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. HDR photography 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. I won't attempt to explain this, but you can read more about that here. I'm also aware that the newer concept is to tone map just a single image, and most of the available HDR software will allow you to do this.
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, 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. In the future that software may be built into digital cameras, but it isn't at this time, although the newly released Panasonic DMC-TZ5 [6] comes close.
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 "automatic" feature, you can do it manually. Check your camera's guidebook.
There are several free HDR software packages, and I've had the opportunity to review most of them. Selecting the best was not easy.
Qtpfsgui came out slightly ahead. It has great tone-mapping and aligning facilities, allows 8,16 and 32 bit channels and two means of manually manipulating the tone-mapping. Qtpfsgui creates a wonderful range of tone-mapped HDR images. When loaded, the images can be aligned either automatically or manually. Click next and a wizard walks you through, but it has recommended profiles or you can change this to get the best profile for your image. It gives you choices for ghosting and response curves, and if these are not to your liking you can tick the custom configuration. After the generated image has been achieved, you have at your disposal a good array of tone-mapped filters and the ability to adjust tone-mapping manually. Here's the big hint; if your computer is struggling to create the TIFF image, make the image in the smallest size. After you adjust your levels and find that you are satisfied with the finished image, delete it (yes, that's right, delete it!) and create your large one. This is not just Windows software; it can be used on Linux and Mac operating systems, and it does support the RAW format.
Picturenaut provides (all automatically) image alignment, exposure correction, color balancing, noise level compensation, and derivation of the camera curve from the source images. Although it doesn't support bracketed RAW images, the many HDR formats it does support are:
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)
What is interesting is that this software provides a choice of "weighting" when you have loaded your images, offering options "Derivative", "+hat1", and "+hat2".
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, though this may be included in a later version.
FDRTools Basic was close to being my first choice because you are able to use the RAW format, and alter the image alignment. 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 is identical, but with the added bonus of compression and brightness. Personally, I work on 'Receptor' because it gives the greater effect if needed. Please delve into the 'Preferences', rather than work with the applications defaults, 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. An excellent program.
The next two software packages are neck-and-neck:
EasyHDR Basic has the edge, in my opinion (probably because I am biased about seeing the curve rather than a slide affect), because I could manipulate the curve. When you load your picture, it will most likely be larger than the screen, so the adjustment zoom is available at the bottom. You will see three tabs showing the three steps you must follow to create your HDR image. The first step is to load your images, and there are two ways to achieve this: 1) load them together, without an option to offset the images, and 2) load them individually, with the ability to move the images for alignment or misalignment. The second step allows you to adjust your image curve, true mapping, and gamma and saturation. Its not obvious, but select an area large enough for you to see the changes and adjustments you make. The third step offers image filters and color adjustments.
Photomatix Basic is really on par with the above. You can download the "Pro" version on a trial basis, but all the functions that are in the "Basic" version will not produce watermarks and will not expire. Photomatix Basic provides the ability to combine two images as an image average, or combine by highlights and shadows. On the HDR, Photomatix will try to align the images for you, with the ability to compensate for moving images. You are advised to take the recommended tone curve of color profile, but the other choice (not the bottom as it does not work on the basic) which is the reverse. When my test images were generated I found that all my own trials had become too dark, and I had to increase the exposure. But when you go on to tone-mapping, the brightness can be adjusted, the tone mapping done with tonal range compression and contrast adaptation. The output is 8 bit, but this can be changed to 16 bit.
Qtpfsgui
Website: http://qtpfsgui.sourceforge.net/
Download size: 3.6MB
License: Open Source
Operating Systems: Linux, Windows and Mac OS X
System requirements: None stated
Languages: It comes in many languages
Picturenaut
Website: http://www.hdrlabs.com/picturenaut/index.html
License: Freeware
Download size: 1.94 MB
Operating System: Windows 98 / ME / 2000 / XP / Vista
Language: English, German
FDRTools Basic
Website: http://fdrtools.com/fdrtools_basic_e.php
Download size: Windows 8MB – OS X 13MB
License: Freeware
Operating Systems: at least Windows 98 or OS X 10.3
System requirements: at least 512 MB memory – Processor: at least Pentium 4, PowerPC G4
EasyHDR Basic
Website: http://www.easyhdr.com/?basic=yes
Download size: 1.37MB
License: Freeware
Operating Systems: any Windows (95/98/XP/Vista)
System requirements: Screen resolution: 1024x768 or higher – Memory: Recommended minimum: 512MB.
Languages: English, Polish, German, French, Portuguese and Italian
Photomatix
Website: http://www.hdrsoft.com/download.html
Download size: 2.6MB
License: Freeware
Operating Systems: Windows 98/ME/2000/XP/Vista (note for MAC download the 'Pro' version as it will work on the basic functions without a watermark)