Introduction

One of my favorite shots of the past week was that of a late 19th century shopping mall in the Dutch city of The Hague called “De Passage”. The place was built in- or around the same time as the famous Galleria Vittorio Emanuele II in Milano, Italy. The styles are comparable as well, a mix of Neo-Renaissance and expressionist styles.

I decided to try to show how I got to this result by two different routes; the first using a mix of commercial and free software and the second consisting of a totally open-source and free workflow. I feel both routes actually led to an extremely similar result, with minor details being treated slightly differently by the software used. The first step of the process also ended up dictating slightly different treatment further down the line.

All software used is available on all three major operating systems, Windows, Apple OS X and the OS I use which is Linux (Manjaro in my case).

Software versions:

• Photomatix  for Linux v22.0 by HDRsoft Ltd
• NeatImage Pro Edition v9.0.0 (64 bit)
• Darktable v3.8.1
• Digikam v7.5.0
• LuminanceHDR v2.6.1

And I used Gimp v2.10.30 to make the screenshot combinations for this article.

End results compared

Let me start with a side-by-side screenshot of both end results, for now not saying which image is the result of which workflow. Let’s just say there definitely are subtle differences in color temperature and contrast but it seems a matter of taste as well as individual skill to bring these end results even closer together. I stopped tweaking at this stage but could have gone on even further – I saw no benefit to go beyond this stage.

The base material

I started out with these 3 hand-held exposures, shot on a Pentax KP with a Sigma 8-16mm ultrawide zoom lens. The three exposures were, from left to right, a third stop underexposed, two stops underexposed and one and a third stop overexposed. This was done to capture as much of the dynamic range as possible on a beautiful sunny afternoon outside with artificial lighting inside.

Aligning, merging and tone mapping the three exposures

As the shots were hand-held, tiny movements between shots will affect the final image sharpness and cause “ghosting” or slightly double contours of edges in the combined image. The software used will detect a large number of corresponding details in all of the images and will overlay them such that ghosting is avoided after which all of the tonal ranges from all three exposures are combined into a final combined image. This creates a so-called high dynamic range or HDR image. This image has details from each of the three exposures but there is such an amount of detail involved that this can neither be shown on-screen or printed. An extra step is needed, the “tone mapping” stage where specific algorithms will compress the large amount of image data into a compressed tonal range suitable to be viewed or printed.

At the initial merging stage, both of the software packages used performed equally well (and almost with the same processing speed too) but the various tone mapping algorithms are quite incomparable. At this stage we are looking for a rough version so this should not be a barrier but I have to admit the non-F/OSS package used (Photomatix) on the left was a lot more predictable in selecting the algorithm versus the final output. Photomatix was also faster in tone mapping and storing the result than the F/OSS software, LuminanceHDR, shown here on the right. One more small observation was that it seems the available screen area was better used by Photomatix, leaving more of the image to be judged. Previews were relatively instantaneous in Photomatix where recalculating a different tone map was quite lethargic at times in LuminanceHDR.

Processing the LDR output

So here I used the same free software for both tone mapping outputs even though I had to change the parameters used on each base image quite a lot to get to a comparable end-result. I’d have to admit that the Photomatix image needed less tweaking of levels, curves and white balance.

The Photomatix output in Darktable

The LuminanceHDR output in Darktable

The last step, noise reduction and sharpening

Non-free: NeatImage

For the non-free workflow I used NeatImage, a reasonably priced cross-platform software package available for Windows, Linux and Apple OS X. This has become my go-to software for final sharpening due to the fact it analyzes the image and finetunes the sharpening and noise reduction variable in accordance with the amount of noise in the image. The square outlines an area that already had a preview of noise reduction and sharpening applied versus the surrounding original image.

Free software: Digikam/Showphoto

Digikam is a free digital asset management (DAM) package with built-in image editor. Digikam is, again, available for all three major computer operating systems. It has powerful sharpening and refocus functions but somewhat weaker noise reduction facilities than NeatImage. As long as I kept that in mind by doing part of the noise reduction in the preceding Darktable step (DT’s profiled wavelet noise reduction is quite powerful), this did not present too much of a challenge.

The end results

Free software workflow

Non-free software workflow

Conclusions

I have to admit that I found the workflow using two commercial packages (Photomatix and NeatImage) slightly faster in operation and quite a bit easier to steer in the direction I wanted – let’s call it predictability. Having said that, I’ve grown a bit lazy over the years and I have shown that both options can in the end deliver quite comparable results. The quality of those results on the open-source software side is more dependent on operator skill. Even though I am an open source veteran of twenty plus years, I truly enjoyed working with Photomatix and NeatImage. Part of the charm is the fact both software companies, even though they focus operations more on Windows and Apple software, have made native Linux versions of their software available at reasonable and competitive prices, including quite a generous update/upgrade plan.

I can recommend both ways of working and both can and will co-exist in my workflow. I have already seen that certain images will lend themselves better to one workflow than the other. That’s why it is nice to have the choice.

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