A new HDR file format seemingly popped out of nowhere, just when we were discussing HDPhoto here. XDepth is aiming at the same thing: efficient compression of HDR images, so they can be distributed over the web. Or take up less storage space - we all know how HDR files eat through your drive, especially when you're dealing with image sequences.

Admittedly, I was a little skeptical about this format. The publisher is very secretive about their encoding approach, sounds like the format is proprietary. And the publisher's name, "Trellis Management Co. Ltd.", doesn't really give me a warm fuzzy feeling either. They actually had another HDR format out for almost a year, called "CLARITY-HDR^TM but aside from the initial announcement I haven't seen it anywhere.

That being said, here is the scoop: XDepth is amazing! It combines the best things of JPEG-HDR and HDPhoto: It's backwards-compatible with JPEG and instantly usable with a free Photoshop Plugin. And after an initial test, it even seems to beat both of them in the amount of compression. Well done, Trellis!

But first things first - here is what the Photoshop saver looks like:

XDepth's Photoshop Saver Dialog: Well organized and usable by mere mortals.

Notice the separation of HDR and LDR compression. When you save your image as XDepth file, the saver will actually make a regular 8-bit JPG, and hide the HDR data in the matadata. That's right - even though the native file extension is .xdp, you can just rename it to .jpg and it will open anywhere. In fact, the XDepth website itself is made of nothing but these renamed .xdp files, making it the first truly HDR online presence on the web.
In the context of this dialog, LDR quality sets the compression of this base-JPG, and the Gamma value is your crude tonemapping control, letting you choose how contrasty you want in this JPEG. The default value 2.2 corresponds to the default settings in Photoshop's 32-bit Preview.

The interesting part comes in when you re-open the file in Photoshop. Then all the hidden HDR data comes back, and find yourself in 32-bit mode.

So let's see how the format compares, using the good old Kitchen Window again.
To include my current favorite, Ward's JPEG-HDR, I pulled it up in Photosphere (for the lack of a Photoshop Plugin, which is in real life a deal breaker by itself).

It turns out, XDepth beats JPEG-HDR and HDPhoto in filesize, although it doesn't look quite as clean. "Lossless" in the saver dialog apparently means "perceptually lossless", not absolutely lossless. In that regard, XDepth will certainly not make OpenEXR obsolete for images that we still need to work with.

However, that isn't what XDepth is aiming at - it is more of a final output format, like JPEG. It is supposed to crunch stuff as small as it gets, while still looking acceptable.

And this is where XDepth's strength is at: Just a tiny wiggle on the quality slider, to 90/95%, will shrink that EXR from 5.7 MB to 344 kB. That's only 1/17th of the size!! And it still looks fine.
Just for the sake of it, I tried to get the HDPhoto to the same file size, and ended up at 48% quality. At this point, the image turns into cubist masterpiece of artifacts.

Bottom line is: XDepth offers an impressive compression ratio, and usability is very straight-forward. The format has all it takes to become the standard for high dynamic range JPEG, clearing the path for a smooth transition to the promised land of All Things HDRI.
However, the catch is Licensing and application support. For now, Trellis Management Co. Ltd. seems to be friendly enough to provide us the tools for free. My wild guess is, they won't make it all open like OpenEXR, instead they will tackle one application at a time and implement import/export plugins themselves. And then, in stage 2, when everyone calls for direct hardware support, they will ask camera and screen makers for licensing fees. I might be entirely wrong here, but if I'm not: Good luck, Trellis, I really hope you succeed! Your format is simply too nice to get lost in some legal grind.

So go grab the Photoshop Plugin from the XDepth website and start playing with it!

Let's talk about HD Photo, the file format formerly known as Windows Media Photo (WDP), and just recently renamed in JPEG-XR. Confused? Yes, me too.

It's a new HDR format, that has been in the works for several years now. I mentioned it on pages 59/60 in my book, but for the lack of any single software that can actually read or write such files, it was excused from the file format comparison chart.
But now things have changed...

HD Photo works now!

