High Dynamic Range Software and Techniques

Digital cameras have a come a long way in the past ten years, and now a RAW file from a full frame camera can have a 12 stop exposure range. (Though it is in reality actually rather more difficult to extract the full range). There are many situations when this will not be enough, resulting in blown highlights and shadows dominated by noise. Combining several exposures in post processing will recover the highlight and shadow detail. In the early days of digital, this was little more than making an exposure for the sky, and another for the ground and merging them in Photoshop – often with mixed results.  The launch of HDR software like Photomatix and the features progressively added to Photoshop have made this somewhat easier – no need for masks or manual blending.  However, HDR has received bad press due to the unreal results that can be obtained with it.

Recently I have been carrying out an extensive test of Photomatix against various competitors that use the “Enfuse” open source algorithms to fuse multi-exposure images to give a more natural look than the classic “HDR”. This is partly due to frustration when using the Photomatix Lightroom plugin or standalone application at the difficulty of obtaining a natural image. I’m very impressed with the ease of use and the results from some of the Enfuse based systems. And the process of Enfusing also reduces noise – Tone mapping increases it. There is much less control than Photomatix, but as you will see, this seems to be an advantage in terms of the quality of output.

Before I start I should state that my interest here is to obtain a natural exposure – as close as possible to the original optimum exposure – but with the highlight and shadow detail from the lighter and darker exposures “added in” in a way that looks completely realistic. This would be like having a 24 stop exposure range on the camera. I am not interested in using “tone mapping” for creative effect.

The products I tested were

Photomatix – (From $39 to $119) http://www.hdrsoft.com/

The defacto HDR software, very comprehensive, and thus complicated – largely responsible for the popularity of HDR, but by the same token a number of awful images too! To see some awful over saturated unreal images, look at their website!

Bracketeer – ($30) http://www.pangeasoft.net/pano/bracketeer/

Mac only standalone application with brilliant user interface and comprehensive batch mode and the ability to align images (when not shot with tripod)

EnfuseGUI -(Donationware – donate what you like) http://software.bergmark.com/enfuseGUI

Mac or PC standalone application, basic interface with no alignment option

LR Enfuse – (Donationware – donate what you like) http://www.photographers-toolbox.com/products/lrenfuse.php

A Lightroom plugin with very slick integration into Lightroom, does align images.

It is worth pointing out some differences to the ways of working with the Enfuse products. For the Enfuse based products I left the settings at default values.

Bracketeer – in single image mode

Bracketeer. This Mac only application will work with RAW images, but it is recommended that you export images as TIFFs from your image editing application (eg. Lightroom for many) with the edits embedded, such as white balance fixed, chromatic aberrations removed, and highlights on the darkest image recovered if necessary. Adjust brightness and contrast of the brighter images. I found that highlight recovery of the dark image, and lightening the lightest image – particularly lightening shadows with fill light, lead to images that accurately matched the original, central exposure. The TIFF files can then be dragged and dropped onto the Bracketeer window for “enfusing”. There is also a batch processor, this can be pointed at a folder of images – as long as there are an equal number of images in the folder to combine – (eg. 3 exposures per image).  Alignment works well, but seriously slows down the whole process.

This has a very attractive interface and is very easy to use both for individual and batches of images. I did experience problems however with both version 3.4 (Leopard) and versions 4.2.1 (Snow Leopard). During batch processing they would often crash, and I’d have to remove the files that had been completed from the folder and restart the batch. This happened infrequently with 3.4, but the Snow Leopard version crashed after every third image had been Enfused. I was unable to resolve this.

Enfuse GUI

I was looking for a cross platform front end to Enfuse and came across EnfuseGUI. This has a rather clunky interface (obviously designed for the PC first!). Most importantly though it does not have an alignment capability, so this will only work with images taken on a tripod. I tried some that weren’t and they were unusable.

Limited use unless you always use a tripod, I did not include test images from this product below.

LREnfuse dialogue box, launched from within Lightroom

LR Enfuse

This works as a plugin for Lightroom, and the first advantage of this product is there is no need to separately export images as TIFF’s because Lightroom renders them ‘on the fly” for LREnfuse as required.  This makes enfusing images very fast and straightforward, and frankly once I’d tried this approach I was hooked. Alignment of images was good enabling use of exposures without the aid of a tripod. Batch processing is very intelligent. Group each individual set of exposures into a stacks, select and tick the batch processing check box on the LREnfuse dialogue box.

Photomatix

Photomatix has by far the most functionality of all the products on test, has the most control over settings, and has a very intelligent batch mode that can automatically recognise images taken within a short time of each other, and thus likely to be negatives for HDR’s. Photomatix also has multi processor capable support, making it very fast at zipping through large batches of images on multi-core machines.

