HDR Tutorial: What is HDR?

Keurbosfontein Window, Cederberg

 

Today I am kicking off the first of a series on tutorials on how I do HDR photography, in the hopes that I might inspire you to do the same. Earlier this year I saw an image which made me go ‘wow’ many, many times, and it turned out that it was made using the HDR photographic technique. I immediately downloaded some demo Photomatix software and started experimenting. I eventually spent a large part of this year learning about the technique and trying to read and practice as much as possible, and now it’s time for me to pass on that knowledge. It’s also just in time for a new year, and maybe for your new year’s resolution to teach yourself a new aspect of photography? It’s not hard, but it does need quite a bit of patience. Let’s get to it!

This first tutorial is an intro to look at just what is HDR or High Dynamic Range photography? Don’t worry about the acronym or the confusing sounding name. Very simply, it’s a technique that allows you to photograph a scene that has complicated lighting. Where there are extremes of lighting in a scene, a camera, whether film or digital, is not able to cope with the lighting range successfully. Photography is all about capturing the light, and that light is often complicated because that’s the kind that impresses us the most.

A very typical example, which is the subject of this post, is shooting an interior scene with a window onto an exterior view. It’s dark inside and bright outside, and your poor camera does not have a clue how to expose this, which makes it quite sad. You can expose for the scene outside the window, but the interior will be as black as the toast I forgot in the toaster this morning. Or you can expose for the interior, but the outside will be bleached out white like you’ve been staring at the sun too long (instead of watching the toast).

Have a look at the before and after slider below to get an idea of the range of lighting in this scene. The darker image is shot at an exposure compensation of -3 and the lighter one is shot at +3. For those that are new to exposure compensation, 0 represents the setting where the camera thinks the scene is correctly exposed, and any + or – setting allows more or less light into the camera than the ‘correct’ setting.

Keurbosfontein Window, Cederberg (underexposed)Keurbosfontein Window, Cederberg (overexposed)

 

Neither of these images works, but there are a couple of ways you could try and tackle this scene. You could maybe turn on the lights inside the house to illuminate the wall if they were bright enough, but this was cottage in the country with no electricity and candles were not going to cut it. You could illuminate the inside wall with a very big flash or studio lighting, but I don’t own either of those, or have much of a clue how to use them. You could take two exposures, one correct for inside, and one correct for outside, and then combine then manually later in Photoshop, which would probably work quite well. But the most fun way to do it is to take a much larger range of photos to ensure that you have the correct exposure for every part of the scene, and then process them all using specialized HDR software. The software combines the images into one composite image that reflects the correct exposure for each portion of the scene. That’s mostly correct, but also a little bit of a lie, because you can also have a lot of fun with the software and create the composite in a number of ways, from fairly realistic to completely lurid and over the top.

Here is the range of images I took for this scene. Using a tripod to ensure all the images lined up perfectly, I shot an 11 exposure bracket set from -5 all the way through to +5, using 1 f-stop increments. That’s probably overkill, and I would usually have shot a 5 exposure set at -4, -2, 0, +2 and +4 for an interior scene like this, but I felt like going a bit overboard on this one. No real reason. I usually shoot with 2 f-stop increments, and for most images with less extreme lighting I shoot a 3 exposure set at -2, 0 and +2. Shooting a bigger set than you need isn’t much of a problem other than taking more time to shoot and more space on your hard drive afterwards.

Keurbosfontein Window, Cederberg (11 exposure set)

 

These images then all get loaded into your HDR software, you get to tweak a number of sliders and settings, and out pops an HDR image. They usually look a little fuzzy and vaseline-smeared when they are freshly made, and need to be cleaned up quite a bit with post-processing in Photoshop before they are ready to show your friends.

Here’s a comparison using the before and after slider of a fresh Photomatix HDR next to the fully cleaned up and post-processed HDR version of the scene. Over the next several weeks, I’ll be adding several tutorials to go step by step through the whole process, from using a tripod through to Photoshop post-processing.

Keurbosfontein Window, Cederberg (photomatix)Keurbosfontein Window, Cederberg

 

By the way, this picture was taken inside the cottage on the charming homestead of Keurbosfontein, close to where I photographed my previous blog image from. There was no electricity here, no cellphone reception, no people, and it was just terribly relaxing! There were beautiful gardens all around the cottage, even though we were in a very harsh and dry climatic area, and it felt like a little oasis.

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