Thursday, 21 July 2011

Making HDRs

The High Dynamic Range (HDR) is a very popular effect in the last years (although the idea was born in 1850!). When we take a picture with light extreme conditions (with very high and low lights) is difficult show a equilibrated scene. If we want show clear parts in our photo, the shadows will be very dark. If we want show details in shadows, the clear parts of our photo will be burned.

The human eye, controlled by the brain, can view simultaneously a high dynamic range (blacks and whites living together harmonically). We can simulate it with software through mixing the information of several pictures.

The "tone mapping" is a process for colour HDR pictures. When you export a image to a LDR format ("Low Dynamic Range"), with a false-colour, we could view more details than in our original image.

There are a lot of software and plug-ins for HDR, even there are cameras that shoot directly in HDR mode. I like Qtpfsgui / Luminance HDR.

We can make HDRs with one or several pictures. The typical theory of this is: if you have several JPGs (LDR), you can mix them for create a HDR picture with more information than each single JPG.

You also can use RAW files. These files have more information that JPGs files. RAW files already are HDR files!, so you can use a single RAW as HDR, tone mapping it and finally export at JPG file (LDR, with false-colour).

You can do all these process with Qtpfsgui / Luminance HDR, a open source software and multi-platform.

The initial menu

The menu of mixing layers (I'm sorry, my interface is in Spanish)

The tone-mapping menu (I'm sorry again for the language)

The final result is always astonishing. We can view below different attempts.

The original image

HDR (using Fattal's algorithm)

HDR (using Mantiuk's algorithm)

HDR (mixing several HDRs images as layers in Gimp)

You have a fine control of your images through several parameters.

Tone-mapping parameters. You can see all the algorithms. When you select an algorithm, you can view several parameters for it. I'm sorry, my interface is in "Spanglish" :p.

I like very much this software. I recommend it :)! You can download it from here.

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