Photomatix is mostly described in books and magazines in the “Local Enhancer” mode where a 32 Bit image is produced, and then “tone mapped” to get down to 16 Bits for further editing. However there is much more to Photomatix than that, as it has a batch mode that includes several exposure fusion options as well as two “tone mapping” approaches. It is possible to batch a folder of images, and choose all the different Photomatix options so that they are processed ready for you to compare, and choose your favourite. This is the technique I used for easy comparisons.

Photomatix “Batch Mode” dialogue box

Adjust = Photomatix exposure fusion 

Enhancer = Photomatix tone mapping with local detail enhancer

Compressor = Photomatix tone mapping with tone compression

I also tried the “Auto”, “Intensive” and “Average” settings but the results were not as good as the “Adjust” setting, so I have used this for the test. Photomatix recommends TIFF files that have zero settings on all the sliders in Lightroom, but with the right white balance set.

When processing images in batch mode with default settings, the results are sensible and give a good colour alignment to the original images.When processing individual images, in either “Enhancer” or “Compressor”, the default settings give crazy over saturated colours that bear little relation to the original images! I only used “Batch mode” for this test.

Photomatix tone mapping seems to exaggerate noise, with “enhancer” apparently worse than “compressor” exposure fusing reduces noise.

Photomatix also has a plugin for Lightroom, here is the dialogue for Exposure Fusion, which as you can see has a number of controls. This is far more intuitive than the “Enhancer” dialogue, for example the midtones adjustment does exactly what it suggests! Once these settings are established for one image, the same settings can be applied to a set of images in a batch.

Photomatix Exposure Fusion Dialogue box – note preview and histogram.

Comparison of images using various techniques.

First Image – Lloyds building, London, made from the three exposures at the top of this article.

Photomatix ENHANCER

Photomatix Compressor

Photomatix Exposure Fusion Adjust (defaults)

Bracketeer

LREnfuse

Observations from the first image.

Enfused images look virtually identical from Bracketeer and LREnfuse, and were sharper than all the Photomatix images.  Bracketeer, appears to desaturate blues, I was able to compensate for this in Lightroom after-wards, but it is rather odd. LREnfuse image was my favourite. Of the Photomatix options, “Enhancer” produces a low contrast, over saturated “glowing” look, “compressor” a much better contrasty natural look (with much darker shadows), tone compressor “adjust” produces an image very close in colour to the LREnfuse option, but not as sharp. n.b. All settings at default values.

Image 2 Classic Rolls Royces

Photomatix Enhancer

Photomatix “Tone mapping with detail enhancer” produces a glowing, soft, low contrast unreal image.

Photomatix Compressor

Photomatix “Tone mapping with tone compression” produces a much more realistic if dark image, with plenty of contrast. Th brightest part of the image is the left car radiatortop – all the detail is retained in both examples.

Photomatix Fusion Adjust set at defaults

Photomatix “Fusion adjust” produces a better image than either of the tone -mapped examples, with detail in shadows and highlights , good contrast and a natural look.

Bracketeer

Bracketeer produces an almost identical look to the Photomatix “Fusion adjust” setting, but the image is sharper.

LREnfuse

LR Enfuse produced a natural but rather dull image, but pressing Auto-Tone in Lightroom produced the image below.

LREnfuse post edited with brightness and contrast increases in Lightroom.

From the above comparisons, “fusing images” whether using Photomatix or the Enfuse based products, gives a more natural look to the images. It was noticeable how much sharper the “Enfused” images were.

Sharpness Comparison  Photomatix vs Enfuse

LREnfuse – note how much sharper it is – click for 100%

Photomatix Tone mapping with “Tone Compressor” – click for 100%

Conclusions.

“Exposure Fusion”  produces more natural results than “Tone Mapping”, Enfuse produces sharper images than Photomatix.

LREnfuse wins this test as it delivers natural looking images, straight from within Lightroom with the minimum of fuss. It simply meets my requirement without all of the complexity and unpredictability of Photomatix, which is of course a far more feature rich application. I simply don’t have time to much fiddle with a whole new set of sliders in Photomatix – I’d rather use Lighroom for that. LREnfuse does not require TIFFs to be generated and saved to a folder for later processing, making it quicker that Bracketeer.

Bracketeer works really well in single image mode – simple drag and drop, so if you don’t use Lightroom, and you are a Mac user, this is recommended for Leopard, but I got too frustrated with the Snow Leopard version which kept crashing in batch mode, which lead me to look around for alternatives.

If you want a natural extended dynamic range image with the minimum of fuss, choose LR Enfuse or Bracketeer. If you have lots of time on your hands then try Photomatix! The Photomatix plugin for Lightroom is very good, particularly in Exposure Fusion mode, and I much prefer this to the tone mapping options.

n.b. The Rolls Royce and Lloyds building were both taken with the Canon 5Dmk2 with Zeiss Distagon 21mm f2.8. The Bentley closeup crop is at 100% – if you click on it, and was taken on the Canon 24-105 f4L at 40mm

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