Realistic HDR photography

Limited dynamic range is something that plagues many photographers who have gone digital. Or rather, the range itself isn't a problem per se; the problem is with how the two different media perform at the limits of their range.

I don't know the mechanics behind dynamic range, but that doesn't matter here. What matters more to me as a photographer is how they look.

Digital systems tend to clip highlights in a very abrupt manner. Film tends to handle the highlights in a more gradual, elegant manner.

But frankly, in today's day and age, most of us wouldn't want to commit the time to shoot in film. Digital systems simply provide too many conveniences. Solution? High dynamic range (HDR) photography.

First, a note on HDR photography in competitions. HDR photography can either be a multiple exposure technique, or a single exposure technique. The multiple exposure technique involves taking a series of images of the exact same scene with different exposures (such as EV-2, EV0, EV+2), or taking a single RAW image and then manipulating it to make three images of "different exposures". In other words, the first technique would, strictly speaking, be disallowed for competitions requiring entries to be made from a single exposure. The second technique may yield less desirable images, and will most probably present a grey area in such competitions.

We've most probably seen some stunning examples of surreal-looking HDR photography. These are most probably the result of tone mapping by plugin (for Photoshop, Lightroom, Aperture etc) called Photomatix Pro.

By hto2008 on Flickr

Results from Photomatix Pro are easily identifiable - incredible detail in the entire range of the image, and often saturated colours. Aesthetically, this may or may not be desirable depending on what you wish to achieve. Clearly, however, Photomatix Pro isn't an option if more toned down or realistic HDR images are required.

Thankfully, Photoshop has its own HDR funtions that do a pretty good job.

I'm working with Photoshop CS4, but most recent versions should be similar. My tutorial will be based on three separate JPEGs taken handhleld at EV-2, EV0 and EV2 using the bracketing function on my D5000. When the shutter release is held down, what the exposure bracketing function does is to take quick successive exposures in the pre-defined increments (2 stops in my case). White balance exposure is also available on my camera, but I haven't really found a use for it since the Auto WB does a good enough job for me most of the time.

If you require more detail in the final image, some cameras may have a bracketing function for up to 5 images, or you're really going all out and require even more, or if your camera doesn't have a bracketing function, you'll need a steady tripod and a static subject so that you can set the exposures manually.

Go to File>Automate>Merge to HDR. This brings up the following dialogue box.

Browse for the desired images, and if you've taken your shots handheld, check the "Attempt to Automatically Align Source Images" box for Photoshop to line up your images (since they composition wouldn't have been identical due to shake). This works very well for most of the time, but when it does occasionally fail, you'll have to align and crop your images manually by overlaying them on each other.

When you click "OK" after you're done, this appears:

First thing you'll have to to do here is to ensure that the Bit Depth is set to 32 bits/channel. Even though our computer displays wouldn't be able to display this much bit depth, it helps for conversion to an 8-bit image later. Next adjust the slider such that as much detail as possible is visible in your merged result. Remember, the image doesn't have to look good yet, just as detailed as possible. If your merged result just doesn't cut it no matter how you adjust the slider, you may then choose to exclude certain exposures by unchecking the appropriate checkboxes on the left. When you're done, hit "OK".

Now you should be left with a rather unimpressive-looking image. Don't worry, the HDR is there, just that our woeful displays aren't quite capable of displaying 32 bits/channel yet. The next step, which involves the conversion to an 8-bit or a 16-bit image that is capable on our displays, is absolutely crucial.

Go to Image>Mode>8 Bit/Channel (or 16 Bit/Channel if you prefer, but that means some filters for further processing won't be available).

You'll get a dialogue box that gives you four methods of converting the bit depth of the image. Only two of them have settings that can adjusted by you. (Guess what, they're my favourite methods!) As usual, I'm not too sure what the sliders do, but what's more important is that the image looks the way you want it to. So play around with the sliders until you get the effect you want.

In particular, Local Adaptation allows you to adjust the Toning Curve of the image. Play with it like you'd play with a normal curve, except you can be a lot more liberal with clipping the highlights and shadows if necessary since your HDR image has a much larger range than a normal image anyway.

After more processing, this is what I got.

Hope this tutorial has been helpful. As always, constructive questions and comments are warmly welcomed!

EDIT:
I just put my paws on a copy of Photomatix Pro. It can produce realistic HDR images, but the purpose of this tutorial remains. Firstly, it's more convenient to do everything (HDR image generation and processing) in Photoshop. Secondly, local adaptation curves are likely to be more familiar to Photoshop users than the sliders in Photomatix. Thirdly, of course, sometimes you just may not have access to Photomatix Pro.