Mastering digital long exposure photography
If your new to digital photography or still relying on an exposure app or chart then this post is for you!
So you have mastered your camera and can now shoot 30 second exposures without an issue, but what happens if your shooting at night and it is darker or maybe your using a Big Stopper ND Filter and require longer exposure times? If your answered ‘guess'; then you know how much of a pain this can be when you guess incorrectly and miss your shot with an extremely under or over exposed file.
If you answered ‘I use an App'; then that’s OK, but there is an easier way. A way that doesn’t require anything other than your camera.
For all of my Long Exposures over 30 seconds I use ISO 6400 to carry out my test shots. That way my test shots to get the correct exposure times are only seconds long and not minutes. There is no guessing and I can quickly see the histogram.
So remember this: At a constant Aperture; by using ISO 6400, whatever the exposure time is in seconds will be in minutes when you reduce back down to ISO 100.
Now for long exposures using ND filters the camera metering will be a little out so if you try to correctly expose using your camera meter then your image will be dark and your histogram will be all the way over to the left. So you will need to carry out a few test shots ignoring the camera meter and increase the exposure seconds as you go until the histogram is where you want it. Make sure your view finder is covered to stop light entering the camera too!
e.g If f/14 ISO 6400 6 Secs = a correctly exposed histogram. Then f/14 ISO 100 6 Mins = a correctly exposed histogram.
The below example is a RAW file captured at Merewether Ocean Baths and is my 6 second test exposure at ISO6400. I wanted my histogram to the left because the sunlight was increasing rapidly and knowing it was going to be a 6 minute long exposure I didn’t want the increasing light to blow out the white blocks
The next example image is the RAW file captured after lowering my ISO back down to ISO100 and changing my exposure time to bulb and then shooting a 6 minute exposure. The histogram didn’t move as much as I had anticipated during the 6 minutes (but better to be safe than sorry!)
The last image is my edited version including the histogram. I have brightened the exposure, corrected the white balance and used a number of different techniques to increase colour and saturation.
Now I have used f14 in my example but it doesn’t matter what aperture you use, providing you are consistent and whatever aperture you use for your ISO6400 test shot is the same when you take your ISO100 shot. Hopefully this post helps you with your long exposures! So get out there and have a go and make sure you let me know how you go!Regards, Kiall Frost