When to Bump Up Your ISO

Okay, so we know we’re going to be at around 15 seconds for our shutter speed, and generally when we’re on a tripod, we try to keep our ISO at its lowest number (usually 100), but this is one of those cases where, to bring out the dimension and detail of the Milky Way and stars, you’re going to need to crank the ISO. Start at 1600 ISO and see if the Milky Way and stars look bright enough to you. You might need to crank it up to 3200, which I know sounds high, but luckily, most of your sky will be very dark, so the small amount of noise that does appear will be just that—a small amount of noise. Take a test shot at 15 seconds shutter speed, ISO 1600, and see what you think. You can always raise (double) it and see how that looks for you. A 6400 ISO is as high as most folks will want to go, unless your camera is notoriously clean at high ISOs like this. Also, remember, we’ll be doing some serious post-processing later on in Photoshop or Lightroom, so if your sky image just looks a little dark overall, don’t sweat it—we can brighten things quite a bit in post while limiting the amount of noise.