It all happens in the software, so choose wisely
High Dynamic Range (HDR) software tries to solve an age-old photographic problem of how to capture a full tonal range when the contrast exceeds the capabilities of your sensor.
In this article I’m going to describe the process merging the same set of images into a single HDR image using Adobe Photoshop CS5’s built-in HDR Pro and Photomatix, a standalone program with plug-ins for Apple Aperture as well as Adobe Lightroom and Photoshop. Photomatix, from www.hdrsoft.com is probably the best-known HDR software, and one of the best.
Merged HDR images can look horribly cartoon-like but I’m going to try to keep the result believable if not completely natural looking.
My starting point is a series of nine Raws shot at 0.5EV steps from -2 stops to +2 stops keeping the aperture the same so the depth-of-field is constant. HDR processing takes the full dynamic range of the set of shots and represents this in a 32-bit file. As screens and printers can’t reproduce such a wide tonal range, you then map these tones to a 16-bit file which can be displayed. It’s the choices made in the mapping.
Using different HDR software to achieve the same result from a single set of images is an interesting exercise that is always worth trying.
In comparison with the HDR facilities in previous versions of Photoshop, CS5’s HDR Pro is a huge advance. It gives more control over the results and is faster. The controls in Photomatix, while on the surface more complex, made it easier to get the results I wanted. Although the preview update was noticeably slower, the instant help on the controls and 100 per cent loupe viewer are great and it is a top software for this sort of imagery.
photomatix pro step-by-step
HDRsoft’s Photomatix Pro is the best known – and probably the best in terms of performance – HDR processor on the market. Now in its fourth release it manages to combine powerful tools with handling ease.
The workflow when creating an HDR image using Photomatix differs from using Photoshop CS5’s HDR Pro in a significant way.
Using HDR Pro allows you to use Adobe’s sophisticated Adobe Camera Raw (ACR) Raw file converter without converting to a 16-bit TIFF file along the way. This preserves the maximum exposure data for use in the HDR conversion.
HDRsoft includes a Raw converter but describe this as ‘slower and of lower quality’, so its recommended workflow is to convert to a 16-bit TIFF file using your choice of Raw processor, then load these images into Photomatix for HDR processing. In theory some quality is lost but this is minimal and in practice this is hard to see.
HDRsoft has plug-ins to integrate Photomatix with Apple Aperture, Adobe Photoshop and Lightroom making the conversion more convenient. It just helps workflow and can save time.
For this article I’m using the Lightroom plug-in. However, the standalone version has the same interface. The interface layout is clean so finding your way around is pretty straightforward.
I’m going to aim for a more natural-looking HDR result when I process the files, but I’m also going to try a slightly more extreme but still tasteful conversion, as a comparison.
Bring in the images
Having tidied up the images in Adobe Camera Raw, Lightroom reads the corrections and I don’t need to repeat them. I did check that the develop settings were all set to zero – for example the Black defaults to +5. Then select the images and click File>Export>Photomatix Pro. In the dialogue box I accepted the defaults.
A preview appears allowing you to specify areas of the image that may have ghosting. In this image the clouds may have moved slightly between exposures so just draw around the sky, right-click and select Mark selection as ghosted area. Photomatix will choose a source image but from the same menu, you can make your own choice.
Process the image
Photomatix next displays the 32-bit HDR image. As the image’s dynamic range is a lot higher than current screens can display, the result looks poor. To process the image to a 16-bit image which can be displayed or printed, click on the Tone Mapping/Fusion button. This gives access to the adjustment tools and a set of thumbnail presets along the bottom.
Take your pick
You can choose from Exposure Fusion which combines your exposures, taking pixels from the best exposed parts of each image or Tone Mapping which uses HDR processing to map the 32-bit file to a 16-bit output. This is what I’ll be using. Trying out the different presets I found Enhancer-Smooth gave a really good starting point.
Control the highlights
The blown-out area surrounding the sun is rather large. Using the selection mode draw a loose circle around it, on the right-click menu replace this area with any of the source images. I chose the -2EV version and the blown-out area is reduced. You can also disguise the lens flare on the rocks by replacing the area with the -1EV image.
