Since releasing this image to the public I have had countless emails in regards to how I created this photograph. Obviously I needed a long exposure in order to capture the stars, color, and detail in in the lighthouse. Too long of an exposure and the stars begin to trail. Too short of an exposure and the image becomes various degrees of featureless black.
Maybe the best way start is to list off my camera settings here. Due to the low light in the scene and lack of contrast, there really is nothing for the autofocus of a camera to latch on here. So to begin with, I switched over to manual and set my focus by headlamp to just under infinity. Why just under? Well that’s one of those unique characteristics that only time spent learning your lens can tell you. I was shooting with a Nikon 12-24mm lens and I have found that I produce sharper results in situations like this when just slightly backed off from infinity.
Next, I needed the absolute most light that I could possibly get out of this scene. So, I did two things. I set my aperture to f/4 and my ISO to 2500. I could have gone higher with the ISO but I made this image with a Nikon D300 which in my opinion gets really funky at anything higher than 2500.
Now I shoot everything in RAW, as you should as well. With the D300 there is the option to shoot in 12 or 14 bit NEF files (which is Nikon’s version of a Raw file). There has been a lot of debate and testing done over 12 bit vs 14 bit since Nikon started offering this option. Some may argue with me on this, but I like to make things simple on myself. For me, 12 bit is for shooting wildlife, 14 bit for landscapes. At 12 bit on the D300 I can shoot at 6-7 frames per second. At 14 bit this drops down to 2.5 frames per second. So just looking at the fps of the camera, it’s a no brainer as to why I use 12 bit for action. The 14 bit on the other hand has been argued to produce almost imperceptible differences in quality than the 12. This is 100% true with a well-lit and properly exposed image. Once you begin to push the limits of your technology and shoot in low light situations, this is where the 14 bit NEF file really begins to stand out – especially when shot at high ISO settings like 2500. I actually have this option set in my custom menu to make it easier to get to on the fly. There are so many options in cameras now a days that I don’t have time to sit and memorize where everything is buried in the menu options. So, I just set the ones that I use a lot to a custom menu in order to pull up quickly.
As for my shutter speed I photographed this a 30 seconds. This is as long of an exposure than you can do before going to BULB and needing shutter release cable and timing the exposure yourself. This however, is not why I stopped at 30 seconds. I knew that first and foremost, I wanted to capture the stars as tiny little pin pricks of light in the sky – not star trails streaking through the night. Well there is actually a formula you can use very quickly to determine what the longest possible exposure you can use before you begin to get star trails. Some like to call this the 600 rule. Basically all you do is take 600 and divide it by the mm of your lens setting that you will be photographing at. This will give you your maximum exposure time.
As I mentioned above, I was photographing with a Nikon 12-24mm lens. I had my lens set to 14mm which with the digital cropping factor of the camera I was using would have the equivalent of 21mm on a full frame camera. How do know this? Well, I know my sensor has a 1.5 crop factor so I multiply 14 by 1.5 to get 21. ANYWAYS . . . I then take this 21mm and divide it into 600. The rounded results are 29. So, I know that beyond 29 seconds, star trails will begin to show up. A 30 second exposure then, will do just fine as a 1 second variation from this will matter little. If on the other hand I had stopped down 1 full second than obvious trails would have been created.
Now, there is absolutely no reason in the world for you to have to do this every time your out shooting. Most likely you have only small selection of lenses you will probably ever be shooting night scenes with to begin with and so all you really need is a rough idea for each one of those lenses. With my 12-24, I know that I have 30 seconds on the wide side and 15 seconds on the narrow side of my focal range. Keep it within that range and you are golden!