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Don’t Let qtpfsgui die!

My SonQtpfsgui is the tongue-thorning acronym that identifies one of the most interesting graphics application of the last years. It was registered two years ago on Sourceforge by Giuseppe Rota who as a student saw a need waiting to be fulfilled and an opportunity for a good project: an Open Source graphic user interface to the HDR/Tonemapping process. There are plenty of HDR/Tonemapping tools out there, some of them free (as in beer, not as in speech). Most of them limited to a few tone mapping operators (TMO). And then there is the scientific community, chruning out new TMOs on a regular basis. Rafal Mantiuk is doing a great job at keeping the command line driven pfstools up to date with the latest scientific developments to which he is a significant contributor himself. But the command line is not what graphic artists are used to, especially in a context in which they need visual feedback when turning the knobs and playing with the different parameters of the TMOs.

Unfortunately, not much has happened with Qtpfsgui in the last half year. Giuseppe asked for help with a new name and maybe an icon. Nothing happened yet. With the help of Roman Bednarik and Alexandre Prokoudine, he mentored Vladimir Smida in a season of usability project. But Giuseppe is now busy with his day job, and so little has been going on in the repository. If there is somebody out there reading who knows C++ and Qt (or who wants to learn it), this is a great and very useful project with a significant number of users.

And it is the only tool that got the conversion from RAW of my son’s beautiful eyes just right. Below is standard RAW processing, with Photoshop.

My Son, original

Qtpfsgui needs you

Qtpfsgui is Giuseppe Rota’s brainchild. It is a graphic user interface (GUI) to pfstools( PFS), a set of powerful HDR/Tonemapping tools developed and maintained as an Open Source project by Grzegorz Krawczyk and Rafal Mantiuk, using the Qt Toolkit (QT).

The acronyms explain the tongue-breaking name for the software. Giuseppe is still looking for alternative name proposals. But more than that, he is looking for HELP!

When he started the project, he was still a student with enough time at hand. Now he is a busy professional and the software needs a new maintainer. And it needs any contribution it can get.

I started writing tutorials for the different pfstools tone mapping operators (TMO) that QTpfsgui makes available, but bumped into serious difficulties. With small images, things were right most of the time. But with large images pushing the limits the results sometimes did not look right. I filed a few bug reports. I dug deeper and found out that the PFS tools are actually working as expected when called from the command line. What can cause such an interaction between the GUI code and the functional code which in itself works? and what can be done?


Qtpfsgui (lead author Giuseppe Rota is open for rebranding ideas) is an HDR/tonemapping workflow tool available for Linux, FreeBSD, Windows and OS X.

It covers HDR creation through the merging of multiple exposures (using hugin’s align_image_stack functionality if the images in the stack are not perfectly aligned). And it does tonemapping, offering a choice of eight tone mapping operators (TMO). This is what I like most about Qtpfsgi: the variety of processing options that it offers. Each TMO has its own strenght and weaknesses, and thus its own fields of application. Try them all, you will find your favorites for the different shooting situations!

We’ll be looking in detail at the individual TMOs in the coming articles.

Common to all of them is that

  • we need an HDR image to start with
  • the image can be subject to a pre tone mapping gamma adjustment

Image to start with

Qtpfsgui can be used to compose HDR images from individual exposures. Or it can load the most common HDR file formats. Last but not least, it also load RAW images straight out of the camera. Granted, RAW images have more dynamic range than JPEG images, but in most cases they are still far away from true HDR. Nevertheless, applying TMO’s to RAW images can yield some stunning results. Dare to experiment!

Also it is important to note that the appropriate TMO settings and the results change depending on the type of image processed. Dare to experiment with all sorts of images and available TMOs!

Pre Tone Mapping Gamma Adjustment

Gamma correction is the application of an exponential function to compress (gamma <1) or expand (gamma>1) the image’s dynamic range. A gamma of 1 leaves it unchanged. Gamma <1 compresses the range, resulting in generally higher contrast and darker images. Gamma > 1 expands the range, resulting in generally brighter and lower contrast images. You will find out during the processing with the selected TMO whether applying a pre tone mapping gamma adjustment improves the image.

Last Warnings Before We Go

Tone mapping is a highly subjective topic. There is no right or wrong – follow your inspiration and develop your own style. Nevertheless, there are a few pitfalls:

Noise: If the source images are affected by noise, it is likely to be amplified by the TMOs. Try to shoot at low ISO, or filter noise in the input image before merging to HDR.

Settings: Don’t expect the settings for one image to do the same magic on a completely different image. Settings are case by case. With time you will develop a feeling for each situation.

Saturation: A lot of tone mapped images are over saturated. Keep an eye on it.

Post processing: You will often want to load your tone mapped image and use simple adjustment layers such as levels and curves in your favorite image editor. The goal of the tone mapping process is to reveal the detail, not to finish the image.