The dynamic range your digital camera is capable of capturing is limited in comparison to what the human eye can see. The actual spread of tones individual models can record successfully varies, but if you’re photographing a particularly high contrast situation – eg, a scene with a bright sky and a dark foreground – chances are, it’s going to struggle.
There are a few ways to get around this: one is to use a neutral density graduated filter (ND Grad) to stop down the sky and lengthen the exposure, helping to expose both the dark and light areas correctly.
If the ND Grad filter isn’t an option, however, then shooting two or more images with different exposures – exposing for the bright and dark areas individually, then combining them post-shoot – is an alternative method for obtaining a correctly exposed final image. This is the route we’ll be exploring in this tutorial.
The act of combining different exposures of the same scene is referred to as high dynamic range imaging (HDRI). Although often associated with a highly processed, hyperreal look, HDR images can be more subtle too, depending on your personal preferences and level of processing skill.
This tutorial will reveal how to shoot a series of bracketed images taken at different exposures, then combine them using Photoshop CS5’s brand new HDR tools. You’ll need a digital camera with manual exposure controls, a tripod and Photoshop – preferably CS5.
Although not essential, shooting with your camera on a tripod will make it easier to merge shots later on, as shooting handheld can lead to changes in your composition between shots, resulting in ‘ghosting’ in the HDR image. We took our images handheld, but took steps to minimise the risk of compositional alterations between shots (see Step 7).
The exact settings you need to use will vary according to the lighting conditions and your subject, however – as a general rule – it’s a good idea to keep the ISO low (100-200) to combat digital noise. For landscapes, aim for a narrow aperture (large number) to keep as much of the scene in focus as possible. Around f16-22 should do the trick.
If your camera allows it, shoot RAW files wherever possible to ensure you maximise the dynamic range captured in each of your images. RAW files contain more data about the scene you’re capturing than compressed JPEGs do, so it makes sense to start with the maximum amount of detail possible. If you can’t shoot RAW, ensure your camera is set to record the highest amount of detail it can in the image settings.
You need to find the right settings to produce the correct exposure. Shooting in Manual mode means you can control the shutter speed, just make sure the aperture stays the same for each shot. Meter the scene and adjust the shutter speed until you get an even exposure. Once you have a balanced shot, use your camera’s Bracketing feature to take at least one shot a stop or two above and/or below this middle exposure.
The exact process involved with setting your camera to bracket your shots will depend on your particular model, but DSLRs, most superzooms and some compacts will allow you to do this, using Bracketing/Exposure Compensation. Ideally, you’ll need to shoot at least two bracketed shots to create a merged HDR image. For this tutorial however, we’ll be shooting five shots.
A lot of cameras will offer an Auto Bracketing feature, which can really help if you’re trying this technique. Typically, you have the option of setting the camera to bracket at least three shots (some allow you to do more), a predetermined number of stops apart. We set our camera to shoot five images in succession, one-stop apart, to capture a wide range of tones.
As previously mentioned, if you’re not shooting with your camera on a tripod – or if there’s a lot of movement in your scene, for example, people in a crowded street – it’s particularly important to minimise the differences between each of your frames to make it easier to compile them in Photoshop. To help, set your camera to Burst mode (Continuous shooting) and it’ll take your bracketed sequence of images in quick succession.
With your shots in the bag, it’s time to fire up CS5. If you have an earlier version of Photoshop, you can still use the older Merge to HDR feature, but you won’t have access to all of the tools used from this point forward. Upload your images using your usual method and place them in a folder ready to be merged.
In CS5, under the File>Automate menu, you’ll find the brand new Merge to HDR Pro option. Clicking it – as with previous versions – calls up a dialog box that asks you where you want to source your sequence of images from. Hold down to select your multiple files, then click OK to start the process.
You can sit back for a few moments while CS5 goes to work, before the new Merge to HDR Pro interface appears. A preview of the final shot takes precedence, with smaller thumbnails showing your source files below. You have the option of activating/deactivating any of these source images, by clicking on each thumbnail in turn. Note that deactivating an image removes it from the final merged shot.
The right-hand side of the interface incorporates nine sliders and a drop-down menu, which let you manipulate the look of your final shot. You can also choose between 32-bit, 16-bit and 8-bit processing and click the Curve tab to view the histogram and make further alterations.
The Preset drop-down menu contains a number of pre-programmed options that you can choose from, to use as they come, or to utilise as a starting point, which can be tweaked further using the sliders. We chose to create our final shot from scratch, creating a Custom setting which can be saved for later use if you wish.
Sometimes when things move a little between shots, you get some ghosting (fast-moving clouds, people in a street scene or – in this case – wind blowing the trees). CS5 offers a Remove Ghosts tool to combat this; tick the Remove Ghosts option, wait a couple of seconds, and – as if by magic – the ghosts are gone! If your lens suffers from chromatic aberration in brighter exposures, pick one of the darker shots to take precedence beforehand.
Now we have a basic starting point for our HDR image, we can begin tone mapping: really fine-tuning how our image looks. Start by playing around with the various sliders, getting a feel for what each one does. Keep the Radius fairly low as it will introduce halos and some unsightly effects, even if you do have a penchant for the more stylised HDR look!
We’re pretty pleased with the overall exposure of the image – it’s a little underexposed overall, but this complements the mood of the shot. The amount of work you do from here depends on whether you favour a highly stylised look or a more subtle, photorealistic result – in this instance, we favour the latter.
Boost the clarity of the detail in the image by pulling the Detail slider to the right. If you go too far, it’ll start to break up so don’t overdo it. Move the Shadow slider to the left to inject more contrast. Move the Highlight slider to the left by about -15%. Note how this recovers the blown-out highlight from the top left corner.
Finally, inject a bit of colour back into the shot by shifting the Vibrance and Saturation sliders to the right. We opted for values of around 30% respectively, but adapt these settings to suit your own taste. As a side note: for images with skin tones in them, the Vibrance slider will affect everything but the skin tones, whereas the Saturation slider will enhance everything universally. Once happy with the result, click OK to return to Photoshop.
If you feel the image needs a little more honing, obviously CS5 has a whole host of tools to help you do just that. To finish our image, we simply applied a little Unsharp Mask – set to 50% – before saving our final composition as a TIFF.