Get High on Dynamic Range – HDR

Posted in Photography Tricks on December 26th, 2010 by MadDog
No Gravatar

I’ve purposefully laid low during the Christmas holiday. I believe that this has been good for me. I know that some of my friends are concerned that I’m becoming a hermit, but that is not the case. In the last few months I’ve attempted to socialise normally, sometimes at the expense of my well being. Living in an atmosphere which relentlessly reminds me of my loss has not been easy. Normal social gatherings have been difficult.

Anyone who has suffered a loss of a spouse knows exactly what I’m talking about. Loneliness is intensified by being with loved ones who shared the life experience of knowing the person who once occupied the empty chair. One can feel very much alone even when surrounded by friends. At some point a decision must be made whether to continue to suffer that pain or to retreat for a while to allow strength to recover.

After the holidays I will begin to behave normally again. The time of relative solitude has been good for me. It’s allowed me to gather my wits and gain a fresh perspective. I’ll soon be starting a new year. Life will not be rosy. I don’t expect that. There could still be major setbacks. However, I have accomplished much. I’ve taken control of many aspects of my life with which I was formerly out of touch. I’ve renewed my faith and strengthened it. My plan for 2011 is to recover as much as possible of my life here in Madang and shape it into something which will allow me to be a full person again. There is much which I have left behind and more yet will have to be considered as to its usefulness to me in the future. However, I can see that my future, though seen through a glass darkly, has promise. It is a different promise from any which I formerly imagined. But, it is not dark of necessity. I do  have within my power, trusting in my faith, that I can make it bright if I take the right path.

Through a dear friend I got an offer of a small photographic shoot for Coatwatcher’s Hotel here in Madang. I was happy for the work, though it was not an easy job. As I was working on the images I experienced a sudden geek attack and decided to devote a post to the technique involved. Sudden geek attacks cannot be ignored.

Here in this image you can see the problem. This is a shot of the hotel dining room looking out over Astrolabe Bay:

As you will note, it’s not very exciting or aesthetically appealing. In fact, it’s downright ugly. What’s the problem? Well, the problem is that a lot of light is in the wrong places. This is a typical back-lit image. The camera cannot cope with the huge dynamic range of light levels varying from very bright to very dim. Our eyes adjust constantly to allow us to take in this range of brightness levels. Viewing this scene, you would be perfectly able to see all of the dark areas. As your eyes rise to the bright light outside, your eyes will compensate automatically. No camera can do this.

So, how can a photographer without complex and expensive lighting equipment take a decent photograph of this scene? A fantastic trick became available to photographers with the dawn of the digital age of cameras and powerful computer processors which can do the maths. It’s called High Dynamic Range Photography. In theory, it’s pretty simple. Anybody with a decent camera and a computer can do it. I wrote a post on HDR a couple of years ago.

The first image was what one might call a “normal” photograph. I simply set my Canon G11 on an automatic setting and took the shot. The result is miserable. However, what if we could take several shots, adjusting the camera for each level of brightness, and combine the best exposed portion of each frame into one image? That is exactly what HDR photography is all about.

I first set my camera to get a well correctly exposed image of the outside area including the sky and water of Astrolabe Bay. It’s even worse. The inside is completely black:

Next, I took another exposure with the camera set to capture the dark levels inside the dining room:

That’s just as bad, except that you can now see the areas of the image which were nearly black. However, the outside area is completely washed out. I had my camera mounted on a tripod for these three shots. It’s important that the camera does not change angle or distance to the subject. The software needs details of the images to remain in the same position on the frames so that it can match the images up perfectly before it begins the task of selecting the best exposed areas of each image to combing in the final HDR shot.

Then, using the Merge to HDR image of Photoshop, I combined the three images to produce this one:

This is a perfectly useable image for the calendar which the client wanted to produce. I’ll now collect my pay.

It is a characteristic of HDR photography that most images appear a little strange to our eyes. We are not used to seeing such a compression of dynamic range. It really looks more like a painting than a photograph. However, for the client’s purpose, it was the only way to get the shot.

Just for fun, I set up my tripod in my bedroom and took three shots of my little corner office. This is the underexposed shot:

I won’t bore you with the overexposed shot or the auto setting shot. That would be tedious.

This is the combination of the three images:Certainly, I could have used flash to capture the same image, but that would give the shot that flashy, unreal effect which I don’t like. The colour tones are rather sickly, because of the colour of the cloth on my curtains. I didn’t bother to correct it. I wanted it to look exactly the way my eyes see it. I’m going to change to white curtains!

One does not absolutely have to use a tripod, given reasonably steady hands and firmly planted feet. I took a stroll up at Nob Nob mountain the other day with a friend. I’ll have some nice nature shots from that visit in the next few days. They sky was cloudy and the light was miserable, not what you want for landscape photography. I shot two images. This one is correctly exposed for the dark foreground vegetation:

This one is exposed for the sky:

Even with only two exposures Photoshop did a credible job of producing a useable image:

It’s not going to win any contests, but it’s a nice picture. You might note some funny colour fringes around one of the clouds at the upper right. It’s an artefact of the merging process. I didn’t bother to correct it, because it’s a good example of some of the problems which can crop up out of the blue, so to speak.

If you would like to see more examples of HDR photography, try here and here. Some of these I like and some I very much do not  like. Certainly, HDR has a place as an artistic tool. However, if taken to extreme, it gets tiresome very quickly. So many shots look like cheap posters.

Okay, now I’m going to make some cheesy, cheap poster shots. I can hardly wait.

Tags: , , ,