Umesh Bhatt

Let me start by saying that I normally dont write reviews. In some ways, I feel one shouldn’t be constrained with the choie of tools, but to rather use all available tools as required to generate your final image.

So, Why did I write this review? Simply because – after using the software on a few images, I felt the same way when I switched to using Capture One from Lightroom. The software finally does justice to the images that is fed to it.

OK – Lets get started. First a disclaimer: I don’t have a lot of experience with this product. It is still very new in the market and I haven’t run as may images through it as I have with Photomatix, so technically speaking – this is not really a review. A detailed review is available in the references below. This is more of a summary/highlights on how I feel about using this product right now, and handles specific topics that are of interest to me – example: comparison with Photomatix, Its unique features/qualities etc…

HDR Expose is a product from Unified Color. While this product is not new (It replaces an earlier product called HDR Photostudio) – the user interface and enhancements to its functionality makes this product very usable as compared to its predecessor. See the reference links for a review on this earlier version of the product.

One of the biggest differences between HDR Expose and the other HDR processors is its use of a unique and proprietary color space called Beyond RGB (see references below).  As per a document found on their website, Beyond RGB is similar to the Lab color model (which represents the human visible spectrum: see references) but is tweaked to work for higher dynamic range (see note 1 below) and represents each color value in terms of brightness, chroma and hue (which again, is the same as  Lab color model).  Since this color model allows separation of the brightness/luminance from its color (chroma & hue) information, one can manipulate the highlights/shadows,contrast and dynamic range of the image while color accuracy is maintained. This is a huge advantage as compared to all other HDR software out there (which uses RGB model and there is an impact to the color rendition/hues of the images as it is processed/tone-mapped).

In the example below, I have compared conversion of the same scene using 3 different HDR processors. The first thing to notice is the color variations between the 3 – of course, it is perfectly possible to tweak all 3 editors to match each other, but that is not the point. All 3 converters had custom white balance on the bottom window sill .

A custom white balance inside the house will render the inside/indoors with a sunny white balance, but will make the outdoors too blue, while a white balance dropper on the outdoor scene will render the indoors too yellow. Here is a corrected image from HDR Expose:

• Conclusions (for this image conversion):
  • Enfuse conversion produced an image that has the best overall white balance and natural colors and look to it. No further tweaking required.
  • Photmatix converter produced an image that has the most details extracted both indoors as well outdoors through the window.
  • HDR Expose has the best overall natural rendition of indoors while retaining most of the outdoor details. There was no blooming of colors and notice the natural smooth color tonality near the chair (area circled in image strip) – this is actually from a 2^nd tungsten lamp out of frame. Also notice the warm glow on the pillow below from the lamp closest to the viewer on the top right corner. This scene is a pretty complicated scene with multiple color temperatures both indoors and outside – and I was able to render the scene pretty accurately with this software.

• Some of the other features that I found worthy of interest/mention are:
  • The reduce halo artifacts: finally – a button that works!
  • Dynamic range mapping: ability to map and retain a selective dynamic range from its extended dynamic range – controls the HDR to LDR conversion characteristics - somewhat like a photoshop curve actually
  • Shadow/Highlight/Brightness/Contrast: These four controls are the global and local operators and control what and how the details are extracted.

04Aug2010: Updates based on my experience thus far:

As I have continue to use the product – I seem myself going back to this software to see how they handle my images.

• I generally find that when I launch HDR Expose from within LR3 to merge a series of images, It pretty much locks up my Core i7 2.8 Ghz, 8GB iMac. I found the CPU pretty much pegged at 100% for the duration of the merging process. This is such a shame especially considering – I have never had this issue on any application. I found that I cannot use my mac at all – even the Cmd+Tab was inoperative.
• In my general opinion – the Dynamic Range Mapping tool is very limited in its usage. Ideally speaking – I would have loved the option to directly work on the histogram – pushing and pulling the edges or moving the window to indicate which part of the dynamic range I wish to tone-map. In the current approach, the “average” dropper is pretty much a “hit” or “miss” approach. Neither technical nor artistic in my opinion.
• I found found that I have been only using 3 controls of all the ones available – The Dynamic Range Mapping with a hit or miss method, Shadow/Highlight & Brightness/Contrast.  The White balance functionality while pretty decent – is not extraordinary, and yields incorrect results in mixed lighting conditions unless you shot a gray target earlier and know the exact kelvin temperature.
• While the tool is really excellent for obtaining accurate colors, it is quite unsuitable for artistic purposes. For example – the grunge effects, or hyper contrasty skies or super saturated trees….etc. I find that this software will be very valuable for architecture and interiors. So – that pretty much means that Photomatix is not its competitor - Enfuse is.
• Based on my preliminary tests – HDR Expose is certainly a better tool compared to Enfuse. However – Enfuse is free to almost free.

Note 1: The color gamut of this color model is supposedly so huge, that it can address a dynamic range of 10⁷⁶. That is a bigger gamut than what most people need or want. As an example – the dynamic range of a bright outdoor scene in bright sunlight with shadows is about 100,000: 1 (10⁵).

References:

1. http://www.unifiedcolor.com/download/Unified_Color_Beyond_RGB_Model.pdf
2. http://hdrphotostudio.com/download/Unified_Color_BEF_format.pdf
3. http://www.openexr.com/TechnicalIntroduction.pdf
4. http://www.tkrphoto.com/2010/07/hdr-expose-review/
5. http://www.dpreview.com/news/1007/10070602hdrexposediscussed.asp
6. http://www.adobe.com/digitalimag/pdfs/color_managed_raw_workflow.pdf
7. http://www.outbackphoto.com/CONTENT_2007_01/section_hdr_and_tonemapping_2009/20100211_HDRPhotoStudio/index.html