Adjust the various sliders by small amounts to fine-tune the effect. Photomatix displays useful help at the bottom left as you move the mouse over each control so you can understand what you’re adjusting. I added some highlight smoothing and micro-smoothing to reduce the grey area around the intense sun. Click Save and Re-import and the TIFF file is returned to Lightroom. That’s the Natural image below.
Now let’s push the boundaries further and process the same files with a bit more of the HDR look. Selecting the Enhancer-Grunge preset is a start but too saturated for my tastes and the sky is very grainy. I started by warming the image up using the Temperature slider and chose the Medium lighting effect. This combined with a reduction in gamma and saturation gives a brooding look. The finished image is below.
I don’t like the noise that’s appeared in the sky. The Micro-smoothing control has let me reduce this a little without softening the whole image. After some time adjusting and re-adjusting the overall Saturation and the Highlights and Shadows values I ended up with a natural-ish image and a more extreme image – exactly what I was looking for. As with all HDR images, though, your views may differ.
Photoshop CS5 HDR pro step-by-step
With version CS5 Photoshop received a major update to its HDR capabilities. HDR Pro gives more control and is substantially faster than previously.
For this landscape I’ve used the controls to try to achieve a natural look without the more extreme effects that HDR is known for. The challenge was to bring out the shadow detail in this contrasty scene while retaining the sky detail.
You can use JPEGs for HDR but it makes more sense to start with Raw files as they contain a greater tonal range. Use Adobe Camera Raw (ACR) to make global corrections before starting. In this case the horizon was off kilter and there were a few dust spots to remove. In ACR you can make these corrections to one image and copy them to the rest.
Even though there are only a few sliders to work with, they do interact substantially and I found myself constantly moving between controls, making small adjustments to each and watching the effect. If you’re new to HDR editing, start by playing with each individual slider pushing it to the extremes to gain an idea of the effect then gradually home in on your final settings. The preview window updates in real time helping enormously when making your final tweaks.
It’s important to get your adjustments right as, once you continue with the blending process, you can’t go back and change the settings. As a precaution, save your settings as a preset, then you can always start again, apply your preset and make any changes from there.
Tidy up the images
Before creating the HDR image there are a couple of edits to apply to each image. Selecting all nine images then right-clicking on one opens them in Adobe Camera Raw. Drawing along the horizon using the straighten tool sorts a slight tilt and removing sensor dust spots with the Spot Removal tool completes the clean up.
Apply the changes
Click the Synchronise button to apply the changes to all the images, click Done to leave ACR. Click Tools>Photoshop>Merge to HDR Pro. The HDR dialogue features a large preview and controls to fine-tune the image. Adobe provides presets as a start point but they didn’t really work with this image; this is Photorealistic High Contrast.
Avoid the halos
Start by adjusting the Radius and Strength. In this contrasty image smaller values are needed otherwise you begin to get white halos around the cliff edges as you can see here. The controls interact with each other so you need to spend time making small adjustments of each one until you get the effect you want.
Moving to the Tone and Detail panel. Adjust the Gamma to set the contrast. Adding too much Gamma to this image gives a grey centre to the sun, which is not a good look. Reducing the Gamma helps, but as the darkest shot still has a blown-out sun, I decided to look for the best overall Gamma and try to adjust the sun later.
The image is slowly improving so try the Detail slider next. This acts similarly to sharpening so needs using with caution. I’ve started at 300% which as you can see is far too much and gradually moved down to 124% as a good compromise. Adjusting the brightness upwards and balancing this with small Gamma edits has improved the sun.
Clicking the Remove ghosts box removes any ghosted areas caused by movement between exposures such as the clouds. You can change the image that CS5 has chosen and for this image it also seems to reduce the banding around the sun. The darkest image works best. A final slight boost to the shadows using the tone curve and we’re finished.
Taken from the April 2012 issue of Advanced Photographer magazine