I’ve been getting lots of questions about HDR photography and how it’s done. So I thought I’d do a brief write-up about it here, and, more importantly, send you somewhere else. Sometimes others have already said it better. (To see some examples of my HDR photography, check out my tags on the side of this page, or go to my HDR portfolio.)
What is HDR? It stands for High Dynamic Range. An HDR photo has a much higher dynamic range than your average JPG. It has lots more image info in it. In fact, most computer screens won’t even display it right, since even they are not designed to show this much of a dynamic range.
The human eye has a pretty impressive range of brightness values it can see, from the blackest of blacks to the whitest of whites. Cameras have a much more limited ability to do this. That’s why when you take a picture of the sun, all detail in the brightest sections is lost. It’s just full-on bright white. Your eye does a much better job. (For those that care, the human eye can see a range of about 24 f-stops. A very good digital camera can only see about 11.)
How do we fix this with photos? We turn ordinary photos into HDR photos by taking multiple shots of the same scene. Most HDR shooters would say you need a minimum of 3 shots, all the way up to 9 shots, each one exposed slightly differently. My Nikon camera has a function called “exposure bracketing”. It’s a safety net that lets a photographer in a tricky lighting situation be sure that at least on the shots will look right. It lets me fire off three shots. The first is under-exposed (too dark), the second is properly exposed, and the third is over-exposed (too bright). If these shots are all shot without moving (ideally from a tripod), they can be combined in software to create a single HDR image.
A single HDR image does me very little good, since my computer can’t display it correctly, anyway. But there’s a program called Photomatix that’s great at doing the combining, and then letting me do what’s called “tone mapping”. This is where I get to turn my HDR image into a normal JPG. But I’ve got tons of sliders, adjustments, and choices to make to get me there. I can adjust all sorts of levels to get just the right look I’m wanting. While it’s usually a bit surreal (or hyper-real), the images often reflect what we remember a scene looking like.
Ever take a photo of an amazing vista, only to get home later, look at your picture, and realize you didn’t exactly capture it? It’s nothing like you remembered it! HDR photography seems to more reflect our memories of places.
The following photos show the exact same scene. One is the proper, middle exposure of three bracketed shots I did. This one, along with an over-exposed and an under-exposed shot, were combined to form an HDR image. The second image is the HDR image after it has been tone mapped and saved as a JPG.
A “normal” photograph.
A tonemapped HDR photo, made from the photo above it, plus two other photos.
The HDR process can be a pain to work with. The process can add lots of saturation to the colors. It an also add lots of noise to an image. It can crank up the contrast. And it can really make skies look funky (see the shot above, for instance). I almost always have to do some post-processing in Photoshop to get an image just right.
I’ve noticed that many people starting in HDR photography end up with atrocious results. Effects can be cranked way too high, in my opinion. Subtlety is likely better, unless the surrealism is an intended effect.Note too that thumbnails can look much worse than the full-screen versions of the pictures.
There’s a guy named Trey Ratcliff who is one of the best-known HDR photographers out there. I have his book, which is quite good. I also go to his website (StuckInCustoms.com) regularly. And he has a fabulous tutorial on HDR photography available here.