Night Moves – Correct Exposure for Night Photography
“Workin’ on mysteries without any clues, Workin’ on our night moves” -Bob Seger, Night Moves
Last Tuesday, I spent a few hours working on some night photography down on the Ruston Way waterfront with a small group from the Mountaineers. We got quite a few questions about what we were doing down there with cameras and tripods at night. I guess we should have told them we were working on our night moves. But unlike the Bob Seger song, we were working in winter instead of summer. Winter is a great time for night photography because the night comes early, and you can still get home at a decent hour. Of course, it has disadvantages too, like the weather. Though not extremely cold, only about 40° F (about 4° C), it does get chilly standing around waiting on those long exposures.
I’m really starting to enjoy doing night photography. The camera picks up lots of color and detail that the eye cannot see. I recently read Night Photography, Finding Your Way in the Dark by Lance Keimig, and I have a long way to go before ever approaching his abilities. But I have fun. I highly recommend Keimig’s book to anyone wanting to learn more about night photography, it has lots of good information.
One of the great mysteries of night photography is getting the correct exposure without excessive noise. Digital noise is the bane of many a night photographer. Noise increases with long exposures, high ISOs, and underexposed shots. That’s why, with night photography, you should still use low ISOs and exposure for the right side of the histogram (while not allowing any important highlight to be blown out). Shooting this way, will help minimize noise, but will lead to long (or very long) exposure times, very often over 30 seconds (the longest programmed shutter speed on most cameras). Therefore, to get the correct exposure, you will often be shooting in manual mode with the shutter speed set to bulb. Knowing how long to leave the shutter open is a difficult question. It’s a real pain to wait through a 2-minute exposure only to discover when looking at the results that it should have been a 4- or 8-minute exposure.
Here’s one tip I found very useful from Keimig’s book. Set the camera to a very high ISO and take a test shot first. This can be used to check both composition (it’s sometimes hard to compose through the viewfinder in the dark) and exposure. To make the exposure math easy, Keimig presents a chart in his book and on his Nightskye website. Basically, for cameras with a native ISO of 100 (Canon cameras for example), set the ISO to 6,400 and take one or more test shots to find the correct exposure. The number of seconds in the correct exposure at ISO 6,400, is the number of minutes for the correct exposure at ISO 100. For cameras with a native ISO of 200 (like most Nikons), the test shot ISO should be set to 12,800 and the normal shot ISO at 200. (If your camera doesn’t have such high settings, his chart shows how to compensate). For example, I use a Canon camera. So for the featured photo above, I took a test shot at ISO 6,400 and found the correct exposure was 4 seconds. I switched the camera to ISO 100 and re-shot with an exposure of 4 minutes (in both cases, of course, using the same aperture, f/8 in this case). Much easier than guessing on the correct exposure.
Thanks to Lance Keimig, I’ve solved one the mysteries of my night moves!