Registered: Nov 12, 2002
Total Posts: 11230
Country: United States
People often point out limited dynamic range as one of digital photography’s shortcomings. True enough. However, at least in the world of landscape photography, that claim is becoming less and less true, mostly thanks to HDR (high dynamic range) imaging. In this tutorial I will show, by example, my method for creating an HDR image. I will be using Photoshop CS3 Beta. However, all the steps are also available in PS CS2. I have no experience with other HDR creating software such as Photomatrix, so I won’t be able to comment on them.
Here’s the most important rule to remember about HDR photography: The higher the number of bracketed exposures, the better the outcome. I almost always use at least 6 exposures, and in this example, I’ll be using 9 bracketed exposures, each 1 stop apart (from -4 to +4 exposure units). I also highly recommend that you not increase your bracket width beyond 1 stop. For example, if you want to bracket -2 to +2, expose in one step exposure increments (-2, -1, 0, …). Don’t do -2, 0, +2. Armed with these two important “rules,” you’re ready to tackle HDR photography.
As with any type of photography that involves blending exposures, a steady tripod is a must. Cable release and mirror lockup are highly recommended. Let’s begin!
In Adobe Bridge, I selected 9 bracketed exposures and chose Tools ? Photoshop ? Photomerge… The following is the resultant screen:
To give you an idea of the dynamic range available on the above image, I’ll show you the resultant image after moving the histogram slider to opposite ends:
As you see, the available dynamic range is nothing short of amazing!
Now here’s the image I decided to create. As you can see, I’ve sacrificed the sky detail for the sake of FG detail. It doesn’t really matter how you convert. I just chose this at random.
The product is a 32 bit photograph. Of course our monitors aren’t good enough to show all that info. Therefore, we now have to convert this image to 16 bit. In PS, choose Image ? Mode ? 16 bit. A dialog box appears, asking you how to convert the image. In my experience, the best method is Local Adaptation. Choose this option and then show the histogram:
On the histogram, I suggest clicking on the line at regularly spaced intervals as below, to have finer control of your curve:
Now to tackle the radius and threshold options. For radius I like to use between 75 and 150. For threshold, I like to use between 1 and 2. The values depend on the image, but these ranges have worked for more than 95% of my HDR images. If I choose a threshold value less than 1, I tend to get “haloing” around high contrast interfaces. Above 2, the image appears too low in contrast. For this image, I used radius of 100 and threshold of 1.87. Next is the most difficult step, in my opinion. This is where you need a lot of patience and practice…adjusting the curve. An advice I have is that you not make any abrupt transitions between points…let the shape of the curve be gentle. Also, remember that, in general, the left side of the histogram controls the dark areas and the right side controls the bright areas. Here’s my curve and resultant image:
The above image is not bad, but it lacks punch (contrast). To correct this, I simply apply a curves and a levels adjustment layes as below. Please note that I applied a gradient mask to the levels to darken the sky but leave the FG unaffected. I also did a tad bit of burning to a few of the clouds.
Here is the final image and my history palette, showing all the steps. The FG isn’t as bright as it could be (and that was intentional), but the slight darkness gives it a more “natural” look, I think.
Now for those that have cameras that can only bracket 3 exposures what do you suggest?
