I’m sure you’ve seen HDR photography before – usually in that whacky surreal style that looks more cartoon than photograph. HDR (or High Dynamic Range) photography can also be used in a much more subtle way to solve on of the biggest problems photographers have – the fact that your camera can’t capture the range of light and shadow that your eyes can in one shot. The dynamic range (from brightest to darkest area) that a camera can handle per picture is significantly less than you can see, but with HDR photography, you can take several pictures that capture different elements of the same image and put them together later. Hit the jump for more info.
HDR photography was popularized by a program called Photomatix from a company called HDRSoft. It’s a good program and all, but it specializes in creating images that are a little over the top. Photoshop, starting with CS2, has a pretty good HDR capability built in, and that is what I use. First, however, you need your source images. Generally speaking you want at least three, but you can use 5 or more as well. In order to do this with relative ease, you’ll want a camera that has an AEB mode (Auto Exposure Bracketing), as most DSLRs do. On my Canon I turn on AEB and then set it to the maximum range, which is -2, 0, and +2 stops. This means that when I take three pictures in a row, the first will be regularly exposed, the second will be 2 stops underexposed and the third will be two stops overexposed. Make sure you take the pictures in Av mode, as you want the aperture to stay the same throughout – remember: you’re going for three pictures that are identical except for the exposure level.
Another thing to think about is that you’ll want these pictures to be as similar as possible. Moving subjects are going to be a problem. Subtle movements (ripples on water, for example) might be ok, but this might not be the best techniqe for capturing speeding cars, toddlers, etc. You’ll want to keep the camera as still as possible – tripods are the best, railings to brace on are ok, or a good camera strap pulled tight will work if you’ve got everything else in order. The HDR above was shot with just my handy R-Strap. Lastly, you’ll want to active burst mode, so that you can take the pictures faster and easier. That means all I’ve got to do is get my settings right and hold down the shutter button until it fires three times. I know it sounds like a lot of settings and configuration but once you’ve done it once or twice, it’s pretty darn simple. I can go from shooting regular shots to shooting the three source pictures I need for an HDR in about 5 seconds.
Alright – now you’ve got your pictures! You should have something like this:
Open all three files in Photoshop, and then select File -> Automate -> Merge To HDR… Click the Add Open Files button, and ensure the Attempt to Automatically Align Source Images box is checked. Watch your computer churn for a little while and then what you’ll have is your rough image! Just a little fiddling to go. Move the White Point slider until you’re happy and press Ok. Now we have an image, but we’ve got one problem – it’s got so much depth (32 bits) that we can’t do much with it – a JPG can only handle 8 bits of depth, for example, and that’s probably where we’re going, right? Right? Select Image -> Mode -> 8 Bits / Channel… Slide the Gamma slider around until you’re happy and then the Exposure slider until things look right(ish). Click Ok and you’re real close! Now all you have to do is whatever you usually do – for me that probably involves some curves, sharpening, whatever. Are you proud of yourself? You should have an image with more detail in both the highlights and the shadow areas than in any of your source images. This of course works best when you start with a scene that plays to the strengths of HDR. A room with both bright lighting in parts and shadows in others. A sunset. Bright sun sillouetting an ancient Thai temple – something like that. Oh yeah – one more caveat: there are a million ways you can get to the final product, even within Photoshop. I’ve just listed what I do. Play around – if I can figure it out, the bar can’t be that high.