One Flash, Multiple Frames

I've dabbled in HDR a few times. One of my first posts on this blog was about HDR using RAW images from my Canon PowerShot point and shoot camera. I knew a lot less back then, but I certainly had the photography bug. The resulting image of that experiment, admittedly, looks like ass, but I took that experience and moved on 'poco a poco'. Now, if you look at my Flickr stream you will see a couple examples of my finer HDR work.

One thing I had yet to try was actually compositing an image out of multiple frames rather than using tone mapping. So, last month when I saw this funky abandoned structure in Tarifa I thought I would give it a go. It turned out to be easier and more fun than I had expected, but I couldn't have done it without one cool little trick. Keep reading to find out what that trick was.

Compositing vs. HDR

Now, some of you might be wondering "What is compositing?" Well, composite literally means to be made up of various elements. So compositing is the process of taking more than one picture and making one image out of the bits you want. But, how does this differ from HDR? Well, HDR uses something called tone mapping which 'maps' one set of colors to another. This allows you to choose between a wider set of color ranges to compensate for too-bright or too-dark regions in your scene. This means you can expose for both your sky and your foreground and get some really amazing colors.

When making an HDR image, you typically have a static scene, or else you get weird ghosting artifacts. When making a composite image it doesn't really matter, because you get to choose which parts of the frame get included. In my original pictures (19 used for this image) the pop of my flash can be seen at least six times, and yours truly appears more than once as well. And although some of the better HDR programs can compensate for this, I wouldn't have had as much control over the finer details without being able to mask areas like I was able to here.

How I Did It

I stumbled upon this scene while scrambling to catch the last of the sunset on our overnight

trip to Tarifa. Tarifa is the southern most tip of Continental Europe and juts right out there into the Atlantic, pointing towards Morocco. It's only 10 miles from the Moroccan coast and about 18 miles from Tangier, as the crow flies. It's also where they hold the kite surfing and wind surfing world championships. To say it's windy is an understatement, but luckily it wasn't windy on this winter day.

As you can see, the weather was hardly conducive to taking sunset pictures, so when we came across this monstrosity I thought "What the hell!" I promptly set up my tripod and

took some shots, exposing to the right while preserving my highlights. Here's an example of what I was getting with that straightforward approach with a before, straight out of the camera (only cropped), and after (processed in Aperture and Viveza).

I admit the sky certainly looked a lot better 5 minutes later when I took my composite images, but other than that I can see that the structure i

s lacking in detail. The diffused light doesn't really give me the detail I'm after. This was when I remembered my strobe. I knew I wasn't packing all that crap around for nothing! As Joe McNally says, your gear doesn't do you any good sitting back in the studio. I promptly pulled out my hot shoe flash, whacked on a radio trigger and called in my support. I had Ellie (my wife) press the shutter while I walked around aiming my strobe at certain areas on the structure. I tried getting some bursts a bit farther back, but I soon reached the distance limit of the Cactus V2s'.

The Trick to Making Great Composites Really Quickly

Here's a screen grab of the 19 images I used to make the composite. I opened all of them as 16 bit TIFFs, then copied each one and pasted them all into one single file one at a time.

As you can see, there's a bit of detail in each image, but none of them make a very good pic on

their own. So this is where one little trick can save you a lot of time. All I needed to do was set the blend layer of every layer (except bottom layer) to Lighter Color. Magically, all the lighter areas of all the layers were exposed. Then I went through each layer, created a mask and eliminated the areas I didn't want to show, such as myself, my flash and the areas where the clouds overlapped. Once I had my composite made I selected all layers and pressed Shift+Alt+Cmd+E (Replace Cmd with Control on Windows) to create one new layer from all the others. After saving I discarded all the previous layers and was left with one nice manageable layer. Also, deleting all the other layers dramatically reduced my file size which saved more than a few RPMs on my scratch disk.

From here I was able to create my typical adjustment layer masks to make local changes to the sky and the structure. A quick trip into Viveza and a final stop at Noise Ninja and I was now ready to save back into Aperture for the final touches.

I really like how this turned out and it almost seems a bit richer in tone than your average HDR. I think that's because I wasn't really messing with compensating for my shadows and highlights, I was just adding in touches of light where I wanted them on my subject.

What Would I Change?

If I were to go out and do something like this again, the first thing I would do is make sure to pop my flash in EVERY possible area within the frame. The bottom left corner in this image could have done with at least a bit of light, but I didn't realize this as I was looking through my pics on the back of the LCD. The other thing I would have done is fired my strobe through an umbrella. I did have the flash set to wide zoom, but I would have liked a lot more falloff at the edges of my beam of light which would have avoided some of the hot spots.

What do you think? Have you ever tried a composite image? Share in the comments, I'd love to see what everyone else is doing.

-CB