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Playing with HDR ... - He's just this guy, you know.

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Schlock Mercenary
Something Positive
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Sluggy Freelance

June 29th, 2008

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02:55 am - Playing with HDR ...
I have a new toy. It goes by a name only a geek could love - "qtpfsgui" - a name that tells you in great detail what it is, and almost nothing about what it does. Briefly, it lets me do two things - first, combine two (or more) differing exposures of the same scene to form a High Dynamic Range (HDR) image, and second, performing "tone-mapping" on that image to allow it to be viewed as a normal non-HDR image again (e.g. in JPEG format).

In this case, the first image below was as it came from my camera - it looks like the camera has exposed it well for the sky (the clouds are nicely detailed), but left the rest somewhat under-exposed. The second image (to its right, assuming your browser window is wide enough (and hopefully not blowing up anyone's friends page if not - please let me know!)) was simply created using The GIMP (*sigh* another geeky name ...) by brightening the first image until a fair amount of the shadow detail on the walls was visible. I loaded those images into qtpfsgui, then used the tone-mapping function there to create a best-of-both-worlds version that has most of the detail of both, in the third image.[1]

I did the same for a photo of Dunrobin Castle (below the cut) - again, I had the same sort of slightly under-exposed starting image, created a brighter copy, then ran the HDR/tone-mapping to create the third image of the second set. qtpfsgui has a number of different tone-mapping transformations to use, and suggests that you try all of them until you get close to the desired result. The final photo of Dunrobin shows that not all of the tone-mapping algorithms produce ... "normal" results, although it's still a strangely interesting image.

(as always, all images here are linked to larger versions)

Base image, Broch of Gurness Brighter image, Broch of Gurness

HDR/tone-mapped image, Broch of Gurness

Base image, Dunrobin Castle Brighter image, Dunrobin Castle

HDR/tone-mapped image, Dunrobin Castle

HDR/tone-mapped Dunrobin, different algorithm

[1] (as a side-note, this photo was taken from about 4 metres above ground - camera on top of fully-extended tripod, with me setting the self-timer on the camera, then heaving the tripod up in the air by the bottom of the legs - it worked surprisingly well)

Current Mood: creativecreative

(3 touches | En garde !)


[User Picture]
Date:June 29th, 2008 08:44 pm (UTC)
That last one is very cool! Sort of Starry Night-ish. Looks like it would be a great cover for a YA fantasy novel :-)
[User Picture]
Date:June 29th, 2008 09:31 pm (UTC)

Why do I have a sudden urge to overlay a 50-66% transparent overlay of the last image on the second to last (although I'd probably cut it so that the trees and cars aren't quite so virulent).

Nope. Still don't know why I wanted to do that...

Edited at 2008-06-29 09:34 pm (UTC)
[User Picture]
Date:June 30th, 2008 02:13 am (UTC)

I like how in the first shot, the resulting image of the walls within the shadows closest to the viewer are brighter than either of the source images, and that very last experiment would be great either as an animation backdrop, or to scroll the final credits of a Lord Peter Wimsey or similar 20s/30s whodunnit over ...

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