Friday, 24 February 2012

HDR – The next step in the evolution of digital film?

HDR: In image processing, computer graphics, and photography, high dynamic range imaging (HDRI or just HDR) is a set of techniques that allows a greater dynamic range between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods. - Wikipedia 

Tone mapping: A technique used in image processing and computer graphics to map one set of colors to another in order to approximate the appearance of high dynamic range images in a medium that has a more limited dynamic range. -Wikipedia

Pushing the boat out: Photographic stills treated with experimental Tone Mapping and colour grading in post.

Like we said before, we’re not just standing in the middle of a digital revolution; it’s also a digital evolution. DSLR cameras are just another step up this evolutionary ladder (with the release of the Canon C300, we’re already looking at a new kind of camera).

The new buzz word in photographic circles is HDR (high dynamic range) imaging. We remember a time, not so long ago when HDR was "the best kept secrets of Hollywood CG artists". Not anymore...

So what exactly is HDR, in layman's terms? Well, HDR is a technique that results in images that have a far greater range of tonal detail, with both the darker areas and the lighter areas well exposed, say for example you’re shooting a landscape under a bright sunny sky, instead of deciding between a beautifully exposed skyscape or a beautifully exposed landscape, HDR will let you have both. 

HDR enabled cameras do this by taking multiple exposures (at different settings) of the same shot, these are then blended together using specialised software. You do also need to have a camera that is geared up for taking HDR pictures. The results can be nothing short of stunning, although we have seen plenty of examples of poorly executed uses of this technique, seeing what is possible, got us interested in exploring further.

Luckily for us, those guys at Magic Lantern have just released an update to their firmware for Canon cameras that now includes HDR mode for both still and video! That's right, our Canon Rebel T2i/550D is now also a HDR camera.

This first version of the HDR mode is not ideally suited for images with lots of movement, but for images that don’t have a lot of movement, the results are worth getting excited over (we’re thinking of painterly landscapes).

In regards to the software you'll need, Photomatix seems to be one of the most popular and is available as a stand alone program or as a plugin for both Photoshop and Apples' Aperture software, and looks to be pretty straightforward to use, although we use HDR Efex Pro by a company called Nik Software and have been pretty impressed with the results it’s given us.

This production still from All That Remains has had Tone Mapping applied using HDR Efex Pro.
But... we have found a FREE one. It's called EnfuseGUI, and also looks pretty straightforward. We'll do some tests and see which one works best for us.

Talking of tests, we’ll be doing some test shots of HDR applied to video, for our film project, “All That Remains” and will post some of the footage here.


As mentioned up there, in terms of the image processing side of things we’ve also got Tone Mapping, a process that simulates the effect of shooting with HDR for images NOT captured with a HDR camera, and unlike HDR, which expands the tonal range of an image by blending multiple photos taken at different exposure settings, Tone Mapping works with a single image and uses sophisticated algorithms.

Now at first this sounded a bit dubious to us, we envisaged crude, over the top pseudo HDR type images, but we were keen to experiment. After hunting around online for a Tone Mapping plugin for video (unbelievably none of the big names in plugins seem to be interested in developing one for Tone Mapping), we found one, and for Adobe After Effects too, our grading software of choice!. The plugin is called Ginger HDR and it’s from a company called 19 Lights, and it’s still in beta stages, but it is available for download – free. So, of course we downloaded it.

Within a few moments of playing around with it, we were impressed. In fact we were really impressed. The images we’d shot, which were all shot on our DSLR using the Technicolor flat picture style, came in looking flat and a little dull (as they are supposed to look pre-grading). When we applied the various settings of the Ginger plugin, the colour and detail popped right out of the screen.

Now, you do have to be careful with Tone Mapping, it’s so easy to push it too hard and go over the top, the key is to go gently and keep checking for increase in image noise or any other artefacts. A small increase in noise is OK, and sometimes it’s a trade off, but only so long as the image isn’t pushed too far and above all, it looks good enough to be worth it. 

We've done some testing with Tone Mapping in After Effects.....

Before and after: The raw image is brought into Adobe After Effects where the Ginger HDR plugin is applied.
We found that HDR techniques are capable of producing a more painterly image, which suits our visual style, so we’ll definitely be implementing it in the filming and post-production workflow of “All That Remains”.
Above is a shot from “All That Remains” going through the grading process. This shot has had the tone mapping technique applied to it, as well as other colouring work and a spot of digital re-lighting.
On the strength of the results we’ve seen so far from our own experiments, and some of the examples we’ve seen online, we’re pretty sure the next generation of cameras will come with special “HDR” modes included. Lucky for us, we’ve got Magic Lantern…