Monday, August 16, 2010

I Love Thunderstorms!

I said that before. About a month ago. At the time I said I remembered having a multiple-lightning-hit phot from years ago and that I'd post it here when I find it. I will: I just haven't found it yet.

But last night, there was a thunderstorm. There was a lot of lightning going on, but not right overhead. It was a really active storm, but the lightning was cloud-to-cloud, not cloud-to-ground. The storm centre had passed and it wasn't raining that hard. OK, I grabbed the camera, the tripod, an umbrella and headed out into the back yard.

Without further ado, here's what I got:

This is a 5-shot multiple exposure taken over the course of about 5 minutes. Any time the shutter was open for more than 15 seconds, I had to wait the same length of time for the noise-reduction process to complete. Frustrating, because I wanted to press the button again!

If you want to try this at home, here's what to do. This is for a nighttime shoot: all the numbers go out the window if you're shooting during the day. I think it's do-able, but you'll have to experiment to avoid light polluting your images.

The setup
  • You need a tripod. Ideally you should also have a shutter release cable (mine was in the house, but I wasn't going to leave the camera out in the rain without an umbrella to go get it!).
  • Find a spot where your camera isn't going to get rained on or take a chance and use an umbrella.
  • Use a relatively wide angle lens. You don't know where the lightning is going to be and it's good to include something other than sky in the shot. Find a way to focus on infinity then switch to manual focus. Don't forget to turn off the VR if you have it, when you're on a tripod. I forgot.
  • Set the ISO relatively low. I happened to use the minimum (ISO = 100) but that's not necessary. I also opened the lens all the way (f/3.5 in this case) but if I were doing it again, I'd use f/8 and an ISO around 250.
  • Set the shutter to "M" and use the 'bulb' setting so it stays open as long as you hold down the shutter.
Shooting the pictures

OK. What we're shooting for (pardon the pun) is a single frame with a bunch of lightning bolts in it, or at least one spectacular one. Since my session was a passing storm and there were no really good cloud-to-ground bursts, what I was planning to do was to shoot several frames and then sandwich them together. That only works if you take care not to move the camera between shots.

My typical exposure time was in the 15-30 second range. I was trying to stay under 15 seconds as I mentioned above, but generally that didn't work. Since there was about 5 seconds between lightning events, I waited for one, then pressed the shutter release a few seconds later and held it down until there was some activity. Not just one hit, several, if I could get them. I seldom actually saw the lightning bolt itself, just the flash in the sky, but the sensor picked it up!

Shoot, hold for some events, release, wait for the NR process (this may be a Nikon thing. I don't know about other brands). If I didn't think there was anything going on, i tried to beat the 15 seconds or I switched the camera off and back on again to defeat the NR delay and take another shot.

I was out for about 15 or 20 minutes, until the storm had moved off to the east, out of sight. Inside, upload the images to the computer, check them out and select good frames in Lightroom.

Sidebar: since there's a thunderstorm going on, you did shut down your computers, didn't you? I actually didn't, but mine are plugged into a UPS (uninterruptible power supply) with superb surge protection. Won't help if you get a direct lightning hit, but it's pretty good otherwise. Get one. They're inexpensive. They're heavy, though — all battery — so get one at the local computer store instead of trying to ship it from somewhere else.
Post Processing

If you're using Lightroom, you can select the images of interest, right-click, choose "Edit in Photoshop" and select "open as layers". Or you can do it manually, your choice. Now unless you do something, the only layer that will be visible will be the top one, but it's a simple task to select a blending mode that works. For me, that was "Lighten". I went through all the layers and set them to this mode which made all the lightning bolts visible!

Occasionally that didn't work, so I turned off a couple of layers, or played with them by adding a layer mask and painting on it. My main concern was that the clouds had moved between shots and I wanted to see the better formations. This took a bunch of fiddling. I discovered that using a soft brush with low opacity made things blend better.

Night shots are blue. Not that there's anything wrong with that, but I didn't think it conveyed the "heat" of a thunderstorm. After saving the image as a multi-layer .psd file, I flattened it, then converted it to greyscale (black and white). Just for fun, I ticked off the "tint" box and lo and behold, up came this rich golden orange colour. Save it, back to Lightroom to crop and tweak some exposure values, and we're done.

If most of what I just wrote is Greek to you, then you should join NAPP and learn a bit of Photoshop. Most of what I did would be considered "basic". If you have a good lightning bolt shot in your own portfolio, I'd love to see it, because
I Love Thunderstorms!

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