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ADOBE PHOTOSHOP Lightroom Magazine › ›<br />
One general guideline to avoid star blur is known as “the<br />
500 rule.” Simply divide 500 by the focal length of your lens,<br />
and that equals the longest exposure, in seconds, you can use<br />
before the stars start to trail in your shot. For example, using<br />
a 20mm lens on a full-frame camera, divide 500 by 20, giving<br />
you 25 seconds, the longest time you can expose before the<br />
stars appear to move.<br />
If you plan to capture star trails through a long exposure,<br />
a lower ISO gives you much less noise, and the light absorbed<br />
by the lengthy time exposure can capture the detail needed.<br />
Wide-angle lenses work best to cover larger portions of the<br />
sky, but any lens can be used; just recognize that the longer<br />
the lens, the more opportunity for camera shake, as well as<br />
a smaller aperture that’s tougher to see through, requiring<br />
careful focus and a higher ISO setting. Faster lenses, ones<br />
with larger maximum apertures, are also a benefit since the<br />
wider openings make it easier to see through the viewfinder,<br />
allow more light to hit your sensor, and give you the option<br />
to use lower ISOs for less noise.<br />
To balance artificial light with ambient starlight, the artificial<br />
light you provide, or that’s provided through another<br />
source, must match closely to the extremely dim ambient<br />
light level of the stars. Go outside that limited range and your<br />
exposure is lost due to the difference between an extremely<br />
bright artificial light and low-level starlight combined, hence<br />
an unrealistic final scene or a ton of post work to recover<br />
the image. Waiting for the campfire to lower to a flicker was<br />
the key to this image, while artificial light from a headlamp<br />
was used to add a touch of detail to the glacial erratic sitting<br />
below a star-filled sky. The RAW file was exposed at f/4 for<br />
15 seconds using ISO 1600 with an 18mm lens.<br />
Step Three<br />
› › photoshop user › february <strong>2016</strong><br />
Step Four: Once you have a solid RAW<br />
file to work with, various postprocessing<br />
techniques in Lightroom CC can<br />
help you stretch the capabilities of<br />
your image sensor, pulling out extra<br />
detail while correcting other imperfections.<br />
Using presets to fix night scenes<br />
may not be the best option, as every<br />
situation and exposure requires specific<br />
recovery and adjustments. Take<br />
this Yosemite image of a tent below<br />
the Milky Way. The balance of the tent<br />
glow and the nighttime sky are a bit<br />
high in contrast, but not enough to<br />
lose detail in either area. Initial adjustments<br />
are done in the Lens Correc-<br />
Step Four<br />
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