Best Free High Dynamic Range (HDR) Software

Imagine that you are inside a large Gothic cathedral, and the sunlight is streaming in from the windows. You pull out your digital camera and take a photograph of the beautiful artwork on the church wall near one of the windows. You needn't have bothered. Your digital photograph will be a flop. Either the painting will be dark and barely visible, or the window will appear as a glaring and dominant white area that is hardly recognizable as a window. Or both.

Digital photography is a wonderful technology, but it's not very good at handling scenes that are comprised of both very dark and very brightly-lit areas. The human eye is superb at this, but the sensors in digital cameras are not.

But, there is way to overcome this problem. It's called HDR photography, which works by combining several photos of the same scene, taken at different exposure settings, into one photo. The details of dark areas (from a longer-duration exposure) are combined with the details of brightly lit areas (from a shorter-duration exposure). The result is a single photo that is correctly exposed in both the dark and light areas. It not only looks like it is correctly exposed, it also looks more dimensional.

There is a related technique called tone mapping. Tone mapping is what tells the computer how to actually display this huge tonal range - and there are different ways to do it (different algorithms which have different parameters - this is what the scroll menus and sliders allow you to change). You can also tone-map a single photo, yet it will never provide you with a high dynamic range image by definition, it can only make low dynamic range scenes look like they were outputs of HDR processing. This can bring nice effects or make the image noisy and unnatural-looking. This being said, tone-mapping definetely can't be explained properly in a short paragraph, so if you're interested, there are lots of great articles on the internet for you to read.

To create HDR photographs you will need to do two things. First, it would be wise to use a tripod when you take your series of differently exposed photos (try 3 photos, -2EV, 0EV, +2EV), which will ensure that all of the photos are identically composed. Second, you need to combine the series of photos by using special HDR software. Taking the multiple shots may be easy, because most modern cameras have a "bracketing mode" that will allow you to automatically take a picture repeatedly at different exposures. However, if your camera doesn't have this feature, you can do it manually. Aperture priority will be best if you want to use exposure bracketing as mentioned above and manual mode and changing only shutter speed if you're taking each photo manually. Check HDR guides for detailed information and explanation.

There are several free HDR software packages, and I've had the opportunity to review most of them. Selecting the best was not easy.

Picturenaut

Picturenaut provides (all automatically) image alignment, exposure correction, color balancing, noise level compensation, and derivation of the camera curve from the source images.

It supports most formats, including PFM (Portable Float Map), HDR (Radiance), EXR (OpenEXR), TIFF (32-bit Floating Point), TIFF (LogLuv), LDR, JPEG, TIFF (only RGB color space), TGA (Targa, no alpha channel). It has now the ability to process RAW files. I have checked this out using my NEF RAW files and it worked like a dream.

Simply explained, weighting defines the values between dark pixels and light pixels. Dark pixels have noise in them and light pixels are usually over-exposed. Instead of dropping these pixels, they are assigned a weight value. Depending on your image, the weight function may help you obtain a better result. The EV (Exposure Value) can be taken from the EXIF information attached to the image, or assigned a manual value (this is excellent for cheating HDR's). As a modular piece of software, its most important functions can all be accessed from a command line. The downside is that you cannot alter the alignment of the image manually, but I have done tests on auto alignments and Picturenaut came out the best.  If you are looking for straightforward images without excessive tone mapping this has to be your top software.

FDRTools Basic

FDRTools Basic is a solid piece of software, appropriate for those looking for a fast and efficient way to incorporate more dynamic range into an image without the risk of getting a fancy-looking, halo-happy, and tonal hierarchy deprived output.

The supported import image formats are: JPEG, TIFF, Radiance RGBE, OpenEXR, Integrated RAW converter plus DCRAW for direct import of virtually all digital camera RAW formats. The supported export image formats are: Radiance RGBE, OpenEXR, TIFF, PNG, PPM, BMP and JPEG.

There are four windows that you can view: display of menu with images and adjustments, preview area, progress and navigator. When you choose to align the images, the application automatically compensates for any 'slight' camera wobble. Once the images are aligned, you may manually adjust to create a slight misalignment for image creativity (sometimes a slight misalignment can create a better HDR image by giving it more depth).

It provides two tone-mapping options: 'Simplex' – adjusting histogram, gamma and saturation,  and 'Receptor', which has two more sliders: 'compression' and 'brightness', which, set to their default values, do change the look of the tone-mapped image. So you will want to switch between the two and see which one you prefer. I believe you should always use Receptor, as it not only gives you more artistic freedom, but also yields better results with the default settings.

What are you going to get? Most likely a noticeably range-expanded photo without sharpness loss, with pleasant colors, although you may find that the sky looks a little flat or 'burns' some fine detail like in a photo with overexposed sky. Also, the output could use more local contrast, as the images tend to have a slight, I would say, 'plastic' feel to them. I would say they are on the realistic yet needing enhancement side.

Please delve into the 'Preferences', as this will acquaint you with the settings, allow you to specify your own final-image format, and select a destination file for your finished images. Worth checking.

Essential HDR Community Edition

Essential HDR Community Edition is a fantastic free HDR software that blows the others out of the water when it comes to tone mapping.  Their goal is to better Photomatix, which has made itself the bench mark of HDR software.  It has an easy interface that allows you to manipulate the image by tone mapping, histogram and color balance.  The best way to get a good result really is by using a tripod, however, it does have the ability for alignment if you have hand-held the photograph.  Don't hold your breath here, I have found it's not that brilliant.  Yes it is FREE, but the limitations of this software allows a maximum image size of 1 MB.

To give you an example I took 3 images on different EV values 2592 x 1944 px (5 MP, 4:3).  After combing the images the results were:
.tiff gave me a size 858 x 647 px – 2,187.9 KB
.jpg gave me a size 858 x 647 px – 842.9 KB

Obviously to get the most out of it is to save as TIFF, it's enough for use on the internet or a decent A5 image.  For this reason its not my top choice.  You also have to remove the small watermark at the bottom of the image, not a lot to spoil it.

Result image can be saved in the following formats: Jpeg, BMP, PNG (8-bit RGB), TIFF (8-bit and 16-bit linear RGB), Radiance HDR.

Source image can be in the following formats: Jpeg, BMP, GIF (8-bit  RGB), PNG (8-bit RGB), TIFF (16-bit linear RGB), Canon Raw file (CRW and CR2), Nikon Raw file (NEF), Pentax Raw file (PEF), Sony-Minolta Raw file (ARW and MRW), Adobe DNG, Radiance HDR, OpenEXR

Luminance HDR (Qtpfsgui)

Luminance HDR is the best option if you want to experiment. Nine different tone-mapping algorithms, that means - if you want 'that' particular HDR look - there's a fair chance you'll achieve it with Luminance HDR. More realistic? Sure. A little like a drawing? Sure. Maybe surrealistic? It's all here. 

Although I consider Luminance HDR a top-notch free HDR product, there are a couple of things that can deter the potential user. First of all, the interface isn't too user-friendly, so it may take you a while to feel at home working with Luminance HDR.  For instance, to see how new parameters that you've set affect the image, you have to click a button. There's no 'real-time' preview. On the other hand, Luminance HDR easily creates new tabs (just like a browser) with rendered results. It's never been easier to compare the results that dfferent settings produce, without having to 'try hard' to remember how it looks now, then move a slider or two, and think hard if it looks better or worse.

I would say, if you enjoy playing with HDR, if you want to explore, if you feel your current HDR program doesn't let you achieve the results you want, try Luminance HDR. It will be an adventure.

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HDR photography, HDR photo, high dynamic range software, HDR freeware, HDR free software.