Just like many other aspects of photography, the answer to the question above is largely situational, and sometimes not adding light is the answer. I’ve already talked about how using off camera flash for astrophotography can improve your images, but what if you don’t have a flash or simply prefer to use an LED instead? Below I’m going to argue that you should use both for different situations, and it won’t cost you an arm and a leg to get the gear you need.
Let’s recap on why adding light to your Milky Way images can be a good thing. In short, when you add light to an otherwise dark scene, your camera captures more information at a higher quality than can be achieved without adding light - in most situations. Our goal when capturing images should include technical soundness, in addition to the other elements. We want our images to look good in a final, large format print.
If you’re in a dark sky area, with little to no light pollution, your shadowed areas of the image can end up noisy or grainy in the final edit. This is mostly due to the high ISO settings used to help capture these nighttime scenes. When trying to manipulate this high ISO image in post production, it can result in some unwanted shadow noise or grain. At lower ISO settings, your camera can typically produce a higher quality image after bumping the shadows in post production for daylight scenes. However, we need the high ISO to capture the details of the Milky Way and using lower ISO in a dark scene will simply not capture enough light information to make a useable image. Adding light to the foreground is the best compromise to this obstacle that can result in a well-exposed final image.
I typically use a flash when my subject is static and can easily be lit from the side, and at the angle I desire. Using a flash to light your scene will freeze moving subjects, like this wave crashing in the photo. This can be useful for seascapes if you wish to capture moving water and simulate a fast shutter speed. It will create a high speed effect, freezing the water. If you have a moving human subject, the flash will burn the exposure of the subject into the frame. If they are standing in front of a light background of sky, the flash exposure will make the subject appear ghost-like. Using a flash offers very repeatable results and takes the guesswork out of the added light exposure.
The best part is that you don't need any fancy flash accessories or equipment. Any old flash will do the trick, as long as it has a "test" button. Simply position your flash as desired and press the test button during your long exposure to add light. Adjust your flash power and angle to taste.
When photographing a shallow cave, it can be difficult to get an even exposure of the cave mouth using a flash. This is when sweeping an LED over the foreground can be the answer. A deeper cave would allow you to move back farther and fire the flash evenly on the rim of the cave. Keep the light source moving to avoid over-exposing an area, to help soften shadows, and to keep the lighting more even.
Using an LED to light a seascape will give you a soft, almost ethereal feel to the scene compared to the harsh freeze-frame effect of the flash. I prefer to use the LED at high power and only light the water for a few seconds as a wave is splashing over rocks in my foreground.
Deciding how you want the light source to interact with your scene will determine your choice of LED or flash use.
If your subject is static and you have ample room to position your light source, either LED or flash can get the job done. As soon as you have a moving subject in your foreground you should stop and think about which light source will yield the desired result; flash to freeze your subject or LED to show the movement.
•Use a warming gel with any light source to better match the white balance of your scene and the night sky. Set your white balance manually to approximately 3800K and use an orange/warming gel on your flash or light source. Some LED panels come with an orange filter. Adjust your white balance to taste.
•Positioning of your light source can have a huge impact on the mood of your scene. When the ground has interesting texture, hold the light source down low to accentuate sand dunes, grass, or rock formations. Holding the light directly above your camera gives a flatly lit effect like a mugshot. Consider holding the light at about chest level and off to the side of your scene can produce nice, practical lighting over your foreground.
•If your light is too concentrated to one side of your image, causing a bright spot, you may need to back away from the foreground with your light. The further away your light source is from your subject, the more evenly lit it will be. However, when you scoot back your light will appear more dim. After scooting back, turn up your flash power to compensate.
•If your camera has a highlight alert feature, switch this on to determine if your are over-exposing your scene with your light source.
•Check your shot for unwanted shadows cast by your light source onto the scene. You might catch your tripod in the shot!
•Experiment with timing your flash burst during the exposure. When you "pop" the flash will determine the look of the image. Time it with the crashing wave or other movement.
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