How to Create an HDR Photo

The photography world is buzzing nowadays with the latest technique in creating perfect exposures every time - the High Dynamic Range (or HDR) photo. Using a series of images ranging from underexposed to overexposed, a perfect image can be blended together using Adobe Photoshop CS2 or CS3, assuming you've got the right equipment and follow the procedure accordingly. It may be a bit daunting at first, but it can quickly become second nature.

The first thing you'll need is, of course, a camera. But not just any camera will suffice. In this case a Digital SLR camera, such as a Canon Digital Rebel XTI or 5D, is recommended to take advantage of multiple shutter speeds. If you have a point-and-shoot camera that will allow you to manually adjust both shutter speeds and aperture, that will work as well. If you've never worked in M mode, or changed around those settings much, you'll learn how here.

Next you'll need a tripod. This unfortunately isn't optional because the images that Photoshop merges all have to be identical and can not have shifted at all. No matter how steady your hands are, they will produce shaking and none of them will line up.

Another piece of equipment you may want to consider using is a shutter-release cable to prevent camera shake when the shutter button is pressed. It seems like a lot, but it's worth it.

Onto the technique! A good practice subject is a sunset because they're readily available and that will also show you the true power of an HDR photo. Find a scenic spot so that you can see the sun on its way down and set your camera into M mode. You could technically use Tv mode, which allows you to control just the shutter speed, but we'll stick with M mode just to make sure the aperture also remains constant. Most cameras have a small light meter built into them and will tell you if your exposure is potentially over or underexposed. Using this meter, move your shutter speed down so that the meter is at the -2 and take your first shot.

Now that you've got one, just how many photos do you actually need to create a good HDR photo? Technically Photoshop only needs three to work, but ideally you'll want between 10 and 15. Why so many? This gives Photoshop a larger range of values to work with when blending between lights and darks, and thus, creating a smoother transition and more aesthetically appealing photo. So with your first photo captured, increase the shutter speed a bit and take a series of 10-15 photos gradually increasing the shutter speed for each one until you're at the +2. The photography part is done! Now pack up and head back to your computer to see your new HDR image.

Using Adobe Bridge (bundled with Adobe Photoshop), select all of the photos you took for the image and go up to Tools -> Photoshop -> Merge to HDR. Photoshop will begin working and at this point, you wait. In fact, no matter how fast of a computer you have, this process will take a while. Go make a sandwich. Actually you'll also have time to eat the sandwich. You know what? You'll even have time to clean up the dishes after you eat your sandwich. How bout a drink?

Well if you're computer is relatively new, it should be close to done by now. You'll know when it's done because it will present you with a dialog box verifying which images you want to use, all of them checked by default. In most cases you'll want to hit OK and proceed.

Now you're left with an image that doesn't look so great. It's ok though, all information is stored in there in much deeper levels than you're used to working with as 32bits per channel. In order to clean it up and create the photo you were wanting, you'll first have to convert it to 16bits per channel. This can be done by going up to Image -> Mode -> 16bits/channel. This will open up another dialog box with four options in a drop-down menu. 99% of the time you won't have to worry about the first three. Instead, select the fourth one and then click the arrows at the bottom-left to expand the window. After doing this you'll notice that your image looks even worse now behind the Curves window that was just expanded. At this point it's just a basic Curves window and if you have experience with curves, you probably know what to do here. If you don't, or you need a bit more explanation, the bottom-left area controls the shadows and the top-right area controls the highlights. You'll notice a histogram behind the curve (at this point a diagonal line). Drag the bottom-left point to line up with the very edge of that histogram and you'll notice the shadows in the photo become more pronounced. Do the same with the top-right point and you'll notice the same happening to the highlights. Be careful not to overexpose each though.

Now it's almost ready to go. This final step though can be a bit tricky and certainly takes practice. The great thing about Curves is that you can add a point anywhere on the line and drag it to bring out more highlights or shadows or midtones. It takes a bit of playing around with and since every photo is different, there's no magic formula. The thing to remember though is that you want your curve, ironically, to be as straight as possible. You still want to create bends though because that will create contrast, but just don't get too excited with them as that can create unwanted effects.

Give it a little practice. Now that you know the technique, you're able to do it all you want! Also don't be afraid to try it on things other than sunsets, some interesting effects can be found by using this technique on night shots, water, skies, etc.