High Dynamic Range Imaging, or HDRI/HDR photographs for short, are all the rage nowadays — appearing in compact cameras and even on the iPhone 4. But what exactly are they?
When you look somewhere with different levels of brightness, like out through a sunny window while standing in a dark room, your eyes can adjust to what’s both inside and outside. But cameras can’t do that, set the exposure for the outside and everything inside is too dark, set the exposure for the inside and everything outside is washed out.
That’s where HDRI comes in. HDR photography starts with multiple shots of the same scene, exposing for both the dark and light areas. These shots or brackets are then combined in software to create a composite image with both the light and dark areas of the image intact – so you can see more detail than usual in a single shot.
How To Shoot HDR Photos
There are three parts to creating a HDR photo; selection, shooting and post-processing.
Selecting Your Scene
Not everything works with HDRI. Scenes with very little contrast between light and dark areas don’t vary when post-processed. HDRI also doesn’t work very well with lots of moving subjects, as you’ll see strange ghosting effects when combining multiple exposures. So try to shoot mostly static scenes with varying levels of brightness to get a great HDR image.
Shooting Your Scene
Because you’ll need to take multiple exposures of the same scene, you’ll need to shoot with a tripod to make sure the camera doesn’t move in-between shots. If the camera shifts a little it can still be fixed in post ¬processing, but if it shifts too much the artifacts will appear.
While shooting, you’ll not only need to lock down your camera; you’ll also need to lock your focus and aperture, so your focal point doesn’t shift. One easy way to do this is to first auto-focus your shot, then switch focus to manual and leave it. Lock down your ISO too, so your brightness levels don’t change when you shift exposures. Shoot at the lowest ISO setting possible, because HDR processing can introduce noise. Since your aperture and ISO settings are fixed, shoot multiple exposures by changing the shutter speed.
To get a complete HDR photograph, you’ll need to shoot enough exposures so that details in the darkest and lightest areas can be seen, but this could mean a large number of shots. A minimum of three exposures is recommended, one exposed for the mid-tones, one under-exposed and one over-exposed. The more exposures you have, the more detailed your final HDR photograph will be, so you can shoot any from three to ten exposures depending on the levels of brightness in a scene.
And always shoot in raw, which will give you more detail to work with than JPEGs.
To create HDR images, you need software which can process HDR images. The most popular program is Photomatix. Photoshop CSS ships with an improved HDR Pro feature which we’ll be using.
Creating HDR Photos
Now that you’ve shot your multiple exposures, it’s time to merge them into a single HDR photograph.
First, we’re going to open the files you want using Mini Bridge. Go to File > Browse in Mini Bridge. Using Mini Bridge, select the multiple exposures you’ve taken, right-click and choose Photoshop > Merge to HDR Pro.
Then, grab a cup of coffee. Depending on how many exposures you’ve chosen and how powerful your system is, the merging process may take some time. When the process is complete, you’ll see the Merge to HDR window, with controls and a composite photo representing your final HDR image. From here, you can choose from any of the custom presets or do your own adjustments. You’ll find a good selection of presets, from the popular and extremely stylized HDRI look to more realistic versions. Keep the Mode to 16 bit and Local Adaptation.
If you see strange artifacts appearing in your photo composite, check ‘Remove ghosts.’ These ‘ghosting’ artifacts usually appear because either your camera or something in your photo moved while you were shooting. After you check the ‘Remove ghosts’ box, Photoshop will select one of your exposures to use as the base photo for removing artifacts. You can also select the base photo yourself from the different exposures in the slideshow below to use as the ‘anti-ghosting’ reference. Try cycling through each to get the best-looking composite.
After you are done adjusting, simply click OK and you have your HDR image! Depending on how you’ve adjusted your image, you may want to do further adjustments in Photoshop. For example, a photo with all the details evident can look flat, so you can think about adjusting the curves even further to bring back the contrast and add pop to your HDR photo.