Learning HDR Photography

I first heard about HDR when I read about an iPhone app that took multiple photos and combined them into one for increased tonal range. When I started looking into HDR I found that there is a LOT more to it, and a lot of ways to do it. Some people have the patience to combine 9 separate exposures in Photoshop and mask each one to get the best exposed areas of each image. I really wanted to try it, but I don’t have that kind of patience.

Then I discovered software programs like Photomatix, which combine the multiple exposures for you. Then you can make adjustments for the look you want. After studying HDR technique and trying a few of these software packages, I settled on NIK HDR efex Pro. I think it is the most flexible and it is very easy to use. It has a nice big preview window so you can easily see the results when you experiment with the sliders and adjustments.

The basic idea behind HDR (High Dynamic Range) is to get a broader range of tones into your picture than would be possible with a single exposure. Digital camera sensors are more like slide film than negative film, in that they are more contrasty and less forgiving of exposure variances. Digital sensors have a limited dynamic range, from dark to light. At some point the shadows and highlights lose their detail. So the trick is to take multiple photos of the same scene, underexposing some, overexposing others, and then combine them in software to get the detail in shadows and highlights back.

Here is what a typical HDR photo looks like. The Washington State Capitol is not far from my house and I took this the other night.

WA State Capitol HDR

WA State Capitol HDR

I don’t particularly care for this look, but I’ve seen a lot of HDR images that have this highly stylized appearance. I prefer my photos to look more like what I saw when I was there – more realistic. But I value HDR for being able to keep the light parts of the image from blowing out and the shadows from blocking up. So this is my version of the same photo.

EOS 7D - 2.5, 8, & 25 seconds @ f/8.0

EOS 7D – 2.5, 8, & 25 seconds @ f/8.0

I used the EF 17-40mm f/4.0L lens at 17mm and set the ISO to 100. Because of the extreme wide angle, there is some distortion, like the flag poles curving inward. But I like this smoother and more natural look. I prefer shadows to be darker but still have detail.

Just for comparison, here is the n0n-compensated, non-HDR, single exposure.

Non-HDR, 8 secs

Non-HDR, 8 secs

This single exposure (a RAW file adjusted in Apple Aperture) is also a good picture.  In fact, I’d say that it’s highly subjective at this point. Do you like the smoother, more neutral non-HDR, or the more saturated and coarsely detailed HDR?  The color saturation could be adjusted after creating the HDR from the three exposures, but I like it the way it is.

If you look at the darker parts, like the lawn and fence on the right, you can see the HDR has detail that the single exposure does not. Those came from the over-exposed shot.

Here is another HDR shot of the lake down the hill from the Capitol. The longest exposure was a full 30 seconds.

Capitol Lake HDR

Capitol Lake HDR

I’ve read that combining more exposures with less variation between can give better results. I’ll have to try that and report in a future post. Because I have a Canon instead of a Nikon, my auto-bracketing is limited to 3 exposures at a time. So I could do (-2, -1, 0) and then shift to (0, +1, +2) and delete the extra “0” exposure to get 5 shots.

Off topic, but I have to say, compared to my old EOS 10D, the 7D is MUCH better with noise reduction on long exposures at night like this. And it has three times as many pixels on the same sized sensor, which means they must be around 1/3 the size of those on the older camera. It has an APS-C sized sensor, after all, not a full-frame sensor like the 5D or the new 6D.  A larger sensor with similar resolution means that the individual “photo sites” on the sensor can be bigger and better at gathering light, but as you can see, the smaller APS-C sensor still does a great job.

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