Ruggiero-York techniques. Just as important is to scout out your shooting location while it is still light. Night photography has its challenges to begin with, but setting up and composing in the dark just compounds the challenges. Find your desired location ahead of time in daylight, walk the site and determine possible compositions. Look for hazards in the terrain. Below is a detailed description of what items you need when photographing after dark and how they will serve you. Night Photography Equipment One of the most common initial questions students ask when taking their first steps into the field of night photography is “What equipment do I need?” The answer is that, while greater capability and flexibility come with more advanced camera bodies and lenses, you can create excellent images with entry and midlevel DSLRs with moderately priced lenses. For the type of night photography being addressed in this book, however, I would not recommend a point-and-shoot camera. Here is a list of equipment I recommend. Required items are marked with an asterisk: 1. *DSLR with Bulb Mode capability (ability to expose for over thirty seconds with the use of a remote release) One of the advantages you gain with the newer, higher-end DSLRs is better high-ISO capability. With the longer exposures required for most night photography, your camera’s ability to handle high ISOs cannot be ignored. Additionally, it is generally recognized that a full-frame DSLR is the best choice for night photography due to better high-ISO handling, rather than a crop-sensor (APS-C) DSLR. As I indicated above, though, this absolutely does not mean that your crop-sensor camera can’t be used for successful night images; I am simply pointing out the preferred tools. 2. *Sturdy tripod This is just as important as the DSLR. I have seen way too many students struggling to set up their cameras on flimsy tripods with extended center posts. There are good-quality, stable tripods available for a reasonable price (e.g., Induro, Vanguard, etc.). Of course, if your budget allows, Gitzo and Really Right Stuff are the highest quality. Ideally, your tripod will be tall enough when fully extended for you to stand © Beth Ruggiero-York behind it at eye level without having to bend down to look through the viewfinder. Many smaller and less expensive tripods have a center post, a column that extends upward to increase the height of the tripod. If your tripod does have a center post, using it should be avoided because it creates a less stable platform for the camera. If you have no choice but to use it, there are ways to stabilize any tripod that are worth considering. One is to hang your camera bag from the hook that is attached to the bottom of the center post or, if your tripod does not have a center post, the hook is where the tripod legs meet at the top. Not all tripods without center posts, however, have a hook, but you can add an after-market hook.