Now you can download a free Photoshop plugin for Windows and OSX.
An unexpected and very generous move from Microsoft, not to leave the Mac folks out and even providing the source code. Very cool, thank you! Once installed, the Photoshop plugin works like a charm. While in 32-bit mode you get WDP as a Save option, and it gives you:

• Variable wavelet compression, very much akin to JPEG2000
• Alpha channels, that can have a separate compression
• Embedded color profiles and metadata

For example, an OpenEXR file with an Alpha channel could be crunched down from 6 to 1.4 MB - with no visual losses whatsoever. It might not be mathematically lossless (although that is an option), but visually there it looks clean and artifact-free. And I can load that WDP image back into Photoshop, and start playing with the exposure slider. You can try for yourself: go ahead and download this image in WDP-format.



Pretty impressive. True HDRIs, small enough for email or display on the web. Begs the question:

Why isn't everyone using it?

I don't know. You would think at least Microsoft products take advantage of the HDR-data in an HD Photo. Ha, you're so wrong! Neither the HDView panorama viewer, nor Windows Live Photo Gallery can rock HD Photo right.

They both are new products, both based on WDP as their native format. They just don't know how to deal with high dynamic range images, and so they simply do not work as expected.
Especially Live Photo Gallery was a disappointment, because after a horrifying setup procedure it simply doesn't work as advertised in Bill Crow's Blog. His example might not be such an extreme case like mine, highlights he recovers are still within the realms of what you get in a single RAW file.

If Microsoft doesn't fully utilize the strengths of HD Photo, why should anyone else do?

Maybe it was a pretty bold move to sketch out an entirely new format, and trying to rely on Microsoft's market position to push it through. Maybe Greg Ward was right, when he promotes a soft transition to HDR by providing a backwards-compatible JPEG format:

"Backwards-compatible HDR formats are a win-win for manufacturers and consumers alike. Easing the transition from 24-bit RGB to full dynamic-range and gamut capture, editing, and viewing has the potential to greatly accelerate market penetration. Early adopters would gain immediate access to an HDR world, while others would not be inconvenienced, and could even benefit from improved tone-mapping in their legacy content."

(From The Hopeful Future of HDRI)

Bottom line is: HD Photo works just fine, but only in Photoshop.

And since it is a brand-new format, support will have to be built up one-by-one.

Ward's (or should I say Dolby's) backwards-compatible JPEG-HDR works everywhere. Even though it is disguised as regular JPEG, and only Photosphere and pfstools can actually see the HDR data within. But I can upload a JPEG-HDR image to Flickr, and it behaves just fine. Nobody is inconvenienced, everybody can see it, it gets thumbnailed, and the Flickr people don't have to revamp their entire database system to support a brand-new file format.
But you, my dear HDR-savvy reader, you can just download the Original size image from Flickr, load it in Photosphere, save it back as EXR and tonemap all day long.

Greg Ward, one of the most visionary imaging scientists, has published an excellent paper on the future of HDRI.


He gives all the reason why Digital Imaging is destined to evolve towards HDRI, and he outlines the plan how this transition will actually happen. Given the fact, that Ward developed half of the available HDR image formats, built the world's first HDR display, and is currently on Dolby Lab's salary list, this man certainly knows what he is talking about!

Give yourself the treat of total enlightenment and read his fascinating paper.

This month I have quite a bunch of updates to the site:

Panorama Calculator

How many images do you need for a panorama? Can you streamline the process with a different lens? What if you'd choose less overlap than the "safe" standard 25% ? How does fisheye lens compare to a regular lens?
All these questions are easy to answer with the new Panorama Calculator in the tools section.

Picturenaut FAQ

Documentation is key for every software. Well, Picturenaut doesn't really have a manual, but this FAQ should answer most of your questions. None of the boring bloat stuff - only what you really want to know.

...and the regular monthlies

Back with a brand-new SmartIBL preset, nice and high-res. The Hot-on-Flickr gallery has been reset for February. And the Software Link Directory has been cleaned up to look a bit nicer in your browser.

Have fun,
Christian Bloch
Author/Webmaster/CG-Artist

The word is out from Kevin Connor, top manager at Adobe (so high that even John Nack calls him "boss"). He is The Man behind Photoshop, Lightroom, and the DNG format, and he was questioned about the future roadmap by Steven Shankland at Macworld. Of HDR, Connor said,
"It's definitely a natural thing to do. I don't know when. At some point, cameras will be capturing HDR. At some point, Lightroom will have support for that."

Good to know the chief knows where Digital Imaging is heading.
Read the full article at CNET News...