timeimmortal

This is perhaps my first successful attempt at HDR (high dynamic range) photography, and gives me the opportunity to mention a new piece of image-editing software in my arsenal: Qtpfsgui.

Quite a mouthful, no? Yes, it is, but it does work rather well.

Creating HDR images is a rather involved process. It begins with taking a series of shots of the desired subject — in this case, I took three images of the building, from this angle, in rapid succession. One was normally exposed, and the other two were exposed at, respectively, -2 eV and +2 eV (meaning one was underexposed, so that the details in the sky were well-captured, and the other was overexposed, so the details of the building were well-captured). The normal shot was mostly done to provide colour information, I guess.

Anyhow, the first-pass editing was done in Lightroom, in which each image was edited for things like chromatic aberration, digital noise, and the like. Basic colour adjustments were also done, and the three images were exported as TIFF files.

Next came Qtpfsgui. I loaded each image into the program and told it to use Hugin’s algorithims to auto-align them to each other. Once it had done this, I ran the default HDR generation protocol in the program, and it generated an initial HDR image for me. Of course, the image looked a little bit flat and uninteresting when rendered on screen, so I had to do some tone mapping to get the result that can be seen here.

Said result was generated by using, if memory serves, an algorithm called Mantiuk, and generating two images. One was oversaturated, and carried the colour information for the tone mapped image. The other was greyscale, but carried all the contrast/detail information for the image. These were exported as PNG images, if memory serves.

The third round of editing was done with Photoshop, in which I layered the two images atop each other, set the transparency of the top image (the oversaturated image) to 59%, and then ran Photoshop’s automatic colour, contrast, and tone processing options on the result. I also, just for fun, added in the lens flare using Photoshop’s rendering functions, although in my defence the 17-85 mm lens had actually generated some (uglier) flare in the image to begin with — I was trying to hide this.

Notable flaws with the image are the noise grain introduced by the high-contrast Mantiuk tone mapped image, which could not be avoided. I’m still messing around in Qtpfsgui to see if I can get a better combination of images which will give similarly good results in terms of colour and detail, but for the moment this seems to be the best option available to me.

At any rate, it’s a first successful HDR image for me, so expect to see a few more images of this nature in the future.

~ by Kenneth on June 13, 2008.